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KSH(1)                                                                  KSH(1)



NAME
       ksh, rksh, pfksh - KornShell, a standard/restricted command and programming language

SYNOPSIS
       ksh [ ?abcefhiknoprstuvxBCDP ] [ -R file ] [ ?o option ] ... [ - ] [ arg ... ]

DESCRIPTION
       Ksh  is  a  command  and programming language that executes commands read from a terminal or a file.  Rksh is a
       restricted version of the command interpreter ksh; it is used to set up login names and execution  environments
       whose  capabilities are more controlled than those of the standard shell.  Rpfksh is a profile shell version of
       the command interpreter ksh; it is used to to execute commands with the attributes specified by the user's pro-
       files (see pfexec(1)).  See Invocation below for the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )   |   <   >   new-line   space   tab

       A  blank  is  a tab or a space.  An identifier is a sequence of letters, digits, or underscores starting with a
       letter or underscore.  Identifiers are used as components of variable names.  A vname is a sequence of  one  or
       more  identifiers  separated  by  a . and optionally preceded by a ..  Vnames are used as function and variable
       names.  A word is a sequence of characters from the character set defined by the current locale, excluding non-
       quoted metacharacters.

       A  command  is  a sequence of characters in the syntax of the shell language.  The shell reads each command and
       carries out the desired action either directly or by invoking separate utilities.  A built-in command is a com-
       mand  that  is carried out by the shell itself without creating a separate process.  Some commands are built-in
       purely for convenience and are not documented here.  Built-ins that cause side effects in the shell environment
       and  built-ins  that  are found before performing a path search (see Execution below) are documented here.  For
       historical reasons, some of these built-ins behave differently than other  built-ins  and  are  called  special
       built-ins.

   Commands.
       A simple-command is a list of variable assignments (see Variable Assignments below) or a sequence of blank sep-
       arated words which may be preceded by a list of variable assignments (see Environment below).  The  first  word
       specifies the name of the command to be executed.  Except as specified below, the remaining words are passed as
       arguments to the invoked command.  The command name is passed as argument 0 (see exec(2)).  The value of a sim-
       ple-command  is  its  exit status; 0-255 if it terminates normally; 256+signum if it terminates abnormally (the
       name of the signal corresponding to the exit status can be obtained via the -l  option  of  the  kill  built-in
       utility).

       A  pipeline  is a sequence of one or more commands separated by |.  The standard output of each command but the
       last is connected by a pipe(2) to the standard input of the next command.  Each command,  except  possibly  the
       last,  is  run  as a separate process; the shell waits for the last command to terminate.  The exit status of a
       pipeline is the exit status of the last command unless the pipefail option is enabled.  Each  pipeline  can  be
       preceded by the reserved word !  which causes the exit status of the pipeline to become 0 if the exit status of
       the last command is non-zero, and 1 if the exit status of the last command is 0.

       A list is a sequence of one or more pipelines separated by ;, &, |&, &&, or ||, and optionally terminated by ;,
       &,  or  |&.   Of these five symbols, ;, &, and |& have equal precedence, which is lower than that of && and ||.
       The symbols && and || also have equal precedence.  A semicolon (;) causes sequential execution of the preceding
       pipeline;  an  ampersand  (&) causes asynchronous execution of the preceding pipeline (i.e., the shell does not
       wait for that pipeline to finish).  The symbol |& causes asynchronous execution of the preceding pipeline  with
       a  two-way  pipe  established to the parent shell; the standard input and output of the spawned pipeline can be
       written to and read from by the parent shell by applying the redirection operators <& and >& with arg p to com-
       mands  and  by  using  -p  option  of the built-in commands read and print described later.  The symbol && (||)
       causes the list following it to be executed only if the preceding pipeline returns  a  zero  (non-zero)  value.
       One  or  more  new-lines may appear in a list instead of a semicolon, to delimit a command.  The first item  of
       the first pipeline of a list that is a simple command not beginning  with  a  redirection,  and  not  occurring
       within a while, until, or if list, can be preceded by a semicolon.  This semicolon is ignored unless the showme
       option is enabled as described with the set built-in below.

       A command is either a simple-command or one of the following.  Unless otherwise stated, the value returned by a
       command is that of the last simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
              Each  time  a for command is executed, vname is set to the next word taken from the in word list.  If in
              word ...  is omitted, then the for command executes the do list once for each positional parameter  that
              is  set starting from 1 (see Parameter Expansion below).  Execution ends when there are no more words in
              the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The arithmetic expression expr1 is evaluated first (see Arithmetic evaluation  below).   The  arithmetic
              expression  expr2 is repeatedly evaluated until it evaluates to zero and when non-zero, list is executed
              and the arithmetic expression expr3 evaluated.  If any expression is omitted, then it behaves as  if  it
              evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A  select command prints on standard error (file descriptor 2) the set of words, each preceded by a num-
              ber.  If in word ...  is omitted, then the positional parameters starting from 1 are used  instead  (see
              Parameter  Expansion  below).  The PS3 prompt is printed and a line is read from the standard input.  If
              this line consists of the number of one of the listed words, then the value of the variable vname is set
              to  the  word corresponding to this number.  If this line is empty, the selection list is printed again.
              Otherwise the value of the variable vname is set to null.  The contents of the line read  from  standard
              input  is saved in the variable REPLY.  The list is executed for each selection until a break or end-of-
              file is encountered.  If the REPLY variable is set to null by the execution of list, then the  selection
              list is printed before displaying the PS3 prompt for the next selection.

       case word in [ [(]pattern [ | pattern ] ... ) list ;; ] ... esac
              A  case  command executes the list associated with the first pattern that matches word.  The form of the
              patterns is the same as that used for file-name generation (see File Name  Generation  below).   The  ;;
              operator  causes execution of case to terminate.  If ;& is used in place of ;; the next subsequent list,
              if any,  is executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit status, the list  following  the  first
              then  is  executed.   Otherwise, the list following elif is executed and, if its value is zero, the list
              following the next then is executed.  Failing each successive elif list, the else list is executed.   If
              the  if list has non-zero exit status and there is no else list, then the if command returns a zero exit
              status.

       while list ;do list ;done
       until list ;do list ;done
              A while command repeatedly executes the while list and, if the exit status of the last  command  in  the
              list  is  zero,  executes the do list; otherwise the loop terminates.  If no commands in the do list are
              executed, then the while command returns a zero exit status; until may be used  in  place  of  while  to
              negate the loop termination test.

       ((expression))
              The  expression is evaluated using the rules for arithmetic evaluation described below.  If the value of
              the arithmetic expression is non-zero, the exit status is 0, otherwise the exit status is 1.

       (list)
              Execute list in a separate environment.  Note, that if two adjacent  open  parentheses  are  needed  for
              nesting, a space must be inserted to avoid evaluation as an arithmetic command as described above.

       { list;}
              list  is  simply  executed.  Note that unlike the metacharacters ( and ), { and } are reserved words and
              must occur at the beginning of a line or after a ; in order to be recognized.

       [[ expression ]]
              Evaluates expression and returns a zero exit status when expression is true.   See  Conditional  Expres-
              sions below, for a description of expression.

       function varname { list ;}
       varname () { list ;}
              Define  a  function  which is referenced by varname.  A function whose varname contains a .  is called a
              discipline function and the portion of the varname preceding the last  .   must  refer  to  an  existing
              variable.   The  body  of the function is the list of commands between { and }.  A function defined with
              the function varname syntax can also be used as an argument to the .  special built-in  command  to  get
              the equivalent behavior as if the varname() syntax were used to define it.  (See Functions below.)

       namespace identifier { list ;}
              Defines  or  uses the name space identifier and runs the commands in list in this name space.  (See Name
              Spaces below.)

       & [ name [ arg... ]  ]
              Causes subsequent list commands terminated by & to be placed in the background job pool name.   If  name
              is  omitted  a  default  unnamed  pool  is  used.   Commands  in a named background pool may be executed
              remotely.

       time [ pipeline ]
              If pipeline is omitted the user and system time for the current shell and completed child  processes  is
              printed on standard error.  Otherwise, pipeline is executed and the elapsed time as well as the user and
              system time are printed on standard error.  The TIMEFORMAT variable may be set to a format  string  that
              specifies  how  the timing information should be displayed.  See Shell Variables below for a description
              of the TIMEFORMAT variable.

       The following reserved words are recognized as reserved only when they are the first word of a command and  are
       not quoted:

       if then else elif fi case esac for while until do done { } function select time [[ ]] !

   Variable Assignments.
       One  or  more variable assignments can start a simple command or can be arguments to the typeset, enum, export,
       or readonly special built-in commands as well as to other declaration commands created as  types.   The  syntax
       for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and word.

       varname=(assign_list)
              No  space  is permitted between varname and the =.  The variable varname is unset before the assignment.
              An assign_list can be one of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative array assignment.  If preceded by typeset -a  this  will  create  an  indexed
                             array instead.
                      assignment ...
                             Compound  variable  assignment.   This creates a compound variable varname with sub-vari-
                             ables of the form varname.name, where name is the name portion of assignment.  The  value
                             of varname will contain all the assignment elements.  Additional assignments made to sub-
                             variables of varname will also be displayed as part of  the  value  of  varname.   If  no
                             assignments are specified, varname will be a compound variable allowing subsequence child
                             elements to be defined.
                      typeset [options] assignment ...
                             Nested variable assignment.  Multiple assignments can be specified by separating each  of
                             them  with  a  ;.   The previous value is unset before the assignment.  Other declaration
                             commands such as readonly, enum, and other declaration commands can be used in  place  of
                             typeset.
                      . filename
                             Include the assignment commands contained in filename.

       In  addition, a += can be used in place of the = to signify adding to or appending to the previous value.  When
       += is applied to an arithmetic type, word is evaluated as an arithmetic expression and  added  to  the  current
       value.   When  applied  to a string variable, the value defined by word is appended to the value.  For compound
       assignments, the previous value is not unset and the new values are appended to the current ones provided  that
       the types are compatible.

       The  right  hand  side of a variable assignment undergoes all the expansion listed below except word splitting,
       brace expansion, and file name generation.  When the left hand side is an assignment is a compound variable and
       the  right  hand  is  the  name  of  a  compound variable, the compound variable on the right will be copied or
       appended to the compound variable on the left.

   Comments.
       A word beginning with # causes that word and all the following characters up to a new-line to be ignored.
   Aliasing.
       The first word of each command is replaced by the text of an alias if an alias for this word has been  defined.
       An alias name consists of any number of characters excluding metacharacters, quoting characters, file expansion
       characters, parameter expansion and command substitution characters, the characters / and =.   The  replacement
       string  can  contain  any valid shell script including the metacharacters listed above.  The first word of each
       command in the replaced text, other than any that are in the process of being  replaced,  will  be  tested  for
       aliases.   If  the  last character of the alias value is a blank then the word following the alias will also be
       checked for alias substitution.  Aliases can be used to redefine built-in commands but cannot be used to  rede-
       fine  the  reserved  words  listed  above.  Aliases can be created and listed with the alias command and can be
       removed with the unalias command.
       Aliasing is performed when scripts are read, not while they are executed.  Therefore,  for  an  alias  to  take
       effect,  the alias definition command has to be executed before the command which references the alias is read.
       The following aliases are compiled into the shell but can be unset or redefined:
                           autoload=?typeset -fu?
                           command=?command  ?
                           compound=?typeset -C?
                           fc=hist
                           float=?typeset -lE?
                           functions=?typeset -f?
                           hash=?alias -t --?
                           history=?hist -l?
                           integer=?typeset -li?
                           nameref=?typeset -n?
                           nohup=?nohup  ?
                           r=?hist -s?
                           redirect=?command exec?
                           source=?command .?
                           stop=?kill -s STOP?
                           suspend=?kill -s STOP $$?
                           times=?{ { time;} 2>&1;}?
                           type=?whence -v?

   Tilde Substitution.
       After alias substitution is performed, each word is checked to see if it begins with an unquoted ~.  For  tilde
       substitution,  word also refers to the word portion of parameter expansion (see Parameter Expansion below).  If
       it does, then the word up to a / is checked to see if it matches a user name in the password database (See get-
       pwname(3).)   If  a match is found, the ~ and the matched login name are replaced by the login directory of the
       matched user.  If no match is found, the original text is left unchanged.  A ~ by itself, or in front of  a  /,
       is replaced by $HOME.  A ~ followed by a + or - is replaced by the value of $PWD and $OLDPWD respectively.

       In  addition,  when  expanding  a  variable  assignment,  tilde substitution is attempted when the value of the
       assignment begins with a ~, and when a ~ appears after a :.  The : also terminates a ~ login name.

   Command Substitution.
       The standard output from a command list enclosed in parentheses preceded by a dollar sign ( $(list) ), or in  a
       brace  group preceded by a dollar sign ( ${ list;} ), or in a pair of grave accents (``) may be used as part or
       all of a word; trailing new-lines are removed.  In the second case, the { and } are treated as a reserved words
       so  that  {  must  be followed by a blank and } must appear at the beginning of the line or follow a ;.  In the
       third (obsolete) form, the string between the quotes is processed for special  quoting  characters  before  the
       command  is  executed (see Quoting below).  The command substitution $(cat file) can be replaced by the equiva-
       lent but faster $(<file).  The command substitution $(n<#) will expand to the  current  byte  offset  for  file
       descriptor  n.   Except  for the second form, the command list is run in a subshell so that no side effects are
       possible.  For the second form, the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An arithmetic expression enclosed in double parentheses preceded by a dollar sign ( $(()) ) is replaced by  the
       value of the arithmetic expression within the double parentheses.

   Process Substitution.
       Each  command  argument  of  the form <(list) or >(list) will run process list asynchronously connected to some
       file in /dev/fd if this directory exists, or else a fifo a temporary directory.  The name  of  this  file  will
       become  the  argument  to  the  command.  If the form with > is selected then writing on this file will provide
       input for list.  If < is used, then the file passed as an argument will contain the output of the list process.
       For example,

              paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(process2)

       cuts  fields  1 and 3 from the files file1 and file2 respectively, pastes the results together, and sends it to
       the processes process1 and process2, as well as putting it onto the standard output.  Note that the file, which
       is passed as an argument to the command, is a UNIX pipe(2) so programs that expect to lseek(2) on the file will
       not work.

       Process substitution of the form <(list) can also be used with the < redirection operator which causes the out-
       put of list to be standard input or the input for whatever file descriptor is specified.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters *, @, #, ?, -, $, and !.  A variable is
       denoted by a vname.  To create a variable whose vname contains a ., a variable whose vname consists  of  every-
       thing before the last . must already exist.  A variable has a value and zero or more attributes.  Variables can
       be assigned values and attributes by using the typeset special built-in command.  The attributes  supported  by
       the  shell  are  described later with the typeset special built-in command.  Exported variables pass values and
       attributes to the environment.

       The shell supports both indexed and associative arrays.  An element of an array variable  is  referenced  by  a
       subscript.   A subscript for an indexed array is denoted by an arithmetic expression (see Arithmetic evaluation
       below) between a [ and a ].  To assign values to an indexed array, use vname=(value ...) or set -A vname  value
       ...  .   The value of all non-negative subscripts must be in the range of 0 through 4,194,303.  A negative sub-
       script is treated as an offset from the maximum current index +1  so  that  -1  refers  to  the  last  element.
       Indexed arrays can be declared with the -a option to typeset.  Indexed arrays need not be declared.  Any refer-
       ence to a variable with a valid subscript is legal and an array will be created if necessary.

       An associative array is created with the -A option to typeset.  A subscript for an associative array is denoted
       by a string enclosed between [ and ].

       Referencing any array without a subscript is equivalent to referencing the array with subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       Attributes  assigned by the typeset special built-in command apply to all elements of the array.  An array ele-
       ment can be a simple variable, a compound variable or an array variable.  An element of an indexed array can be
       either  an  indexed  array or an associative array.  An element of an associative array can also be either.  To
       refer to an array element that is part of an array element, concatenate the subscript in brackets.   For  exam-
       ple, to refer to the foobar element of an associative array that is defined as the third element of the indexed
       array, use ${vname[3][foobar]}
       A nameref is a variable that is a reference to another variable.  A nameref is created with the -n attribute of
       typeset.  The value of the variable at the time of the typeset command becomes the variable that will be refer-
       enced whenever the nameref variable is used.  The name of a nameref cannot contain a ..   When  a  variable  or
       function  name  contains  a ., and the portion of the name up to the first . matches the name of a nameref, the
       variable referred to is obtained by replacing the nameref portion with the name of the variable  referenced  by
       the nameref.  If a nameref is used as the index of a for loop, a name reference is established for each item in
       the list.  A nameref provides a convenient way to refer to the variable inside a function whose name is  passed
       as  an  argument  to  a  function.  For example, if the name of a variable is passed as the first argument to a
       function, the command
              typeset -n var=$1
       inside the function causes references and assignments to var to be references and assignments to  the  variable
       whose name has been passed to the function.
       If  any  of  the floating point attributes, -E, -F, or -X, or the integer attribute, -i, is set for vname, then
       the value is subject to arithmetic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be assigned values with  the  set  special  built-in
       command.  Parameter $0 is set from argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The  shell  reads  all the characters from ${ to the matching } as part of the same word even if it con-
              tains braces or metacharacters.  The value, if any, of the parameter is  substituted.   The  braces  are
              required  when  parameter is followed by a letter, digit, or underscore that is not to be interpreted as
              part of its name, when the variable name contains a ..  The braces are also required when a variable  is
              subscripted  unless it is part of an Arithmetic Expression or a Conditional Expression.  If parameter is
              one or more digits then it is a positional parameter.  A positional parameter of  more  than  one  digit
              must  be  enclosed in braces.  If parameter is * or @, then all the positional parameters, starting with
              $1, are substituted (separated by a field separator character).  If an array vname with last subscript *
              @,  or  for  index  arrays  of the form sub1 ..  sub2.  is used, then the value for each of the elements
              between sub1 and sub2 inclusive (or all elements for * and @) is substituted,  separated  by  the  first
              character of the value of IFS.
       ${#parameter}
              If  parameter  is  * or @, the number of positional parameters is substituted.  Otherwise, the length of
              the value of the parameter is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${@vname}
              Expands to the type name (See Type Variables  below) or attributes of the variable referred to by vname.
       ${!vname}
              Expands  to  the  name  of the variable referred to by vname.  This will be vname except when vname is a
              name reference.
       ${!vname[subscript]}
              Expands to name of the subscript unless subscript is *, @.  or of the form sub1  ..   sub2.   When  sub-
              script  is *, the list of array subscripts for vname is generated.  For a variable that is not an array,
              the value is 0 if the variable is set.  Otherwise it is null.  When  subscript  is  @,  same  as  above,
              except that when used in double quotes, each array subscript yields a separate argument.  When subscript
              is of the form sub1 ..  sub2 it expands to the list of subscripts between sub1 and sub2 inclusive  using
              the same quoting rules as @.
       ${!prefix*}
              Expands to the names of the variables whose names begin with prefix.
       ${parameter:-word}
              If parameter is set and is non-null then substitute its value; otherwise substitute word.
       ${parameter:=word}
              If  parameter is not set or is null then set it to word; the value of the parameter is then substituted.
              Positional parameters may not be assigned to in this way.
       ${parameter:?word}
              If parameter is set and is non-null then substitute its value; otherwise, print word and exit  from  the
              shell (if not interactive).  If word is omitted then a standard message is printed.
       ${parameter:+word}
              If parameter is set and is non-null then substitute word; otherwise substitute nothing.
       In  the above, word is not evaluated unless it is to be used as the substituted string, so that, in the follow-
       ing example, pwd is executed only if d is not set or is null:
              print ${d:-$(pwd)}
       If the colon ( : ) is omitted from the above expressions, then the shell only checks whether parameter  is  set
       or not.
       ${parameter:offset:length}
       ${parameter:offset}
              Expands  to the portion of the value of parameter starting at the character (counting from 0) determined
              by expanding offset as an arithmetic expression and consisting of the number of characters determined by
              the  arithmetic  expression  defined by length.  In the second form, the remainder of the value is used.
              If A negative offset counts backwards from the end of parameter.   Note  that  one  or  more  blanks  is
              required in front of a minus sign to prevent the shell from interpreting the operator as :-.  If parame-
              ter is * or @, or is an array name indexed by * or @, then offset and length refer to  the  array  index
              and  number of elements respectively.  A negative offset is taken relative to one greater than the high-
              est subscript for indexed arrays.  The order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If the shell pattern matches the beginning of the value of parameter, then the value of  this  expansion
              is the value of the parameter with the matched portion deleted; otherwise the value of this parameter is
              substituted.  In the first form the smallest matching pattern is deleted and  in  the  second  form  the
              largest  matching  pattern is deleted.  When parameter is @, *, or an array variable with subscript @ or
              *, the substring operation is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If the shell pattern matches the end of the value of parameter, then the value of this expansion is  the
              value  of  the parameter with the matched part deleted; otherwise substitute the value of parameter.  In
              the first form the smallest matching pattern is deleted and in the second form the largest matching pat-
              tern  is  deleted.   When  parameter  is @, *, or an array variable with subscript @ or *, the substring
              operation is applied to each element in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of pattern with the given string.  Each  occurrence  of
              \n  in  string  is replaced by the portion of parameter that matches the n-th sub-pattern.  In the first
              form, only the first occurrence of pattern is replaced.  In the second form, each match for  pattern  is
              replaced by the given string.  The third form restricts the pattern match to the beginning of the string
              while the fourth form restricts the pattern match to the end of the string.  When string  is  null,  the
              pattern  will  be  deleted  and  the / in front of string may be omitted.  When parameter is @, *, or an
              array variable with subscript @ or *, the substitution operation is applied to each element in turn.  In
              this case, the string portion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set command.
              ?      The decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially, the value of _ is an absolute pathname of the shell or script being executed as passed
                     in the environment.  Subsequently it is assigned the last argument of the previous command.  This
                     parameter  is  not  set for commands which are asynchronous.  This parameter is also used to hold
                     the name of the matching MAIL file when checking for mail.  While defining a compound variable or
                     a  type,  _  is  initialized  as a reference to the compound variable or type.  When a discipline
                     function is invoked, _ is initialized as a reference to the variable associated with the call  to
                     this  function.   Finally  when _ is used as the name of the first variable of a type definition,
                     the new type is derived from the type of the first variable (See Type Variables  below.).
              !      The process id or the pool name and job number of the last background command invoked or the most
                     recent  job  put  in  the  background with the bg built-in command.  Background jobs started in a
                     named pool will be in the form pool.number where pool is the pool name and number is the job num-
                     ber within that pool.
              .sh.command
                     When  processing  a  DEBUG trap, this variable contains the current command line that is about to
                     run.
              .sh.edchar
                     This variable contains the value of the keyboard character (or  sequence  of  characters  if  the
                     first character is an ESC, ascii 033) that has been entered when processing a KEYBD trap (see Key
                     Bindings below).  If the value is changed as part of the trap action, then the new value replaces
                     the key (or key sequence) that caused the trap.
              .sh.edcol
                     The character position of the cursor at the time of the most recent KEYBD trap.
              .sh.edmode
                     The  value  is  set to ESC when processing a KEYBD trap while in vi insert mode.  (See Vi Editing
                     Mode  below.)  Otherwise, .sh.edmode is null when processing a KEYBD trap.
              .sh.edtext
                     The characters in the input buffer at the time of the most recent KEYBD trap.  The value is  null
                     when not processing a KEYBD trap.
              .sh.file
                     The pathname of the file than contains the current command.
              .sh.fun
                     The name of the current function that is being executed.
              .sh.level
                     Set to the current function depth.  This can be changed inside a DEBUG trap and will set the con-
                     text to the specified level.
              .sh.lineno
                     Set during a DEBUG trap to the line number for the caller of each function.
              .sh.match
                     An indexed array which stores the most recent match and  sub-pattern  matches  after  conditional
                     pattern  matches  that  match and after variables expansions using the operators #, %, or /.  The
                     0-th element stores the complete match and the i-th.  element  stores  the  i-th  submatch.   The
                     .sh.match variable becomes unset when the variable that has expanded is assigned a new value.
              .sh.math
                     Used for defining arithmetic functions (see Arithmetic evaluation below).  and stores the list of
                     user defined arithmetic functions.
              .sh.name
                     Set to the name of the variable at the time that a discipline function is invoked.
              .sh.subscript
                     Set to the name subscript of the variable at the time that a discipline function is invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the variable at the time that  the  set  or  append  discipline  function  is
                     invoked.  When a user defined arithmetic function is invoked, the value of .sh.value is saved and
                     .sh.value is set to long double precision floating point.  .sh.value is restored when  the  func-
                     tion returns.
              .sh.version
                     Set to a value that identifies the version of this shell.
              KSH_VERSION
                     A name reference to .sh.version.
              LINENO The current line number within the script or function being executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The value of the last option argument processed by the getopts built-in command.
              OPTIND The index of the last option argument processed by the getopts built-in command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each  time  this  variable  is  referenced, a random integer, uniformly distributed between 0 and
                     32767, is generated.  The sequence of random numbers can be initialized by  assigning  a  numeric
                     value to RANDOM.
              REPLY  This  variable  is set by the select statement and by the read built-in command when no arguments
                     are supplied.
              SECONDS
                     Each time this variable is referenced, the number of seconds since shell invocation is  returned.
                     If  this  variable  is assigned a value, then the value returned upon reference will be the value
                     that was assigned plus the number of seconds since the assignment.
              SHLVL  An integer variable the is incremented each time the shell is invoked and is exported.  If  SHLVL
                     is not in the environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If  this  variable is set, the value is used to define the width of the edit window for the shell
                     edit modes and for printing select lists.
              EDITOR If the VISUAL variable is not set, the value of this variable will be checked for the patterns as
                     described  with VISUAL below and the corresponding editing option (see Special Command set below)
                     will be turned on.
              ENV    If this variable is set, then parameter expansion, command substitution, and arithmetic substitu-
                     tion are performed on the value to generate the pathname of the script that will be executed when
                     the shell is invoked interactively (see Invocation below).  This file is typically used for alias
                     and  function  definitions.  The default value is $HOME/.kshrc.  On systems that support a system
                     wide  /etc/ksh.kshrc initialization file, if the filename  generated  by  the  expansion  of  ENV
                     begins with /./ or ././ the system wide initialization file will not be executed.
              FCEDIT Obsolete name for the default editor name for the hist command.  FCEDIT is not used when HISTEDIT
                     is set.
              FIGNORE
                     A pattern that defines the set of filenames that will be ignored when performing filename  match-
                     ing.
              FPATH  The  search  path for function definitions.  The directories in this path are searched for a file
                     with the same name as the function or command when a function with the -u attribute is referenced
                     and  when  a command is not found.  If an executable file with the name of that command is found,
                     then it is read and executed in the current environment.  Unlike PATH, the current directory must
                     be  represented explicitly by .  rather than by adjacent : characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If this variable is set when the shell is invoked, then the value is the  pathname  of  the  file
                     that will be used to store the command history (see Command Re-entry below).
              HISTSIZE
                     If this variable is set when the shell is invoked, then the number of previously entered commands
                     that are accessible by this shell will be greater than or equal to this number.  The  default  is
                     512.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal  field  separators,  normally  space,  tab,  and  new-line that are used to separate the
                     results of command substitution or parameter expansion and to separate fields with  the  built-in
                     command read.  The first character of the IFS variable is used to separate arguments for the "$*"
                     substitution (see Quoting below).  Each single occurrence of an IFS character in the string to be
                     split, that is not in the isspace character class, and any adjacent characters in IFS that are in
                     the isspace character class, delimit a field.  One or more characters in IFS that belong  to  the
                     isspace  character  class,  delimit  a field.  In addition, if the same isspace character appears
                     consecutively inside IFS, this character is treated as if it were not in the  isspace  class,  so
                     that  if  IFS  consists  of  two  tab characters, then two adjacent tab characters delimit a null
                     field.
              JOBMAX This variable defines the maximum number running background jobs that can run at  a  time.   When
                     this limit is reached, the shell will wait for a job to complete before staring a new job.
              LANG   This  variable  determines  the locale category for any category not specifically selected with a
                     variable starting with LC_ or LANG.
              LC_ALL This variable overrides the value of the LANG variable and any other LC_ variable.
              LC_COLLATE
                     This variable determines the locale category for character collation information.
              LC_CTYPE
                     This variable determines the locale category for character handling functions.  It determines the
                     character classes for pattern matching (see File Name Generation below).
              LC_NUMERIC
                     This variable determines the locale category for the decimal point character.
              LINES  If  this  variable  is  set, the value is used to determine the column length for printing select
                     lists.  Select lists will print vertically until about two-thirds of LINES lines are filled.
              MAIL   If this variable is set to the name of a mail file and the MAILPATH variable is not set, then the
                     shell informs the user of arrival of mail in the specified file.
              MAILCHECK
                     This  variable specifies how often (in seconds) the shell will check for changes in the modifica-
                     tion time of any of the files specified by the MAILPATH or MAIL variables.  The default value  is
                     600 seconds.  When the time has elapsed the shell will check before issuing the next prompt.
              MAILPATH
                     A  colon ( : ) separated list of file names.  If this variable is set, then the shell informs the
                     user of any modifications to the specified files that have occurred  within  the  last  MAILCHECK
                     seconds.  Each file name can be followed by a ?  and a message that will be printed.  The message
                     will undergo parameter expansion, command substitution,  and  arithmetic  substitution  with  the
                     variable  $_  defined  as the name of the file that has changed.  The default message is you have
                     mail in $_.
              PATH   The search path for commands (see Execution below).  The user may not change  PATH  if  executing
                     under rksh (except in .profile).
              PS1    The  value of this variable is expanded for parameter expansion, command substitution, and arith-
                     metic substitution to define the primary prompt string which by default is ''$''.  The  character
                     !   in  the primary prompt string is replaced by the command number (see Command Re-entry below).
                     Two successive occurrences of !  will produce a single !  when the prompt string is printed.
              PS2    Secondary prompt string, by default ''> ''.
              PS3    Selection prompt string used within a select loop, by default ''#? ''.
              PS4    The value of this variable is expanded for parameter evaluation, command substitution, and arith-
                     metic  substitution and precedes each line of an execution trace.  By default, PS4 is ''+ ''.  In
                     addition when PS4 is unset, the execution trace prompt is also ''+ ''.
              SHELL  The pathname of the shell is kept in the environment.  At invocation, if  the  basename  of  this
                     variable  is rsh, rksh, or krsh, then the shell becomes restricted.  If it is pfsh or pfksh, then
                     the shell becomes a profile shell (see pfexec(1)).
              TIMEFORMAT
                     The value of this parameter is used as a format string specifying how the timing information  for
                     pipelines prefixed with the time reserved word should be displayed.  The % character introduces a
                     format sequence that is expanded to a time value or other information.  The format sequences  and
                     their meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %P        The CPU percentage, computed as (U + S) / R.

                     The  brackets  denote optional portions.  The optional p is a digit specifying the precision, the
                     number of fractional digits after a decimal point.  A value of 0 causes no decimal point or frac-
                     tion  to  be  output.  At most three places after the decimal point can be displayed; values of p
                     greater than 3 are treated as 3.  If p is not specified, the value 3 is used.

                     The optional l specifies a longer format, including hours if greater than zero, minutes, and sec-
                     onds  of  the  form  HHhMMmSS.FFs.   The  value  of  p  determines whether or not the fraction is
                     included.

                     All other characters are output without change and a trailing newline is added.   If  unset,  the
                     default  value,  $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS',  is used.  If the value is null, no timing
                     information is displayed.

              TMOUT  If set to a value greater than zero, TMOUT will be the default timeout value for the read  built-
                     in command.  The select compound command terminates after TMOUT seconds when input is from a ter-
                     minal.  Otherwise, the shell will terminate if a line is not entered within the prescribed number
                     of  seconds  while  reading from a terminal.  (Note that the shell can be compiled with a maximum
                     bound for this value which cannot be exceeded.)

              VISUAL If the value of this variable matches the pattern *[Vv][Ii]*, then the  vi  option  (see  Special
                     Command  set below) is turned on.  If the value matches the pattern *gmacs* , the gmacs option is
                     turned on.  If the value matches the pattern *macs*, then the emacs option  will  be  turned  on.
                     The value of VISUAL overrides the value of EDITOR.

       The  shell  gives  default  values  to  PATH, PS1, PS2, PS3, PS4, MAILCHECK, FCEDIT, TMOUT and IFS, while HOME,
       SHELL, ENV, and MAIL are not set at all by the shell (although HOME is set by login(1)).  On some systems  MAIL
       and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of substitutions are scanned for the field sep-
       arator characters (those found in IFS) and  split  into  distinct  fields  where  such  characters  are  found.
       Explicit  null fields ("" or ??) are retained.  Implicit null fields (those resulting from parameters that have
       no values or command substitutions with no output) are removed.

       If the braceexpand (-B) option is set then each of the fields resulting from IFS are checked  to  see  if  they
       contain  one  or  more  of  the  brace patterns {*,*}, {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} , or
       {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are letters and n1,n2,n3 are signed numbers and fmt
       is  a format specified as used by printf.  In each case, fields are created by prepending the characters before
       the { and appending the characters after the } to each of the strings generated by the characters between the {
       and }.  The resulting fields are checked to see if they have any brace patterns.

       In  the  first  form, a field is created for each string between { and ,, between , and ,, and between , and }.
       The string represented by * can contain embedded matching { and } without quoting.  Otherwise,  each  {  and  }
       with * must be quoted.

       In the seconds form, l1 and l2 must both be either upper case or both be lower case characters in the C locale.
       In this case a field is created for each character from l1 thru l2.

       In the remaining forms, a field is created for each number starting at n1 and continuing until  it  reaches  n2
       incrementing n1 by n3.  The cases where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 otherwise.
       If forms which specify %fmt any format flags, widths and precisions can be specified and fmt can end in any  of
       the  specifiers  cdiouxX.  For example, {a,z}{1..5..3%02d}{b..c}x expands to the 8 fields, a01bx, a01cx, a04bx,
       a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following splitting, each field is scanned for the characters *, ?, (, and [ unless the -f option has been set.
       If one of these characters appears, then the word is regarded as a pattern.  Each file name component that con-
       tains any pattern character is replaced with a lexicographically sorted set of names that matches  the  pattern
       from that directory.  If no file name is found that matches the pattern, then that component of the filename is
       left unchanged unless the pattern is prefixed with ~(N) in which case it is removed  as  described  below.   If
       FIGNORE  is  set,  then  each  file  name component that matches the pattern defined by the value of FIGNORE is
       ignored when generating the matching filenames.  The names .  and ..  are also ignored.  If FIGNORE is not set,
       the  character  .   at  the start of each file name component will be ignored unless the first character of the
       pattern corresponding to this component is the character .  itself.  Note,  that  for  other  uses  of  pattern
       matching the / and .  are not treated specially.

              *      Matches any string, including the null string.  When used for filename expansion, if the globstar
                     option is on, two adjacent *'s by itself will match all files and zero or  more  directories  and
                     subdirectories.  If followed by a / then only directories and subdirectories will match.
              ?      Matches any single character.
              [...]  Matches  any  one  of  the  enclosed characters.  A pair of characters separated by - matches any
                     character lexically between the pair, inclusive.  If the first character following the opening  [
                     is  a  !   or ^ then any character not enclosed is matched.  A - can be included in the character
                     set by putting it as the first or last character.
                     Within [ and ], character classes can be specified with the syntax [:class:] where class  is  one
                     of  the  following classes defined in the ANSI-C standard: (Note that word is equivalent to alnum
                     plus the character _.)
                     alnum alpha blank cntrl digit graph lower print punct space upper word xdigit
                     Within [ and ], an equivalence class can be specified with the syntax  [=c=]  which  matches  all
                     characters with the same primary collation weight (as defined by the current locale) as the char-
                     acter c.  Within [ and ], [.symbol.]  matches the collating symbol symbol.
       A pattern-list is a list of one or more patterns separated from each other with a & or |.  A &  signifies  that
       all  patterns  must  be matched whereas | requires that only one pattern be matched.  Composite patterns can be
       formed with one or more of the following sub-patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches from m to n occurrences of the given patterns.  If m is omitted, 0 will be used.  If n is
                     omitted at least m occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By  default, each pattern, or sub-pattern will match the longest string possible consistent with generating the
       longest overall match.  If more than one match is possible, the one starting closest to the  beginning  of  the
       string will be chosen.   However, for each of the above compound patterns a - can be inserted in front of the (
       to cause the shortest match to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash character \ is  treated  specially  even  when
       inside  a character class.   All ANSI-C character escapes are recognized and match the specified character.  In
       addition the following escape sequences are recognized:
              \d     Matches any character in the digit class.
              \D     Matches any character not in the digit class.
              \s     Matches any character in the space class.
              \S     Matches any character not in the space class.
              \w     Matches any character in the word class.
              \W     Matches any character not in the word class.

       A pattern of the form %(pattern-pair(s)) is a sub-pattern that can be used to match  nested  character  expres-
       sions.   Each  pattern-pair  is  a  two character sequence which cannot contain & or |.  The first pattern-pair
       specifies the starting and ending characters for the match.  Each subsequent pattern-pair represents the begin-
       ning  and ending characters of a nested group that will be skipped over when counting starting and ending char-
       acter matches.  The behavior is unspecified when the first character of a pattern-pair is alpha-numeric  except
       for the following:
              D      Causes the ending character to terminate the search for this pattern without finding a match.
              E      Causes the ending character to be interpreted as an escape character.
              L      Causes  the  ending character to be interpreted as a quote character causing all characters to be
                     ignored when looking for a match.
              Q      Causes the ending character to be interpreted as a quote character causing all  characters  other
                     than any escape character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching } is found not counting any { or } that is
       inside a double quoted string or preceded by the escape character \.  Without the {} this pattern matches any C
       language string.

       Each  sub-pattern  in  a composite pattern is numbered, starting at 1, by the location of the ( within the pat-
       tern.  The sequence \n, where n is a single digit and \n comes after the n-th. sub-pattern,  matches  the  same
       string as the sub-pattern itself.

       Finally  a  pattern can contain sub-patterns of the form ~(options:pattern-list), where either options or :pat-
       tern-list can be omitted.  Unlike the other compound patterns, these sub-patterns are not counted in  the  num-
       bered  sub-patterns.   :pattern-list must be omitted for options F, G, N , and V below.  If options is present,
       it can consist of one or more of the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              E      The remainder of the pattern uses extended regular expression syntax like the egrep(1) command.
              F      The remainder of the pattern uses fgrep(1) expression syntax.
              G      The remainder of the pattern uses basic regular expression syntax like the grep(1) command.
              K      The remainder of the pattern uses shell pattern syntax.  This is the default.
              N      This is ignored.  However, when it is the first letter and is used with file name generation, and
                     no matches occur, the file pattern expands to the empty string.
              X      The  remainder of the pattern uses augmented regular expression syntax like the xgrep(1) command.
              P      The remainder of the pattern uses perl(1)  regular  expression  syntax.   Not  all  perl  regular
                     expression syntax is currently implemented.
              V      The remainder of the pattern uses System V regular expression syntax.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
              l      Left anchor the pattern.  This is the default for K style patterns.
              r      Right anchor the pattern.  This is the default for K style patterns.
       If  both  options  and  :pattern-list  are specified, then the options apply only to  pattern-list.  Otherwise,
       these options remain in effect until they are disabled by a subsequent ~(...) or at the end of the  sub-pattern
       containing ~(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a special meaning to the shell and causes
       termination of a word unless quoted.  A character may be quoted (i.e., made to stand for itself)  by  preceding
       it with a \.  The pair \new-line is removed.  All characters enclosed between a pair of single quote marks (??)
       that is not preceded by a $ are quoted.  A single quote cannot appear  within  the  single  quotes.   A  single
       quoted string preceded by an unquoted $ is processed as an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside  double  quote marks (""), parameter and command substitution occur and \ quotes the characters \, `, ",
       and $.  A $ in front of a double quoted string will be ignored in the "C" or "POSIX" locale, and may cause  the
       string  to  be  replaced by a locale specific string otherwise.  The meaning of $* and $@ is identical when not
       quoted or when used as a variable assignment value or as a file name.  However, when used as  a  command  argu-
       ment,  "$*"  is  equivalent to "$1d$2d...", where d is the first character of the IFS variable, whereas "$@" is
       equivalent to "$1" "$2" ....  Inside grave quote marks (``), \ quotes the characters \, `, and $.  If the grave
       quotes occur within double quotes, then \ also quotes the character ".

       The  special meaning of reserved words or aliases can be removed by quoting any character of the reserved word.
       The recognition of function names or built-in command names listed below cannot be altered by quoting them.

   Arithmetic Evaluation.
       The shell performs arithmetic evaluation for arithmetic substitution, to evaluate  an  arithmetic  command,  to
       evaluate an indexed array subscript, and to evaluate arguments to the built-in commands shift and let.  Evalua-
       tions are performed using double precision floating point arithmetic or long double  precision  floating  point
       for  systems  that  provide  this  data  type.  Floating point constants follow the ANSI-C programming language
       floating point conventions.  The floating point constants Nan and Inf can be use to represent  "not  a  number"
       and  infinity  respectively.  Integer constants follow the ANSI-C programming language integer constant conven-
       tions although only single byte character constants are recognized and character casts are not recognized.   In
       addition constants can be of the form [base#]n where base is a decimal number between two and sixty-four repre-
       senting the arithmetic base and n is a number in that base.  The digits above 9 are represented  by  the  lower
       case  letters,  the  upper  case letters, @, and _ respectively.  For bases less than or equal to 36, upper and
       lower case characters can be used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associativity of expression as the  C  language.
       All the C language operators that apply to floating point quantities can be used.  In addition, the operator **
       can be used for exponentiation.  It has higher precedence than multiplication  and  is  left  associative.   In
       addition,  when the value of an arithmetic variable or sub-expression can be represented as a long integer, all
       C language integer arithmetic operations can be performed.  Variables can  be  referenced  by  name  within  an
       arithmetic  expression  without using the parameter expansion syntax.  When a variable is referenced, its value
       is evaluated as an arithmetic expression.

       Any of the following math library functions that are in the C math library can be  used  within  an  arithmetic
       expression:

       abs  acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos cosh erf erfc exp exp2 expm1 fabs fpclassify
       fdim finite floor fma fmax fmin fmod hypot ilogb int isfinite  sinf  isnan  isnormal  issubnormal  issubordered
       iszero  j0 j1 jn lgamma log log10 log2 logb nearbyint nextafter nexttoward pow remainder rint round scanb sign-
       bit sin sinh sqrt tan tanh tgamma trunc y0 y1 yn In addition, arithmetic functions can be define as shell func-
       tions with a variant of the function name syntax,

       function .sh.math.name ident ... { list ;}
              where  name  is the function name used in the arithmetic expression and each identifier, ident is a name
              reference to the long double precision floating point argument.  The value of .sh.value when  the  func-
              tion returns is the value of this function.  User defined functions can take up to 3 arguments and over-
              ride C math library functions.

       An internal representation of a variable as a double precision floating point can be specified with the -E [n],
       -F  [n],  or  -X [n] option of the typeset special built-in command.  The -E option causes the expansion of the
       value to be represented using scientific notation when it is expanded.  The optional option argument n  defines
       the  number of significant figures.  The -F option causes the expansion to be represented as a floating decimal
       number when it is expanded.  The -X option cause the expansion to be represented using the %a format defined by
       ISO  C-99.   The  optional option argument n defines the number of places after the decimal (or radix) point in
       this case.

       An internal integer representation of a variable can be specified with the -i [n] option of the typeset special
       built-in  command.   The  optional option argument n specifies an arithmetic base to be used when expanding the
       variable.  If you do not specify an arithmetic base, base 10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a variable with the -E,  -F,  -X,  or  -i
       attribute.  Assigning a floating point number to a variable whose type is an integer causes the fractional part
       to be truncated.


   Prompting.
       When used interactively, the shell prompts with the value of PS1 after expanding it  for  parameter  expansion,
       command  substitution,  and  arithmetic substitution, before reading a command.  In addition, each single !  in
       the prompt is replaced by the command number.  A !!  is required to place !  in the prompt.  If at any  time  a
       new-line is typed and further input is needed to complete a command, then the secondary prompt (i.e., the value
       of PS2) is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command to  test  attributes  of  files  and  to  compare
       strings.   Field  splitting  and  file  name generation are not performed on the words between [[ and ]].  Each
       expression can be constructed from one or more of the following unary or binary expressions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o ?option
              True, if option named option is a valid option name.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True, if file descriptor number fildes is open and associated with a terminal device.
       -u file
              True, if file exists and it has its setuid bit set.
       -v name
              True, if variable name is a valid variable name and is set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True, if file exists and is executable by current process.  If file exists and is a directory, then true
              if the current process has permission to search in the directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True, if file exists and the modification time is greater than the last access time.
       -O file
              True, if file exists and is owned by the effective user id of this process.
       -G file
              True, if file exists and its group matches the effective group id of this process.
       -R name
              True if variable name is a name reference.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True,  if  string  matches  pattern.   Any  part of pattern can be quoted to cause it to be matched as a
              string.  With a successful match to a pattern, the .sh.match array variable will contain the  match  and
              sub-pattern matches.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True,  if  string does not match pattern.  When the string matches the pattern the .sh.match array vari-
              able will contain the match and sub-pattern matches.
       string =~ ere
              True if string matches the pattern ~(E)ere where ere is an extended regular expression.
       string1 < string2
              True, if string1 comes before string2 based on ASCII value of their characters.
       string1 > string2
              True, if string1 comes after string2 based on ASCII value of their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In each of the above expressions, if file is of the form /dev/fd/n, where n is an integer,  then  the  test  is
       applied to the open file whose descriptor number is n.

       A  compound  expression  can  be  constructed  from  these  primitives by using any of the following, listed in
       decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1 || expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before a command is executed, its input and output may be redirected using a special  notation  interpreted  by
       the  shell.   The  following may appear anywhere in a simple-command or may precede or follow a command and are
       not passed on to the invoked command.  Command substitution, parameter expansion, and  arithmetic  substitution
       occur  before  word  or  digit is used except as noted below.  File name generation occurs only if the shell is
       interactive and the pattern matches a single file.  Field splitting is not performed.

       In each of the following redirections, if file is  of  the  form  /dev/sctp/host/port,  /dev/tcp/host/port,  or
       /dev/udp/host/port, where host is a hostname or host address, and port is a service given by name or an integer
       port number, then the redirection attempts to make a tcp, sctp or udp connection to the corresponding socket.

       No intervening space is allowed between the characters of redirection operators.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use file word as standard output (file descriptor 1).  If the file does not exist then it is cre-
                     ated.  If the file exists, and the noclobber option is on, this causes an error; otherwise, it is
                     truncated to zero length.

       >|word        Same as >, except that it overrides the noclobber option.

       >;word        Write output to a temporary file.  If the command completes successfully rename it to word,  oth-
                     erwise, delete the temporary file.  >;word cannot be used with the exec(2).  built-in.

       >>word        Use  file  word  as standard output.  If the file exists, then output is appended to it (by first
                     seeking to the end-of-file); otherwise, the file is created.

       <>word        Open file word for reading and writing as standard output.

       <>;word       The same as <>word except that if the command completes successfully, word is  truncated  to  the
                     offset at command completion.  <>;word cannot be used with the exec(2).  built-in.

       <<[-]word     The shell input is read up to a line that is the same as word after any quoting has been removed,
                     or to an end-of-file.  No parameter substitution, command substitution,  arithmetic  substitution
                     or  file  name  generation is performed on word.  The resulting document, called a here-document,
                     becomes the standard input.  If any character of word is quoted, then no interpretation is placed
                     upon  the  characters  of the document; otherwise, parameter expansion, command substitution, and
                     arithmetic substitution occur, \new-line is ignored, and \ must be used to quote  the  characters
                     \, $, `.  If - is appended to <<, then all leading tabs are stripped from word and from the docu-
                     ment.  If # is appended to <<, then leading spaces and tabs will be stripped off the  first  line
                     of the document and up to an equivalent indentation will be stripped from the remaining lines and
                     from word.  A tab stop is assumed to occur at every 8 columns for the purposes of determining the
                     indentation.

       <<<word       A  short  form of here document in which word becomes the contents of the here-document after any
                     parameter expansion, command substitution, and arithmetic substitution occur.

       <&digit       The standard input is duplicated from file descriptor digit  (see  dup(2)).   Similarly  for  the
                     standard output using >&digit.

       <&digit-      The file descriptor given by digit is moved to standard input.  Similarly for the standard output
                     using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       <#((expr))    Evaluate arithmetic expression expr and position file descriptor 0 to the resulting  value  bytes
                     from the start of the file.  The variables CUR and EOF evaluate to the current offset and end-of-
                     file offset respectively when evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks forward to the beginning of the next line containing pattern.

       <##pattern    The same as <# except that the portion of the file that is skipped is copied to standard  output.

       If one of the above is preceded by a digit, with no intervening space, then the file descriptor number referred
       to is that specified by the digit (instead of the default 0 or 1).  If one of the above, other than >&- and the
       ># and <# forms, is preceded by {varname} with no intervening space, then a file descriptor number > 10 will be
       selected by the shell and stored in the variable varname.  If >&- or the any of the ># and <# forms is preceded
       by {varname} the value of varname defines the file descriptor to close or position.  For example:

              ... 2>&1

       means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and

              exec {n}<file

       means open file named file for reading and store the file descriptor number in variable n.

       The order in which redirections are specified is significant.  The shell evaluates each redirection in terms of
       the (file descriptor, file) association at the time of evaluation.  For example:

              ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates file descriptor 2 with the file associ-
       ated with file descriptor 1 (i.e.  fname).  If the order of redirections were reversed, file descriptor 2 would
       be associated with the terminal (assuming file descriptor 1 had been) and then file descriptor 1 would be asso-
       ciated with file fname.

       If a command is followed by & and job control is not active, then the default standard input for the command is
       the empty file /dev/null.  Otherwise, the environment for the execution of a command contains the file descrip-
       tors of the invoking shell as modified by input/output specifications.

   Environment.
       The  environment  (see  environ(7))  is a list of name-value pairs that is passed to an executed program in the
       same way as a normal argument list.  The names must be identifiers and the values are character  strings.   The
       shell  interacts with the environment in several ways.  On invocation, the shell scans the environment and cre-
       ates a variable for each name found, giving it the corresponding value and attributes and  marking  it  export.
       Executed  commands  inherit the environment.  If the user modifies the values of these variables or creates new
       ones, using the export or typeset -x commands, they become part of the environment.  The  environment  seen  by
       any  executed  command is thus composed of any name-value pairs originally inherited by the shell, whose values
       may be modified by the current shell, plus any additions which must be noted in export or typeset -x  commands.

       The  environment  for any simple-command or function may be augmented by prefixing it with one or more variable
       assignments.  A variable assignment argument is a word of the form identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are equivalent (as far as the above execution of cmd is concerned except for special built-in  commands  listed
       below - those that are preceded with a dagger).

       If the obsolete -k option is set, all variable assignment arguments are placed in the environment, even if they
       occur after the command name.  The following first prints a=b c and then c:

              echo a=b c
              set -k
              echo a=b c
       This feature is intended for use with scripts written for early versions of  the  shell  and  its  use  in  new
       scripts is strongly discouraged.  It is likely to disappear someday.

   Functions.
       For historical reasons, there are two ways to define functions, the name() syntax and the function name syntax,
       described in the Commands section above.  Shell functions are read in and stored internally.  Alias  names  are
       resolved  when  the  function is read.  Functions are executed like commands with the arguments passed as posi-
       tional parameters.  (See Execution below.)

       Functions defined by the function name syntax and called by name execute in the same process as the caller  and
       share  all  files and present working directory with the caller.  Traps caught by the caller are reset to their
       default action inside the function.  A trap condition that is not caught or ignored by the function causes  the
       function to terminate and the condition to be passed on to the caller.  A trap on EXIT set inside a function is
       executed in the environment of the caller after the  function  completes.   Ordinarily,  variables  are  shared
       between  the  calling  program  and  the function.  However, the typeset special built-in command used within a
       function defines local variables whose scope includes the current function.  They can be  passed  to  functions
       that  they  call  in  the variable assignment list that precedes the call or as arguments passed as name refer-
       ences.  Errors within functions return control to the caller.

       Functions defined with the name() syntax and functions defined with the function name syntax that  are  invoked
       with  the  .   special built-in are executed in the caller's environment and share all variables and traps with
       the caller.  Errors within these function executions cause the script that contains them to abort.

       The special built-in command return is used to return from function calls.

       Function names can be listed with the -f or +f option of the typeset special built-in  command.   The  text  of
       functions,  when  available, will also be listed with -f.  Functions can be undefined with the -f option of the
       unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.  Functions  that  need  to  be  defined
       across  separate invocations of the shell should be placed in a directory and the FPATH variable should contain
       the name of this directory.  They may also be specified in the ENV file.

   Discipline Functions.
       Each variable can have zero or more discipline functions associated with it.  The shell  initially  understands
       the  discipline  names  get,  set, append, and unset but can be added when defining new types.  On most systems
       others can be added at run time via the C programming interface extension  provided  by  the  builtin  built-in
       utility.   If the get discipline is defined for a variable, it is invoked whenever the given variable is refer-
       enced.  If the variable .sh.value is assigned a value inside the discipline function, the  referenced  variable
       will  evaluate  to this value instead.  If the set discipline is defined for a variable, it is invoked whenever
       the given variable is assigned a value.  If the append discipline is defined for  a  variable,  it  is  invoked
       whenever  a value is appended to the given variable.  The variable .sh.value is given the value of the variable
       before invoking the discipline, and the variable will be assigned the value of .sh.value after  the  discipline
       completes.  If .sh.value is unset inside the discipline, then that value is unchanged.  If the unset discipline
       is defined for a variable, it is invoked whenever the given variable is unset.  The variable will not be  unset
       unless it is unset explicitly from within this discipline function.

       The  variable  .sh.name contains the name of the variable for which the discipline function is called, .sh.sub-
       script is the subscript of the variable, and .sh.value will contain the value being  assigned  inside  the  set
       discipline  function.   The  variable _ is a reference to the variable including the subscript if any.  For the
       set discipline, changing  .sh.value  will  change  the  value  that  gets  assigned.   Finally,  the  expansion
       ${var.name}, when name is the name of a discipline, and there is no variable of this name, is equivalent to the
       command substitution ${ var.name;}.


   Name Spaces.
       Commands and functions that are executed as part of the list of a namespace command that  modify  variables  or
       create new ones, create a new variable whose name is the name of the name space as given by identifier preceded
       by ..  When a variable whose name is name is referenced, it is first searched for using .identifier.name.  Sim-
       ilarly, a function defined by a command in the namespace list is created using the name space name  preceded by
       a ..

       When  the list of a namespace command contains a namespace command, the names of variables and  functions  that
       are created consist of the variable or function name preceded by the list of identifiers each preceded by ..

       Outside  of  a name space, a variable or function created inside a name space can be referenced by preceding it
       with the name space name.

       By default, variables staring with .sh are in the sh name space.


   Type Variables.
       Typed variables provide a way to create data structure and objects.  A type can be defined either by  a  shared
       library,  by  the  enum built-in command described below, or by using the new -T option of the typeset built-in
       command.  With the -T option of typeset, the type name, specified as an option argument to -T, is  set  with  a
       compound  variable assignment that defines the type.  Function definitions can appear inside the compound vari-
       able assignment and these become discipline functions for this type and can be invoked  or  redefined  by  each
       instance  of  the type.  The function name create is treated specially.  It is invoked for each instance of the
       type that is created but is not inherited and cannot be redefined for each instance.

       When a type is defined a special built-in command of that name is added.  These built-ins are declaration  com-
       mands  and follow the same expansion rules as all the special built-in commands defined below that are preceded
       by ++.  These commands can subsequently be used inside further type definitions.  The man page for  these  com-
       mands  can  be  generated by using the --man option or any of the other -- options described with getopts.  The
       -r, -a, -A, -h, and -S options of typeset are permitted with each of these new built-ins.

       An instance of a type is created by invoking the type name followed  by  one  or  more  instance  names.   Each
       instance  of the type is initialized with a copy of the sub-variables except for sub-variables that are defined
       with the -S option.  Variables defined with the -S are shared by all instances of the type.  Each instance  can
       change  the  value  of any sub-variable and can also define new discipline functions of the same names as those
       defined by the type definition as well as any standard discipline names.  No additional  sub-variables  can  be
       defined for any instance.

       When  defining  a  type, if the value of a sub-variable is not set and the -r attribute is specified, it causes
       the sub-variable to be a required sub-variable.  Whenever an instance of a type is created, all  required  sub-
       variables must be specified.  These sub-variables become readonly in each instance.

       When  unset  is  invoked  on a sub-variable within a type, and the -r attribute has not been specified for this
       field, the value is reset to the default value associative with the type.  Invoking unset on  a  type  instance
       not contained within another type deletes all sub-variables and the variable itself.

       A  type definition can be derived from another type definition by defining the first sub-variable name as _ and
       defining its type as the base type.  Any remaining definitions will be additions and modifications  that  apply
       to  the new type.  If the new type name is the same is that of the base type, the type will be replaced and the
       original type will no longer be accessible.

       The typeset command with the -T and no option argument or operands will write all the type definitions to stan-
       dard output in a form that that can be read in to create all they types.

   Jobs.
       If  the  monitor  option  of  the  set  command  is  turned on, an interactive shell associates a job with each
       pipeline.  It keeps a table of current jobs, printed by the jobs command, and assigns them small  integer  num-
       bers.  When a job is started asynchronously with &, the shell prints a line which looks like:

            [1] 1234

       indicating  that  the  job  which  was started asynchronously was job number 1 and had one (top-level) process,
       whose process id was 1234.

       This paragraph and the next require features that are not in all versions of UNIX and may not  apply.   If  you
       are running a job and wish to do something else you may hit the key ^Z (control-Z) which sends a STOP signal to
       the current job.  The shell will then normally indicate that the job has  been  'Stopped',  and  print  another
       prompt.   You  can  then manipulate the state of this job, putting it in the background with the bg command, or
       run some other commands and then eventually bring the job back into the foreground with the foreground  command
       fg.   A  ^Z  takes effect immediately and is like an interrupt in that pending output and unread input are dis-
       carded when it is typed.

       A job being run in the background will stop if it tries to read from the terminal.  Background  jobs  are  nor-
       mally  allowed  to produce output, but this can be disabled by giving the command stty tostop.  If you set this
       tty option, then background jobs will stop when they try to produce output like they do when they try  to  read
       input.

       A job pool is a collection of jobs started with list & associated with a name.

       There  are  several ways to refer to jobs in the shell.  A job can be referred to by the process id of any pro-
       cess of the job or by one of the following:
       %number
              The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
              The job number number in the job pool named by pool.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.  In addition, unless noted otherwise, wherever a job can be specified, the name of a back-
              ground job pool can be used to represent all the jobs in that pool.

       The  shell learns immediately whenever a process changes state.  It normally informs you whenever a job becomes
       blocked so that no further progress is possible, but only just before it prints a prompt.  This is done so that
       it  does not otherwise disturb your work.  The notify option of the set command causes the shell to print these
       job change messages as soon as they occur.

       When the monitor option is on, each background job that completes triggers any trap set for CHLD.

       When you try to leave the shell while jobs  are  running  or  stopped,  you  will  be  warned  that  'You  have
       stopped(running)  jobs.'   You  may  use the jobs command to see what they are.  If you immediately try to exit
       again, the shell will not warn you a second time, and the stopped jobs will be terminated.  When a login  shell
       receives  a  HUP  signal, it sends a HUP signal to each job that has not been disowned with the disown built-in
       command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the command is followed by  &  and  the  monitor
       option  is active.  Otherwise, signals have the values inherited by the shell from its parent (but see also the
       trap built-in command below).

   Execution.
       Each time a command is read, the above substitutions are carried out.  If the command name matches one  of  the
       Special  Built-in  Commands  listed  below, it is executed within the current shell process.  Next, the command
       name is checked to see if it matches a user defined function.  If it does, the positional parameters are  saved
       and  then  reset  to the arguments of the function call.  A function is also executed in the current shell pro-
       cess.  When the function completes or issues a return, the positional parameter list is  restored.   For  func-
       tions  defined  with  the function name syntax, any trap set on EXIT within the function is executed.  The exit
       value of a function is the value of the last command executed.  If a command name is  not  a  special  built-in
       command  or a user defined function, but it is one of the built-in commands listed below, it is executed in the
       current shell process.

       The shell variables PATH followed by the variable FPATH defines the list of directories to search for the  com-
       mand  name.   Alternative  directory  names  are  separated  by a colon (:).  The default path is equal to get-
       conf PATH output.  The current directory can be specified by two or more adjacent colons, or by a colon at  the
       beginning or end of the path list.  If the command name contains a /, then the search path is not used.  Other-
       wise, each directory in the list of directories defined by PATH and FPATH is checked in order.  If  the  direc-
       tory  being  searched  is contained in FPATH and contains a file whose name matches the command being searched,
       then this file is loaded into the current shell environment as if it were the argument to the . command  except
       that only preset aliases are expanded, and a function of the given name is executed as described above.

       If  this  directory is not in FPATH the shell first determines whether there is a built-in version of a command
       corresponding to a given pathname and if so it is invoked in the current process.  If no built-in is found, the
       shell  checks  for  a file named .paths in this directory.  If found and there is a line of the form FPATH=path
       where path names an existing directory then that directory is searched  after  immediately  after  the  current
       directory as if it were found in the FPATH variable.  If path does not begin with /, it is checked for relative
       to the directory being searched.

       The .paths file is then checked  for a line of the form PLUGIN_LIB=libname [ : libname ] ...  .   Each  library
       named  by  libname  will  be  searched for as if it were an option argument to builtin -f, and if it contains a
       built-in of the specified name this will be executed instead of a command by this name.   Any  built-in  loaded
       from  a library found this way will be associated with the directory containing the .paths file so it will only
       execute if not found in an earlier directory.

       Finally, the directory will be checked for a file of the given name.  If the file has execute permission but is
       not  an  a.out file, it is assumed to be a file containing shell commands.  A separate shell is spawned to read
       it.  All non-exported variables are removed in this case.  If the shell command file doesn't have read  permis-
       sion, or if the setuid and/or setgid bits are set on the file, then the shell executes an agent whose job it is
       to set up the permissions and execute the shell with the shell command file passed down as an  open  file.   If
       the  .paths  contains  a line of the form name=value in the first or second line, then the environment variable
       name is modified by prepending the directory specified by value to the directory list.   If  value  is  not  an
       absolute  directory, then it specifies a directory relative to the directory that the executable was found.  If
       the environment variable name does not already exist it will be added to the environment list for the specified
       command.  A parenthesized command is executed in a sub-shell without removing non-exported variables.

   Command Re-entry.
       The text of the last HISTSIZE (default 512) commands entered from a terminal device is saved in a history file.
       The file $HOME/.sh_history is used if the HISTFILE variable is not set or if the file it names is not writable.
       A shell can access the commands of all interactive shells which use the same named HISTFILE.  The built-in com-
       mand hist is used to list or edit a portion of this file.  The portion of the file to be edited or  listed  can
       be selected by number or by giving the first character or characters of the command.  A single command or range
       of commands can be specified.  If you do not specify an editor program as an argument to hist then the value of
       the  variable  HISTEDIT is used.  If HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT is not
       defined, then /bin/ed is used.  The edited command(s) is printed and re-executed upon leaving the editor unless
       you  quit  without  writing.   The  -s option (and in obsolete versions, the editor name -) is used to skip the
       editing phase and to re-execute the command.  In this case a substitution parameter of the form old=new can  be
       used  to  modify the command before execution.  For example, with the preset alias r, which is aliased to ?hist
       -s?, typing 'r bad=good c' will re-execute the most recent command which starts with the  letter  c,  replacing
       the first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally,  each command line entered from a terminal device is simply typed followed by a new-line ('RETURN' or
       'LINE FEED').  If either the emacs, gmacs, or vi option is active, the user can edit the command line.   To  be
       in  either  of these edit modes set the corresponding option.  An editing option is automatically selected each
       time the VISUAL or EDITOR variable is assigned a value ending in either of these option names.

       The editing features require that the user's terminal accept 'RETURN' as carriage return without line feed  and
       that a space (' ') must overwrite the current character on the screen.

       Unless  the  multiline  option is on, the editing modes implement a concept where the user is looking through a
       window at the current line.  The window width is the value of COLUMNS if it is defined, otherwise 80.   If  the
       window  width  is  too  small  to display the prompt and leave at least 8 columns to enter input, the prompt is
       truncated from the left.  If the line is longer than the window width minus two, a mark is displayed at the end
       of  the  window  to  notify the user.  As the cursor moves and reaches the window boundaries the window will be
       centered about the cursor.  The mark is a > (<, *) if the line extends on the right (left, both) side(s) of the
       window.

       The  search  commands in each edit mode provide access to the history file.  Only strings are matched, not pat-
       terns, although a leading ^ in the string restricts the match to begin at the first character in the line.

       Each of the edit modes has an operation to list the files or commands that  match  a  partially  entered  word.
       When  applied  to  the  first  word on the line, or the first word after a ;, |, &, or (, and the word does not
       begin with ~ or contain a /, the list of aliases, functions, and executable commands defined by the PATH  vari-
       able that could match the partial word is displayed.  Otherwise, the list of files that match the given word is
       displayed.  If the partially entered word does not contain any file  expansion  characters,  a  *  is  appended
       before  generating  these lists.  After displaying the generated list, the input line is redrawn.  These opera-
       tions are called command name listing and file name listing, respectively.  There  are  additional  operations,
       referred to as command name completion and file name completion, which compute the list of matching commands or
       files, but instead of printing the list, replace the current word with a complete or partial match.   For  file
       name  completion, if the match is unique, a / is appended if the file is a directory and a space is appended if
       the file is not a directory.  Otherwise, the longest common prefix for all  the  matching  files  replaces  the
       word.   For  command  name completion, only the portion of the file names after the last / are used to find the
       longest command prefix.  If only a single name matches this prefix, then the word is replaced with the  command
       name followed by a space.  When using a tab for completion that does not yield a unique match, a subsequent tab
       will provide a numbered list of matching alternatives.  A specific selection can be made by entering the selec-
       tion number followed by a tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys as they are typed and change the characters that are actually seen
       by the shell.  This trap is executed after each character (or sequence of characters when the  first  character
       is  ESC) is entered while reading from a terminal.  The variable .sh.edchar contains the character or character
       sequence which generated the trap.  Changing the value of .sh.edchar in the trap action  causes  the  shell  to
       behave as if the new value were entered from the keyboard rather than the original value.

       The  variable .sh.edcol is set to the input column number of the cursor at the time of the input.  The variable
       .sh.edmode is set to ESC when in vi insert mode (see below) and is null otherwise.  By  prepending  ${.sh.edit-
       mode}  to a value assigned to .sh.edchar it will cause the shell to change to control mode if it is not already
       in this mode.

       This trap is not invoked for characters entered as arguments to editing directives, or while reading input  for
       a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The only difference between these two modes
       is the way they handle ^T.  To edit, the user moves the cursor to the point needing correction and then inserts
       or deletes characters or words as needed.  All the editing commands are control characters or escape sequences.
       The notation for control characters is caret (^) followed by the character.  For example, ^F  is  the  notation
       for control F.  This is entered by depressing 'f' while holding down the 'CTRL' (control) key.  The 'SHIFT' key
       is not depressed.  (The notation ^?  indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a character.  For  example,  M-f  (pronounced  Meta  f)  is
       entered  by depressing ESC (ascii 033) followed by 'f'.  (M-F would be the notation for ESC followed by 'SHIFT'
       (capital) 'F'.)

       All edit commands operate from any place on the line (not just at the beginning).  Neither the 'RETURN' nor the
       'LINE FEED' key is entered after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move  cursor forward one word.  (The emacs editor's idea of a word is a string of characters consist-
                 ing of only letters, digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User defined erase character as defined by the stty(1) command, usually ^H or #.)   Delete  previous
                 character.
       lnext     (User  defined  literal  next  character  as  defined  by the stty(1) command, or ^V if not defined.)
                 Removes the next character's editing features (if any).
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL) Delete previous word (if your interrupt character is ^?  (DEL, the default) then this com-
                 mand will not work).
       ^T        Transpose  current character with previous character and advance the cursor in emacs mode.  Transpose
                 two previous characters in gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete from the cursor to the end of the line.  If preceded by a numerical parameter whose  value  is
                 less than the current cursor position, then delete from given position up to the cursor.  If preceded
                 by a numerical parameter whose value is greater than the current cursor position,  then  delete  from
                 cursor up to given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User  defined kill character as defined by the stty command, usually ^G or @.)  Kill the entire cur-
                 rent line.  If two kill characters are entered in succession, all kill characters from then on  cause
                 a line feed (useful when using paper terminals).
       ^Y        Restore last item removed from line. (Yank item back to the line.)
       ^L        Line feed and print current line.
       M-^L      Clear the screen.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file  character, normally ^D, is processed as an End-of-file only if the current line is null.
       ^P        Fetch previous command.  Each time ^P is entered the previous  command  back  in  time  is  accessed.
                 Moves back one line when not on the first line of a multi-line command.
       M-[A      If  the  cursor  is at the end of the line, it is equivalent to ^R with string set to the contents of
                 the current line.  Otherwise, it is equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is entered the next command line forward in time is  accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse  search  history  for  a  previous command line containing string.  If a parameter of zero is
                 given, the search is forward.  String is terminated by a 'RETURN' or 'NEW LINE'.  If string  is  pre-
                 ceded  by  a ^, the matched line must begin with string.  If string is omitted, then the next command
                 line containing the most recent string is accessed.  In this case a parameter of  zero  reverses  the
                 direction of the search.
       ^O        Operate  - Execute the current line and fetch the next line relative to current line from the history
                 file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as a parameter to the next command.  The com-
                 mands  that accept a parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-., M-^], M-_, M-=, M-
                 b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key - Your alias list is searched for an alias by the name _letter and if an alias of this  name
                 is  defined,  its value will be inserted on the input queue.  The letter must not be one of the above
                 meta-functions.
       M-[letter Soft-key - Your alias list is searched for an alias by the name __letter and if an alias of this name
                 is defined, its value will be inserted on the input queue.  This can be used to program function keys
                 on many terminals.
       M-.       The last word of the previous command is inserted on the line.  If preceded by a  numeric  parameter,
                 the value of this parameter determines which word to insert rather than the last word.
       M-_       Same as M-..
       M-*       Attempt  file name generation on the current word.  An asterisk is appended if the word doesn't match
                 any file or contain any special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I tab    Attempts command or file name completion as described above.  If a partial completion occurs, repeat-
                 ing  this  will behave as if M-= were entered.  If no match is found or entered after space, a tab is
                 inserted.
       M-=       If not preceded by a numeric parameter, it generates the list of matching commands or file  names  as
                 described  above.   Otherwise, the word under the cursor is replaced by the item corresponding to the
                 value of the numeric parameter from the most recently generated command or file list.  If the  cursor
                 is not on a word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user's erase, kill and interrupt (normally ^?)  char-
                 acters may be entered in a command line or in a search string if preceded by a \.  The \ removes  the
                 next character's editing features (if any).
       M-^V      Display version of the shell.
       M-#       If the line does not begin with a #, a # is inserted at the beginning of the line and after each new-
                 line, and the line is entered.  This causes a comment to be inserted in the  history  file.   If  the
                 line begins with a #, the # is deleted and one # after each new-line is also deleted.

   Vi Editing Mode.
       There  are two typing modes.  Initially, when you enter a command you are in the input mode.  To edit, the user
       enters control mode by typing ESC (033) and moves the cursor to the point needing correction and  then  inserts
       or  deletes  characters or words as needed.  Most control commands accept an optional repeat count prior to the
       command.

       When in vi mode on most systems, canonical processing is initially enabled and the command will be echoed again
       if the speed is 1200 baud or greater and it contains any control characters or less than one second has elapsed
       since the prompt was printed.  The ESC character terminates canonical processing for the remainder of the  com-
       mand  and  the  user  can then modify the command line.  This scheme has the advantages of canonical processing
       with the type-ahead echoing of raw mode.

       If the option viraw is also set, the terminal will always have canonical processing  disabled.   This  mode  is
       implicit  for  systems that do not support two alternate end of line delimiters, and may be helpful for certain
       terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User defined erase character as defined by the stty command, usually ^H or #.)  Delete previ-
                        ous character.
              ^W        Delete  the  previous  blank separated word.  On some systems the viraw option may be required
                        for this to work.
              eof       As the first character of the line causes the shell to terminate unless the  ignoreeof  option
                        is set.  Otherwise this character is ignored.
              lnext     (User defined literal next character as defined by the stty(1) or ^V if not defined.)  Removes
                        the next character's editing features (if any).  On some  systems  the  viraw  option  may  be
                        required for this to work.
              \         Escape the next erase or kill character.
              ^I tab    Attempts  command  or file name completion as described above and returns to input mode.  If a
                        partial completion occurs, repeating this will behave as if = were entered from control  mode.
                        If no match is found or entered after space, a tab is inserted.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor to the beginning of the next word that follows a blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]|  Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats count times, the last single character find command, f, F, t, or T.
              [count],  Reverses the last single character find command count times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves  to balancing (, ), {, }, [, or ].  If cursor is not on one of the above characters, the
                        remainder of the line is searched for the first occurrence of  one  of  the  above  characters
                        first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch previous command.  Each time k is entered the previous command back in time is accessed.
              [count]-  Equivalent to k.
              [count][A If cursor is at the end of the line it is equivalent to / with string^set to the  contents  of
                        the current line.  Otherwise, it is equivalent to k.
              [count]j  Fetch next command.  Each time j is entered the next command forward in time is accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The command number count is fetched.  The default is the least recent history command.
              /string   Search  backward  through  history for a previous command containing string.  String is termi-
                        nated by a 'RETURN' or 'NEW LINE'.  If string is preceded by a ^, the matched line must  begin
                        with string.  If string is null, the previous string will be used.
              ?string   Same as / except that search will be in the forward direction.
              n         Search for next match of the last pattern to / or ?  commands.
              N         Search for next match of the last pattern to / or ?, but in reverse direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter input mode and enter text after the current character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete  current character through the character that motion would move the cursor to and enter
                        input mode.  If motion is c, the entire line will be deleted and input mode entered.
              C         Delete the current character through the end of line and enter input mode.  Equivalent to  c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete the current character through the end of line.  Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete  current  character  through the character that motion would move to.  If motion is d ,
                        the entire line will be deleted.
              i         Enter input mode and insert text before the current character.
              I         Insert text before the beginning of the line.  Equivalent to 0i.
              [count]P  Place the previous text modification before the cursor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter input mode and replace characters on the screen with characters you type  overlay  fash-
                        ion.
              [count]rc Replace the count character(s) starting at the current cursor position with c, and advance the
                        cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]~  Invert the case of the count character(s) starting at the current cursor position and  advance
                        the cursor.
              [count]_  Causes the count word of the previous command to be appended and input mode entered.  The last
                        word is used if count is omitted.
              *         Causes an * to be appended to the current word and file  name  generation  attempted.   If  no
                        match  is  found,  it rings the bell.  Otherwise, the word is replaced by the matching pattern
                        and input mode is entered.
              \         Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank current character through character that motion would move the cursor to  and  puts  them
                        into the delete buffer.  The text and cursor are unchanged.
              yy        Yanks the entire line.
              Y         Yanks from current position to end of line.  Equivalent to y$.
              u         Undo the last text modifying command.
              U         Undo all the text modifying commands performed on the line.
              [count]v  Returns  the  command hist -e ${VISUAL:-${EDITOR:-vi}} count in the input buffer.  If count is
                        omitted, then the current line is used.
              ^L        Line feed and print current line.  Has effect only in control mode.
              ^J        (New line) Execute the current line, regardless of mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If the first character of the command is a #, then this command deletes this # and each # that
                        follows a newline.  Otherwise, sends the line after inserting a # in front of each line in the
                        command.  Useful for causing the current line to be inserted in the history as a  comment  and
                        uncommenting previously commented commands in the history file.
              [count]=  If  count  is  not  specified,  it  generates  the  list of matching commands or file names as
                        described above.  Otherwise, the word under the the cursor is replaced by the count item  from
                        the  most  recently  generated  command  or  file list.  If the cursor is not on a word, it is
                        inserted instead.
              @letter   Your alias list is searched for an alias by the name _letter and if an alias of this  name  is
                        defined, its value will be inserted on the input queue for processing.
              ^V        Display version of the shell.

   Built-in Commands.
       The  following  simple-commands  are  executed  in  the  shell process.  Input/Output redirection is permitted.
       Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when  there  is  no
       syntax  error, is zero.  Except for :, true, false, echo, newgrp, and login, all built-in commands accept -- to
       indicate end of options.  They also interpret the option --man as a request to display the man page onto  stan-
       dard  error  and  -?  as a help request which prints a usage message on standard error.  Commands that are pre-
       ceded by one or two + symbols are special built-in commands and are treated specially in the following ways:
       1.     Variable assignment lists preceding the command remain in effect when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words following a command preceded by ++ that are in the format of a variable  assignment  are  expanded
              with the same rules as a variable assignment.  This means that tilde substitution is performed after the
              = sign and field splitting and file name generation are not performed.   These  are  called  declaration
              built-ins.

       + : [ arg ... ]
              The command only expands parameters.

       + . name [ arg ... ]
              If  name  is a function defined with the function name reserved word syntax, the function is executed in
              the current environment (as if it had been defined with the name() syntax.)  Otherwise if name refers to
              a file, the file is read in its entirety and the commands are executed in the current shell environment.
              The search path specified by PATH is used to find the directory containing the file.  If  any  arguments
              arg  are  given,  they become the positional parameters while processing the .  command and the original
              positional parameters are restored upon completion.  Otherwise the positional parameters are  unchanged.
              The exit status is the exit status of the last command executed.

       ++ alias [ -ptx ]  [ name[ =value  ] ] ...
              alias  with  no  arguments prints the list of aliases in the form name=value on standard output.  The -p
              option causes the word alias to be inserted before each one.  When one or more arguments are  given,  an
              alias  is defined for each name whose value is given.  A trailing space in value causes the next word to
              be checked for alias substitution.  The obsolete -t option is used to set and list tracked aliases.  The
              value  of a tracked alias is the full pathname corresponding to the given name.  The value becomes unde-
              fined when the value of PATH is reset but the alias remains tracked.  Without the -t  option,  for  each
              name  in the argument list for which no value is given, the name and value of the alias is printed.  The
              obsolete -x option has no effect.  The exit status is non-zero if a name is given, but no value, and  no
              alias has been defined for the name.

       bg [ job... ]
              This  command is only on systems that support job control.  Puts each specified job into the background.
              The current job is put in the background if job is not specified.  See Jobs for  a  description  of  the
              format of job.

       + break [ n ]
              Exit from the enclosing for, while, until, or select loop, if any.  If n is specified, then break n lev-
              els.

       builtin [ -ds ] [ -f file ] [ name ... ]
              If name is not specified, and no -f option is specified, the built-ins are printed on  standard  output.
              The  -s  option  prints  only the special built-ins.  Otherwise, each name represents the pathname whose
              basename is the name of the built-in.  The entry point function name is determined by prepending  b_  to
              the built-in name.  A built-in specified by a pathname will only be executed when that pathname would be
              found during the path search.  Built-ins found in libraries loaded via the .paths file will be associate
              with the pathname of the directory containing the .paths file.

       The ISO C/C++ prototype is b_mycommand(int argc, char *argv[], void *context) for the builtin command mycommand
       where argv is array an of argc elements and context is an optional pointer to a Shell_t structure as  described
       in <ast/shell.h>.
       Special built-ins cannot be bound to a pathname or deleted.  The -d option deletes each of the given built-ins.
       On systems that support dynamic loading, the -f option names a shared library containing the  code  for  built-
       ins.   The  shared library prefix and/or suffix, which depend on the system, can be omitted.  Once a library is
       loaded, its symbols become available for subsequent invocations of builtin.  Multiple libraries can  be  speci-
       fied  with  separate  invocations of the builtin command.  Libraries are searched in the reverse order in which
       they are specified.  When a library is loaded, it looks for a function in the library whose name is  lib_init()
       and invokes this function with an argument of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This  command can be in either of two forms.  In the first form it changes the current directory to arg.
              If arg is - the directory is changed to the previous directory.  The shell variable HOME is the  default
              arg.   The  variable  PWD is set to the current directory.  The shell variable CDPATH defines the search
              path for the directory containing arg.  Alternative directory names are separated by a colon  (:).   The
              default path is <null> (specifying the current directory).  Note that the current directory is specified
              by a null path name, which can appear immediately after the equal sign or between the  colon  delimiters
              anywhere  else  in  the path list.  If arg begins with a / then the search path is not used.  Otherwise,
              each directory in the path is searched for arg.
              The second form of cd substitutes the string new for the string old in the current directory name,  PWD,
              and tries to change to this new directory.
              By  default, symbolic link names are treated literally when finding the directory name.  This is equiva-
              lent to the -L option.  The -P option causes symbolic links to be resolved when determining  the  direc-
              tory.  The last instance of -L or -P on the command line determines which method is used.
              The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
              Without  the  -v  or  -V  options, command executes name with the arguments given by arg.  The -p option
              causes a default path to be searched rather than the one defined by the value of PATH.   Functions  will
              not  be  searched for when finding name.  In addition, if name refers to a special built-in, none of the
              special properties associated with the leading daggers will be honored.  (For  example,  the  predefined
              alias  redirect=?command exec? prevents a script from terminating when an invalid redirection is given.)
              With the -x option, if command execution would result in a failure because there are too many arguments,
              errno  E2BIG,  the  shell will invoke command name multiple times with a subset of the arguments on each
              invocation.  Arguments that occur prior to the first word that expands to multiple arguments  and  after
              the  last  word  that  expands to multiple arguments will be passed on each invocation.  The exit status
              will be the maximum invocation exit status.  With the -v option, command is equivalent to  the  built-in
              whence command described below.  The -V option causes command to act like whence -v.

       + continue [ n ]
              Resume  the  next iteration of the enclosing for, while, until, or select loop.  If n is specified, then
              resume at the n-th enclosing loop.

       disown [ job... ]
              Causes the shell not to send a HUP signal to each given job, or all active jobs if job is omitted,  when
              a login shell terminates.

       echo [ arg ... ]
              When the first arg does not begin with a -, and none of the arguments contain a \, then echo prints each
              of its arguments separated by a space and terminated by a new-line.  Otherwise, the behavior of echo  is
              system dependent and print or printf described below should be used.  See echo(1) for usage and descrip-
              tion.

       ++ enum [ -i  ] type[=(value ...) ]
              Creates a declaration command named type that is an integer type that allows one of the specified values
              as  enumeration  names.  If =(value ...) is omitted, then type must be an indexed array variable with at
              least two elements and the values are taken from this array variable.  If -i is specified the values are
              case insensitive.

       + eval [ arg ... ]
              The arguments are read as input to the shell and the resulting command(s) executed.

       + exec [ -c ] [ -a name ] [ arg ... ]
              If  arg is given, the command specified by the arguments is executed in place of this shell without cre-
              ating a new process.  The -c option causes the  environment  to  be  cleared  before  applying  variable
              assignments  associated  with the exec invocation.  The -a option causes name rather than the first arg,
              to become argv[0] for the new process.  Input/output arguments may appear and affect  the  current  pro-
              cess.   If  arg  is not given, the effect of this command is to modify file descriptors as prescribed by
              the input/output redirection list.  In this case, any file descriptor numbers greater than  2  that  are
              opened with this mechanism are closed when invoking another program.

       + exit [ n ]
              Causes the shell to exit with the exit status specified by n.  The value will be the least significant 8
              bits of the specified status.  If n is omitted, then the exit status is that of the  last  command  exe-
              cuted.   An  end-of-file  will  also  cause the shell to exit except for a shell which has the ignoreeof
              option (see set below) turned on.

       ++ export [ -p ] [ name[=value] ] ...
              If name is not given, the names and values of each variable with the export attribute are  printed  with
              the  values quoted in a manner that allows them to be re-input.  The export command is the same as type-
              set -x except that if you use export within a function, no local variable is  created.   The  -p  option
              causes  the word export to be inserted before each one.  Otherwise, the given names are marked for auto-
              matic export to the environment of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This command is only on systems that support job control.  Each job specified is brought  to  the  fore-
              ground  and  waited  for  in  the specified order.  Otherwise, the current job is brought into the fore-
              ground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
              Prints the current value of the configuration parameter given by name.  The configuration parameters are
              defined  by  the  IEEE  POSIX 1003.1 and IEEE POSIX 1003.2 standards.  (See pathconf(2) and sysconf(2).)
              The pathname argument is required for parameters whose value depends on the location in the file system.
              If  no arguments are given, getconf prints the names and values of the current configuration parameters.
              The pathname / is used for each of the parameters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks arg for legal options.  If arg is omitted, the positional parameters are used.  An  option  argu-
              ment  begins  with a + or a -.  An option not beginning with + or - or the argument -- ends the options.
              Options beginning with + are only recognized when optstring begins with a  +.   optstring  contains  the
              letters  that  getopts  recognizes.   If a letter is followed by a :, that option is expected to have an
              argument.  The options can be separated from the argument by blanks.  The option -?  causes  getopts  to
              generate  a usage message on standard error.  The -a argument can be used to specify the name to use for
              the usage message, which defaults to $0.
              getopts places the next option letter it finds inside variable vname  each  time  it  is  invoked.   The
              option  letter will be prepended with a + when arg begins with a +.  The index of the next arg is stored
              in OPTIND.  The option argument, if any, gets stored in OPTARG.
              A leading : in optstring causes getopts to store the letter of an invalid option in OPTARG, and  to  set
              vname  to  ?   for  an  unknown  option and to : when a required option argument is missing.  Otherwise,
              getopts prints an error message.  The exit status is non-zero when there are no more options.
              There is no way to specify any of the options :, +, -, ?, [, and ].  The option # can only be  specified
              as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In  the  first  form, a range of commands from first to last is selected from the last HISTSIZE commands
              that were typed at the terminal.  The arguments first and last may be specified as  a  number  or  as  a
              string.   A string is used to locate the most recent command starting with the given string.  A negative
              number is used as an offset to the current command number.  If the -l option is selected,  the  commands
              are  listed  on  standard  output.   Otherwise, the editor program ename is invoked on a file containing
              these keyboard commands.  If ename is not supplied, then the value of the variable HISTEDIT is used.  If
              HISTEDIT is not set, then FCEDIT (default /bin/ed) is used as the editor.  When editing is complete, the
              edited command(s) is executed if the changes have been saved.  If last is not specified, then it will be
              set  to  first.   If first is not specified, the default is the previous command for editing and -16 for
              listing.  The option -r reverses the order of the commands and the option -n suppresses command  numbers
              when  listing.   In the second form, command is interpreted as first described above and defaults to the
              last command executed.  The resulting command is executed after the  optional  substitution  old=new  is
              performed.

       jobs [ -lnp ] [ job ... ]
              Lists  information about each given job; or all active jobs if job is omitted.  The -l option lists pro-
              cess ids in addition to the normal information.  The -n option only displays jobs that have  stopped  or
              exited  since  last notified.  The -p option causes only the process group to be listed.  See Jobs for a
              description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -Ll [ sig ... ]
              Sends either the TERM (terminate) signal or the specified signal to the  specified  jobs  or  processes.
              Signals  are  either given by number with the -n option or by name with the -s option (as given in <sig-
              nal.h>, stripped of the prefix ''SIG'' with the exception that SIGCLD is named CHLD).  For backward com-
              patibility,  the  n  and s can be omitted and the number or name placed immediately after the -.  If the
              signal being sent is TERM (terminate) or HUP (hangup), then the job or process will be sent a CONT (con-
              tinue)  signal if it is stopped.  The argument job can be the process id of a process that is not a mem-
              ber of one of the active jobs.  See Jobs for a description of the format of job.   In  the  third  form,
              kill  -l, or kill -L, if sig is not specified, the signal names are listed.  The -l option list only the
              signal names.  -L options lists each signal name and corresponding number.  Otherwise, for each sig that
              is  a  name,  the corresponding signal number is listed.  For each sig that is a number, the signal name
              corresponding to the least significant 8 bits of sig is listed.

       let arg ...
              Each arg is a separate arithmetic expression to be  evaluated.   let  only  recognizes  octal  constants
              starting  with 0 when the set option letoctal is on.  See Arithmetic Evaluation above, for a description
              of arithmetic expression evaluation.
              The exit status is 0 if the value of the last expression is non-zero, and 1 otherwise.

       + newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
              With no options or with option - or --, each arg is printed on standard output.  The  -f  option  causes
              the  arguments  to be printed as described by printf.  In this case, any e, n, r, R options are ignored.
              Otherwise, unless the -C, -R, -r, or -v are specified, the following escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and not adding a new-line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by the 1, 2, or 3-digit octal string given by x.

              The  -R  option  will print all subsequent arguments and options other than -n.  The -e causes the above
              escape conventions to be applied.  This is the default behavior.  It reverses the effect of  an  earlier
              -r.   The  -p  option  causes  the  arguments to be written onto the pipe of the process spawned with |&
              instead of standard output.  The -v option treats each arg as a variable name and writes  the  value  in
              the  printf  %B  format.   The  -C option treats each arg as a variable name and writes the value in the
              printf %#B format.  The -s option causes the arguments to be written onto the history  file  instead  of
              standard  output.   The -u option can be used to specify a one digit file descriptor unit number unit on
              which the output will be placed.  The default is 1.  If the option -n is used, no new-line is  added  to
              the output.

       printf format [ arg ... ]
              The  arguments arg are printed on standard output in accordance with the ANSI-C formatting rules associ-
              ated with the format string format.  If the number of arguments exceeds the number of format  specifica-
              tions,  the format string is reused to format remaining arguments.  The following extensions can also be
              used:
              %b     A %b format can be used instead of %s to cause escape sequences in the corresponding  arg  to  be
                     expanded as described in print.
              %B     A  %B option causes each of the arguments to be treated as variable names and the binary value of
                     variable will be printed.  The alternate flag # causes a compound variable to be output on a sin-
                     gle line.  This is most useful for compound variables and variables whose attribute is -b.
              %H     A %H format can be used instead of %s to cause characters in arg that are special in HTML and XML
                     to be output as their entity name.  The alternate flag # formats the output for use as a URI.
              %P     A %P format can be used instead of %s to cause arg to  be  interpreted  as  an  extended  regular
                     expression and be printed as a shell pattern.
              %R     A %R format can be used instead of %s to cause arg to be interpreted as a shell pattern and to be
                     printed as an extended regular expression.
              %q     A %q format can be used instead of %s to cause the resulting string to be quoted in a manner than
                     can  be  reinput  to  the  shell.  When q is preceded by the alternative format specifier, #, the
                     string is quoted in manner suitable as a field in a .csv format file.
              %(date-format)T
                     A %(date-format)T format can be use to treat an argument as a date/time string and to format  the
                     date/time according to the date-format as defined for the date(1) command.
              %Z     A %Z format will output a byte whose value is 0.
              %d     The  precision field of the %d format can be followed by a .  and the output base.  In this case,
                     the # flag character causes base# to be prepended.
              #      The # flag, when used with the %d format without an output base, displays the output in powers of
                     1000  indicated  by  one of the following suffixes: k M G T P E, and when used with the %i format
                     displays the output in powers of 1024 indicated by one of the following suffixes: Ki Mi Gi Ti  Pi
                     Ei.
              =      The = flag centers the output within the specified field width.
              L      The  L  flag, when used with the %c or %s formats, treats precision as character width instead of
                     byte count.
              ,      The , flag, when used with the %d or %f formats, separates groups of  digits  with  the  grouping
                     delimiter (, on groups of 3 in the C locale.)


       pwd [ -LP ]
              Outputs the value of the current working directory.  The -L option is the default; it prints the logical
              name of the current directory.  If the -P option is given, all symbolic  links  are  resolved  from  the
              name.  The last instance of -L or -P on the command line determines which method is used.

       read [ -ACSprsv ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u unit] [ vname?prompt ] [ vname ... ]
              The shell input mechanism.  One line is read and is broken up into fields using the characters in IFS as
              separators.  The escape character, \, is used to remove any special meaning for the next  character  and
              for line continuation.  The -d option causes the read to continue to the first character of delim rather
              than new-line.  The -n option causes at most n bytes to read rather a full line  but  will  return  when
              reading  from a slow device as soon as any characters have been read.  The -N option causes exactly n to
              be read unless an end-of-file has been encountered or the read times out because of the -t  option.   In
              raw mode, -r, the \ character is not treated specially.  The first field is assigned to the first vname,
              the second field to the second vname, etc., with leftover fields assigned to the last vname.  When vname
              has the binary attribute and -n or -N is specified, the bytes that are read are stored directly into the
              variable.  If the -v is specified, then the value of the first vname will be used  as  a  default  value
              when reading from a terminal device.  The -A option causes the variable vname to be unset and each field
              that is read to be stored in successive elements of the indexed array vname.  The -C option  causes  the
              variable  vname  to  be  read as a compound variable.  Blanks will be ignored when finding the beginning
              open parenthesis.  The -S option causes the line to be treated like a record in a .csv  format  file  so
              that  double  quotes  can  be used to allow the delimiter character and the new-line character to appear
              within a field.  The -p option causes the input line to be taken  from  the  input  pipe  of  a  process
              spawned by the shell using |&.  If the -s option is present, the input will be saved as a command in the
              history file.  The option -u can be used to specify a one digit file descriptor unit unit to read  from.
              The  file  descriptor can be opened with the exec special built-in command.  The default value of unit n
              is 0.  The option -t is used to specify a timeout in seconds when reading from a terminal or  pipe.   If
              vname  is  omitted,  then  REPLY is used as the default vname.  An end-of-file with the -p option causes
              cleanup for this process so that another can be spawned.  If  the  first  argument  contains  a  ?,  the
              remainder  of  this  word is used as a prompt on standard error when the shell is interactive.  The exit
              status is 0 unless an end-of-file is encountered or read has timed out.

       ++ readonly [ -p ] [ vname[=value] ] ...
              If vname is not given, the names and values of each variable with the readonly attribute is printed with
              the  values  quoted in a manner that allows them to be re-inputted.  The -p option causes the word read-
              only to be inserted before each one.  Otherwise, the given vnames are marked readonly  and  these  names
              cannot  be changed by subsequent assignment.  When defining a type, if the value of a readonly sub-vari-
              able is not defined the value is required when creating each instance.

       + return [ n ]
              Causes a shell function or .  script to return to the invoking script with the exit status specified  by
              n.   The  value will be the least significant 8 bits of the specified status.  If n is omitted, then the
              return status is that of the last command executed.  If return is invoked while not in a function or a .
              script, then it behaves the same as exit.

       + set [ ?BCGabefhkmnoprstuvx ] [ ?o [ option ] ] ... [ ?A vname ]  [ arg ... ]
              The options for this command have meaning as follows:
              -A      Array  assignment.   Unset  the variable vname and assign values sequentially from the arg list.
                      If +A is used, the variable vname is not unset first.
              -B      Enable brace pattern field generation.  This is the default behavior.
              -B      Enable brace group expansion.  On by default.
              -C      Prevents redirection > from truncating existing files.  Files that are created are  opened  with
                      the O_EXCL mode.  Requires >| to truncate a file when turned on.
              -G      Causes  the pattern ** by itself to match files and zero or more directories and sub-directories
                      when used for file name generation.  If followed by a / only directories and sub-directories are
                      matched.
              -a      All subsequent variables that are defined are automatically exported.
              -b      Prints job completion messages as soon as a background job changes state rather than waiting for
                      the next prompt.
              -e      Unless contained in a || or && command, or the command following an if while or until command or
                      in  the  pipeline following !, if a command has a non-zero exit status, execute the ERR trap, if
                      set, and exit.  This mode is disabled while reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first encountered.
              -k      (Obsolete). All variable assignment arguments are placed in the environment for a  command,  not
                      just those that precede the command name.
              -m      Background jobs will run in a separate process group and a line will print upon completion.  The
                      exit status of background jobs is reported in a completion message.  On systems  with  job  con-
                      trol, this option is turned on automatically for interactive shells.
              -n      Read  commands  and check them for syntax errors, but do not execute them.  Ignored for interac-
                      tive shells.
              -o      The following argument can be one of the following option names:
                      allexport
                              Same as -a.
                      errexit Same as -e.
                      bgnice  All background jobs are run at a lower priority.  This is the default mode.
                      braceexpand
                              Same as -B.
                      emacs   Puts you in an emacs style in-line editor for command entry.
                      globstar
                              Same as -G.
                      gmacs   Puts you in a gmacs style in-line editor for command entry.
                      ignoreeof
                              The shell will not exit on end-of-file.  The command exit must be used.
                      keyword Same as -k.
                      letoctal
                              The let command allows octal constants starting with 0.
                      markdirs
                              All directory names resulting from file name generation have a trailing / appended.
                      monitor Same as -m.
                      multiline
                              The built-in editors will use multiple lines on the screen for  lines  that  are  longer
                              than the width of the screen.  This may not work for all terminals.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do not save function definitions in the history file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A  pipeline  will  not complete until all components of the pipeline have completed, and
                              the return value will be the value of the last non-zero command to fail or  zero  if  no
                              command has failed.
                      showme  When enabled, simple commands or pipelines preceded by a semicolon (;) will be displayed
                              as if the xtrace option were enabled but will not be executed.  Otherwise, the leading ;
                              will be ignored.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      trackall
                              Same as -h.
                      vi      Puts  you in insert mode of a vi style in-line editor until you hit the escape character
                              033.  This puts you in control mode.  A return sends the line.
                      viraw   Each character is processed as it is typed in vi mode.
                      xtrace  Same as -x.
                      If no option name is supplied, then the current option settings are printed.
              -p      Disables processing of the $HOME/.profile file and uses the file  /etc/suid_profile  instead  of
                      the  ENV  file.   This  mode is on whenever the effective uid (gid) is not equal to the real uid
                      (gid).  Turning this off causes the effective uid and gid to be set to the real uid and gid.
              -r      Enables the restricted shell.  This option cannot be unset once set.
              -s      Sort the positional parameters lexicographically.
              -t      (Obsolete).  Exit after reading and executing one command.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do not change any of the options; useful in setting $1 to a value beginning with -.  If no argu-
                      ments follow this option then the positional parameters are unset.

              As an obsolete feature, if the first arg is - then the -x and -v options are turned off and the next arg
              is treated as the first argument.  Using + rather than - causes these options to be turned  off.   These
              options  can  also be used upon invocation of the shell.  The current set of options may be found in $-.
              Unless -A is specified, the remaining arguments are positional parameters and are assigned, in order, to
              $1  $2  ....   If  no arguments are given, then the names and values of all variables are printed on the
              standard output.

       + shift [ n ]
              The positional parameters from $n+1 ...  are renamed $1 ... , default n is 1.  The parameter  n  can  be
              any arithmetic expression that evaluates to a non-negative number less than or equal to $#.

       sleep seconds
              Suspends execution for the number of decimal seconds or fractions of a second given by seconds.

       + trap [ -p ] [ action ] [ sig ] ...
              The  -p  option  causes  the  trap  action associated with each trap as specified by the arguments to be
              printed with appropriate quoting.  Otherwise, action will be processed as if it were an argument to eval
              when  the shell receives signal(s) sig.  Each sig can be given as a number or as the name of the signal.
              Trap commands are executed in order of signal number.  Any attempt to set a trap on a  signal  that  was
              ignored  on entry to the current shell is ineffective.  If action is omitted and the first sig is a num-
              ber, or if action is -, then the trap(s) for each sig are reset to their original values.  If action  is
              the  null string then this signal is ignored by the shell and by the commands it invokes.  If sig is ERR
              then action will be executed whenever a command has a non-zero exit status.  If sig is DEBUG then action
              will be executed before each command.  The variable .sh.command will contain the contents of the current
              command line when action is running.  If the exit status of the trap is 2 the command will not  be  exe-
              cuted.  If the exit status of the trap is 255 and inside a function or a dot script, the function or dot
              script will return.  If sig is 0 or EXIT and the trap statement is executed inside the body of  a  func-
              tion  defined with the function name syntax, then the command action is executed after the function com-
              pletes.  If sig is 0 or EXIT for a trap set outside any function then the command action is executed  on
              exit  from  the  shell.   If  sig is KEYBD, then action will be executed whenever a key is read while in
              emacs, gmacs, or vi mode.  The trap command with no arguments prints a list of commands associated  with
              each signal number.

       An  exit  or  return  without  an  argument  in a trap action will preserve the exit status of the command that
       invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       ++ typeset [ ?ACHSfblmnprtux ] [ ?EFLRXZi[n] ]   [ +-M  [ mapname ] ] [ -T  [ tname=(assign_list) ] ] [ -h  str
       ] [ -a [type] ] [ vname[=value ]  ] ...
              Sets attributes and values for shell variables and functions.  When invoked inside  a  function  defined
              with the function name syntax, a new instance of the variable vname is created, and the variable's value
              and type are restored when the function completes.  The following list of attributes may be specified:
              -A     Declares vname to be an associative array.  Subscripts are strings rather than arithmetic expres-
                     sions.
              -C     causes  each  vname to be a compound variable.  value names a compound variable it is copied into
                     vname.  Otherwise, it unsets each vname.
              -a     Declares vname to be an indexed array.  If type is specified, it must be the name of an  enumera-
                     tion  type  created  with the enum command and it allows enumeration constants to be used as sub-
                     scripts.
              -E     Declares vname to be a double precision floating point number.  If n is non-zero, it defines  the
                     number  of  significant  figures  that are used when expanding vname.  Otherwise, ten significant
                     figures will be used.
              -F     Declares vname to be a double precision floating point number.  If n is non-zero, it defines  the
                     number  of  places  after  the  decimal  point that are used when expanding vname.  Otherwise ten
                     places after the decimal point will be used.
              -H     This option provides UNIX to host-name file mapping on non-UNIX machines.
              -L     Left justify and remove leading blanks from value.  If n is non-zero, it defines the width of the
                     field,  otherwise it is determined by the width of the value of first assignment.  When the vari-
                     able is assigned to, it is filled on the right with blanks or truncated,  if  necessary,  to  fit
                     into the field.  The -R option is turned off.
              -M     Use  the  character  mapping  mapping  defined  by  wctrans(3).  such as tolower and toupper when
                     assigning a value to each of the specified operands.  When mapping is specified and there are not
                     operands,  all  variables  that use this mapping are written to standard output.  When mapping is
                     omitted and there are no operands, all mapped variables are written to standard output.
              -R     Right justify and fill with leading blanks.  If n is non-zero, it defines the width of the field,
                     otherwise  it  is  determined  by  the width of the value of first assignment.  The field is left
                     filled with blanks or truncated from the end if the variable is reassigned.   The  -L  option  is
                     turned off.
              -S     When used within the assign_list of a type definition, it causes the specified sub-variable to be
                     shared by all instances of the type.  When used inside  a  function  defined  with  the  function
                     reserved  word, the specified variables will have function static scope.  Otherwise, the variable
                     is unset prior to processing the assignment list.
              -T     If followed by tname, it creates a type named by tname using the compound assignment  assign_list
                     to tname.  Otherwise, it writes all the type definitions to standard output.
              -X     Declares  vname to be a double precision floating point number and expands using the %a format of
                     ISO-C99.  If n is non-zero, it defines the number of hex digits after the  radix  point  that  is
                     used when expanding vname.  The default is 10.
              -Z     Right  justify and fill with leading zeros if the first non-blank character is a digit and the -L
                     option has not been set.  Remove leading zeros if the -L option is also set.  If n  is  non-zero,
                     it  defines the width of the field, otherwise it is determined by the width of the value of first
                     assignment.
              -f     The names refer to function names rather than variable names.  No assignments can be made and the
                     only  other  valid  options  are -S, -t, -u and -x.  The -S can be used with discipline functions
                     defined in a type to indicate that the function is static.   For  a  static  function,  the  same
                     method  will  be  used  by all instances of that type no matter which instance references it.  In
                     addition, it can only use value of variables from the original type definition.  These discipline
                     functions cannot be redefined in any type instance.  The -t option turns on execution tracing for
                     this function.  The -u option causes this function to be marked undefined.   The  FPATH  variable
                     will  be searched to find the function definition when the function is referenced.  If no options
                     other than -f is specified, then the function definition will be displayed  on  standard  output.
                     If +f is specified, then a line containing the function name followed by a shell comment contain-
                     ing the line number and path name of the file where this function was defined, if  any,  is  dis-
                     played.  The exit status can be used to determine whether the function is defined so that typeset
                     -f .sh.math.name will return 0 when math function name is defined and non-zero otherwise.
              -b     The variable can hold any number of bytes of data.  The data can be text or binary.  The value is
                     represented  by  the  base64 encoding of the data.  If -Z is also specified, the size in bytes of
                     the data in the buffer will be determined by the size associated with  the  -Z.   If  the  base64
                     string  assigned  results  in more data, it will be truncated.  Otherwise, it will be filled with
                     bytes whose value is zero.  The printf format %B can be used to output the actual  data  in  this
                     buffer instead of the base64 encoding of the data.
              -h     Used  within  type definitions to add information when generating information about the sub-vari-
                     able on the man page.  It is ignored when used outside of a type definition.  When used  with  -f
                     the information is associated with the corresponding discipline function.
              -i     Declares  vname to be represented internally as integer.  The right hand side of an assignment is
                     evaluated as an arithmetic expression when assigning to an integer.  If n is non-zero, it defines
                     the output arithmetic base, otherwise the output base will be ten.
              -l     Used with -i, -E or -F, to indicate long integer, or long float.  Otherwise, all upper-case char-
                     acters are converted to lower-case.  The upper-case option, -u, is turned off.  Equivalent to  -M
                     tolower .
              -m     moves  or renames the variable.  The value is the name of a variable whose value will be moved to
                     vname.  The original variable will be unset.  Cannot be used with any other options.
              -n     Declares vname to be a reference to the variable whose name is defined by the value  of  variable
                     vname.  This is usually used to reference a variable inside a function whose name has been passed
                     as an argument.  Cannot be used with any other options.
              -p     The name, attributes and values for the given vnames are written on standard  output  in  a  form
                     that can be used as shell input.  If +p is specified, then the values are not displayed.
              -r     The  given vnames are marked readonly and these names cannot be changed by subsequent assignment.
              -t     Tags the variables.  Tags are user definable and have no special meaning to the shell.
              -u     When given along with -i, specifies unsigned integer.  Otherwise, all lower-case  characters  are
                     converted to upper-case.  The lower-case option, -l, is turned off.  Equivalent to -M toupper .
              -x     The given vnames are marked for automatic export to the environment of subsequently-executed com-
                     mands.  Variables whose names contain a .  cannot be exported.

              The -i attribute cannot be specified along with -R, -L, -Z, or -f.

              Using + rather than - causes these options to be turned off.  If no vname arguments are given, a list of
              vnames (and optionally the values) of the variables is printed.  (Using + rather than - keeps the values
              from being printed.)  The -p option causes typeset followed by the option letters to be  printed  before
              each  name rather than the names of the options.  If any option other than -p is given, only those vari-
              ables which have all of the given options are printed.  Otherwise, the  vnames  and  attributes  of  all
              variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set  or  display a resource limit.  The available resource limits are listed below.  Many systems do not
              support one or more of these limits.  The limit for a specified resource is set when limit is specified.
              The  value  of limit can be a number in the unit specified below with each resource, or the value unlim-
              ited.  The -H and -S options specify whether the hard limit or the soft limit for the given resource  is
              set.  A hard limit cannot be increased once it is set.  A soft limit can be increased up to the value of
              the hard limit.  If neither the H nor S option is specified, the limit applies  to  both.   The  current
              resource  limit  is  printed when limit is omitted.  In this case, the soft limit is printed unless H is
              specified.  When more than one resource is specified, then the limit name and unit is printed before the
              value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The  number  of  512-byte  blocks on files that can be written by the current process or by child
                     processes (files of any size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
              The user file-creation mask is set to mask (see umask(2)).  mask can either be an octal number or a sym-
              bolic  value as described in chmod(1).  If a symbolic value is given, the new umask value is the comple-
              ment of the result of applying mask to the complement of the previous umask value.  If mask is  omitted,
              the  current  value  of  the mask is printed.  The -S option causes the mode to be printed as a symbolic
              value.  Otherwise, the mask is printed in octal.

       + unalias [ -a ] name ...
              The aliases given by the list of names are removed from the alias list.  The -a option  causes  all  the
              aliases to be unset.

       +unset [ -fnv ] vname ...
              The  variables given by the list of vnames are unassigned, i.e., except for sub-variables within a type,
              their values and attributes are erased.  For sub-variables of a  type,  the  values  are  reset  to  the
              default  value  from the type definition.  Readonly variables cannot be unset.  If the -f option is set,
              then the names refer to function names.  If the -v option is set,  then  the  names  refer  to  variable
              names.   The -f option overrides -v.  If -n is set and name is a name reference, then name will be unset
              rather than the variable that it references.  The  default  is  equivalent  to  -v.   Unsetting  LINENO,
              MAILCHECK,  OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their special meaning even if they are
              subsequently assigned to.

       wait [ job ... ]
              Wait for the specified job and report its termination status.  If job is not given, then  all  currently
              active  child  processes  are waited for.  The exit status from this command is that of the last process
              waited for if job is specified; otherwise it is zero.  See Jobs for a description of the format of  job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a command name.
              The  -v  option  produces  a more verbose report.  The -f option skips the search for functions.  The -p
              option does a path search for name even if name is an alias, a function, or a  reserved  word.   The  -p
              option  turns  off  the -v option.  The -a option is similar to the -v option but causes all interpreta-
              tions of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument zero ($0)  is  -,  then  the  shell  is
       assumed  to  be a login shell and commands are read from /etc/profile and then from either .profile in the cur-
       rent directory or $HOME/.profile, if either file exists.  Next, for interactive shells, commands are read  from
       the  file  named  by  performing  parameter expansion, command substitution, and arithmetic substitution on the
       value of the environment variable ENV if the file exists.  If the -s option is not present and arg and  a  file
       by  the  name of arg exists, then it reads and executes this script.  Otherwise, if the first arg does not con-
       tain a /, a path search is performed on the first arg to determine the name of  the  script  to  execute.   The
       script  arg  must have execute permission and any setuid and setgid settings will be ignored.  If the script is
       not found on the path, arg is processed as if it named a built-in command or function.  Commands are then  read
       as described below; the following options are interpreted by the shell when it is invoked:

       -D      Do  not execute the script, but output the set of double quoted strings preceded by a $.  These strings
               are needed for localization of the script to different locales.
       -E      Reads the file named by the ENV variable or by $HOME/.kshrc if not defined after the profiles.
       -c        If the -c option is present, then commands are read from the  first  arg.   Any  remaining  arguments
                 become positional parameters starting at 0.
       -s        If  the  -s  option  is  present  or if no arguments remain, then commands are read from the standard
                 input.  Shell output, except for the output of the Special Commands listed above, is written to  file
                 descriptor 2.
       -i        If  the  -i  option  is present or if the shell input and error output are attached to a terminal (as
                 told by tcgetattr(2)), then this shell is interactive.  In this case TERM is ignored (so that kill  0
                 does not kill an interactive shell) and INTR is caught and ignored (so that wait is ).  In all cases,
                 QUIT is ignored by the shell.
       -r        If the -r option is present, the shell is a restricted shell.
       -D        A list of all double quoted strings that are preceded by a $ will be printed on standard  output  and
                 the  shell will exit.  This set of strings will be subject to language translation when the locale is
                 not C or POSIX.  No commands will be executed.

       -P        If -P or -o profile is present, the shell is a profile shell (see pfexec(1)).

       -R filename
                 The -R filename option is used to generate a cross reference database that can be used by a  separate
                 utility  to find definitions and references for variables and commands.  The filename argument speci-
                 fies the generated database. A script file must be provided on the command line as well.

       The remaining options and arguments are described under the set command above.  An  optional  -  as  the  first
       argument is ignored.

   Rksh Only.
       Rksh is used to set up login names and execution environments whose capabilities are more controlled than those
       of the standard shell.  The actions of rksh are identical to those of ksh, except that the following are disal-
       lowed:
              Unsetting the restricted option.
              changing directory (see cd(1)),
              setting or unsetting the value or attributes of SHELL, ENV, FPATH, or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The restrictions above are enforced after .profile and the ENV files are interpreted.

       When  a  command  to be executed is found to be a shell procedure, rksh invokes ksh to execute it.  Thus, it is
       possible to provide to the end-user shell procedures that have access to the full power of the standard  shell,
       while  imposing  a limited menu of commands; this scheme assumes that the end-user does not have write and exe-
       cute permissions in the same directory.

       The net effect of these rules is that the writer of the .profile has complete control  over  user  actions,  by
       performing  guaranteed  setup  actions and leaving the user in an appropriate directory (probably not the login
       directory).

       The system administrator often sets up a directory of commands (e.g., /usr/rbin) that can be safely invoked  by
       rksh.

EXIT STATUS
       Errors  detected by the shell, such as syntax errors, cause the shell to return a non-zero exit status.  If the
       shell is being used non-interactively, then execution of the shell file is abandoned unless  the  error  occurs
       inside a subshell in which case the subshell is abandoned.  Otherwise, the shell returns the exit status of the
       last command executed (see also the exit command above).  Run time errors detected by the shell are reported by
       printing  the  command or function name and the error condition.  If the line number that the error occurred on
       is greater than one, then the line number is also printed in square brackets ([]) after the command or function
       name.

FILES
       /etc/profile
              The system wide initialization file, executed for login shells.

       $HOME/.profile
              The personal initialization file, executed for login shells after /etc/profile.

       $HOME/..kshrc
              Default personal initialization file, executed for interactive shells when ENV is not set.

       /etc/suid_profile
              Alternative  initialization file, executed instead of the personal initialization file when the real and
              effective user or group id do not match.

       /dev/null
              NULL device

SEE ALSO
       cat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1), fgrep(1), gmacs(1),  grep(1),  newgrp(1),
       pfexec(1),  stty(1),  test(1),  umask(1),  vi(1),  dup(2),  exec(2),  fork(2), getpwnam(3), ioctl(2), lseek(2),
       paste(1), pathconf(2), pipe(2), sysconf(2), umask(2), ulimit(2), wait(2), wctrans(3), rand(3),  a.out(5),  pro-
       file(5), environ(7).

       Morris I. Bolsky and David G. Korn, The New KornShell Command and Programming Language, Prentice Hall, 1995.

       POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.

CAVEATS
       If  a command is executed, and then a command with the same name is installed in a directory in the search path
       before the directory where the original command was found, the shell will continue to exec  the  original  com-
       mand.  Use the -t option of the alias command to correct this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe character |.

       Using  the  hist  built-in command within a compound command will cause the whole command to disappear from the
       history file.

       The built-in command . file reads the whole file before any commands are executed.  Therefore, alias  and  una-
       lias commands in the file will not apply to any commands defined in the file.

       Traps  are  not  processed while a job is waiting for a foreground process.  Thus, a trap on CHLD won't be exe-
       cuted until the foreground job terminates.

       It is a good idea to leave a space after the comma operator in arithmetic expressions to prevent the comma from
       being interpreted as the decimal point character in certain locales.



                                                                        KSH(1)