Man Pages

test(1p) - phpMan test(1p) - phpMan

Command: man perldoc info search(apropos)  


TEST(1P)                   POSIX Programmer's Manual                  TEST(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       test - evaluate expression

SYNOPSIS
       test [expression]

       [ [expression] ]


DESCRIPTION
       The test utility shall evaluate the expression and indicate the result of the evaluation by its exit status. An
       exit status of zero indicates that the expression evaluated as true and an exit status of 1 indicates that  the
       expression evaluated as false.

       In  the  second  form  of  the utility, which uses "[]" rather than test, the application shall ensure that the
       square brackets are separate arguments.

OPTIONS
       The test utility shall not recognize the "--" argument in the manner specified by guideline 10 in the Base Def-
       initions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       No options shall be supported.

OPERANDS
       The  application  shall ensure that all operators and elements of primaries are presented as separate arguments
       to the test utility.

       The following primaries can be used to construct expression:

       -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 a regular file.

       -g  file
              True if file exists and its set-group-ID flag is set.

       -h  file
              True if file exists and is a symbolic link.

       -L  file
              True if file exists and is a symbolic link.

       -n  string
              True if the length of string is non-zero.

       -p  file
              True if file is a FIFO.

       -r  file
              True if file exists and is readable. True shall indicate that permission  to  read  from  file  will  be
              granted, as defined in File Read, Write, and Creation .

       -S  file
              True if file exists and is a socket.

       -s  file
              True if file exists and has a size greater than zero.

       -t  file_descriptor

              True if the file whose file descriptor number is file_descriptor is open and is associated with a termi-
              nal.

       -u  file
              True if file exists and its set-user-ID flag is set.

       -w  file
              True if file exists and is writable. True shall indicate that permission to  write  from  file  will  be
              granted, as defined in File Read, Write, and Creation .

       -x  file
              True  if  file  exists  and  is  executable. True shall indicate that permission to execute file will be
              granted, as defined in File Read, Write, and Creation . If file is a directory, true shall indicate that
              permission to search file will be granted.

       -z  string
              True if the length of string string is zero.

       string True if the string string is not the null string.

       s1 =  s2
              True if the strings s1 and s2 are identical.

       s1 !=  s2
              True if the strings s1 and s2 are not identical.

       n1 -eq  n2
              True if the integers n1 and n2 are algebraically equal.

       n1 -ne  n2
              True if the integers n1 and n2 are not algebraically equal.

       n1 -gt  n2
              True if the integer n1 is algebraically greater than the integer n2.

       n1 -ge  n2
              True if the integer n1 is algebraically greater than or equal to the integer n2.

       n1 -lt  n2
              True if the integer n1 is algebraically less than the integer n2.

       n1 -le  n2
              True if the integer n1 is algebraically less than or equal to the integer n2.

       expression1 -a  expression2

              True  if  both expression1 and expression2 are true. The -a binary primary is left associative. It has a
              higher precedence than -o.

       expression1 -o  expression2

              True if either expression1 or expression2 is true. The -o binary primary is left associative.


       With the exception of the -h file and -L file primaries, if a file argument is  a  symbolic  link,  test  shall
       evaluate the expression by resolving the symbolic link and using the file referenced by the link.

       These primaries can be combined with the following operators:

       !  expression
              True if expression is false.

       (  expression  )
              True  if  expression is true. The parentheses can be used to alter the normal precedence and associativ-
              ity.


       The primaries with two elements of the form:


              -primary_operator primary_operand

       are known as unary primaries. The primaries with three elements in either of the two forms:


              primary_operand -primary_operator primary_operand


              primary_operand primary_operator primary_operand

       are known as binary primaries. Additional implementation-defined operators and primary_operators  may  be  pro-
       vided  by  implementations. They shall be of the form - operator where the first character of operator is not a
       digit.

       The algorithm for determining the precedence of the operators and the return value that shall be  generated  is
       based  on  the  number of arguments presented to test. (However, when using the "[...]" form, the right-bracket
       final argument shall not be counted in this algorithm.)

       In the following list, $1, $2, $3, and $4 represent the arguments presented to test:

       0 arguments:
              Exit false (1).

       1 argument:
              Exit true (0) if $1 is not null; otherwise, exit false.

       2 arguments:

               * If $1 is '!', exit true if $2 is null, false if $2 is not null.


               * If $1 is a unary primary, exit true if the unary test is true, false if the unary test is false.


               * Otherwise, produce unspecified results.


       3 arguments:

               * If $2 is a binary primary, perform the binary test of $1 and $3.


               * If $1 is '!', negate the two-argument test of $2 and $3.


               * If $1 is '(' and $3 is ')', perform the unary test of $2.


               * Otherwise, produce unspecified results.


       4 arguments:

               * If $1 is '!', negate the three-argument test of $2, $3, and $4.


               * If $1 is '(' and $4 is ')', perform the two-argument test of $2 and $3.


               * Otherwise, the results are unspecified.


       >4 arguments:
              The results are unspecified.

       On XSI-conformant systems, combinations of primaries and operators shall be evaluated using the precedence  and
       associativity  rules  described  previously.  In  addition, the string comparison binary primaries '=' and "!="
       shall have a higher precedence than any unary primary.


STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of test:

       LANG   Provide a default value for the internationalization variables that are unset or  null.  (See  the  Base
              Definitions  volume  of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the prece-
              dence of internationalization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_CTYPE
              Determine  the locale for the interpretation of sequences of bytes of text data as characters (for exam-
              ple, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
              Determine the locale that should be used to affect the format and contents of diagnostic messages  writ-
              ten to standard error.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Not used.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     expression evaluated to true.

        1     expression evaluated to false or expression was missing.

       >1     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       Scripts should be careful when dealing with user-supplied input that could be confused with primaries and oper-
       ators. Unless the application writer knows all the cases that produce input to the script, invocations like:


              test "$1" -a "$2"

       should be written as:


              test "$1" && test "$2"

       to avoid problems if a user supplied values such as $1 set to '!'  and $2 set to the null string. That  is,  in
       cases where maximal portability is of concern, replace:


              test expr1 -a expr2

       with:


              test expr1 && test expr2

       and replace:


              test expr1 -o expr2

       with:


              test expr1 || test expr2

       but  note  that,  in  test,  -a  has higher precedence than -o while "&&" and "||" have equal precedence in the
       shell.

       Parentheses or braces can be used in the shell command language to effect grouping.

       Parentheses must be escaped when using sh; for example:


              test \( expr1 -a expr2 \) -o expr3

       This command is not always portable outside XSI-conformant systems.  The following form can be used instead:


              ( test expr1 && test expr2 ) || test expr3

       The two commands:


              test "$1"
              test ! "$1"

       could not be used reliably on some historical systems. Unexpected results would occur if such a string  expres-
       sion were used and $1 expanded to '!', '(', or a known unary primary.  Better constructs are:


              test -n "$1"
              test -z "$1"
       respectively.

       Historical systems have also been unreliable given the common construct:


              test "$response" = "expected string"

       One of the following is a more reliable form:


              test "X$response" = "Xexpected string"
              test "expected string" = "$response"

       Note  that  the  second  form  assumes  that  expected  string could not be confused with any unary primary. If
       expected string starts with '-', '(', '!', or even '=', the first form should be used instead.  Using the  pre-
       ceding rules without the XSI marked extensions, any of the three comparison forms is reliable, given any input.
       (However, note that the strings are quoted in all cases.)

       Because the string comparison binary primaries, '=' and "!=", have a higher precedence than any  unary  primary
       in  the  greater than 4 argument case, unexpected results can occur if arguments are not properly prepared. For
       example, in:


              test -d $1 -o -d $2

       If $1 evaluates to a possible directory name of '=', the first three arguments are considered a string compari-
       son,  which  shall cause a syntax error when the second -d is encountered.  One of the following forms prevents
       this; the second is preferred:


              test \( -d "$1" \) -o \( -d "$2" \)
              test -d "$1" || test -d "$2"

       Also in the greater than 4 argument case:


              test "$1" = "bat" -a "$2" = "ball"

       syntax errors occur if $1 evaluates to '(' or '!' . One of the following forms prevents this; the third is pre-
       ferred:


              test "X$1" = "Xbat" -a "X$2" = "Xball"
              test "$1" = "bat" && test "$2" = "ball"
              test "X$1" = "Xbat" && test "X$2" = "Xball"

EXAMPLES
        1. Exit if there are not two or three arguments (two variations):


           if [ $# -ne 2 -a $# -ne 3 ]; then exit 1; fi
           if [ $# -lt 2 -o $# -gt 3 ]; then exit 1; fi


        2. Perform a mkdir if a directory does not exist:


           test ! -d tempdir && mkdir tempdir


        3. Wait for a file to become non-readable:


           while test -r thefile
           do
               sleep 30
           done
           echo '"thefile" is no longer readable'


        4. Perform a command if the argument is one of three strings (two variations):


           if [ "$1" = "pear" ] || [ "$1" = "grape" ] || [ "$1" = "apple" ]
           then
               command
           fi


           case "$1" in
               pear|grape|apple) command ;;
           esac


RATIONALE
       The  KornShell-derived  conditional  command  (double bracket [[]]) was removed from the shell command language
       description in an early proposal. Objections were raised that the real problem is misuse of the test command  (
       [),  and putting it into the shell is the wrong way to fix the problem. Instead, proper documentation and a new
       shell reserved word ( !) are sufficient.

       Tests that require multiple test operations can be done at the shell level using individual invocations of  the
       test command and shell logicals, rather than using the error-prone -o flag of test.

       XSI-conformant systems support more than four arguments.

       XSI-conformant systems support the combining of primaries with the following constructs:

       expression1 -a expression2

              True if both expression1 and expression2 are true.

       expression1 -o expression2

              True if at least one of expression1 and expression2 are true.

       ( expression )

              True if expression is true.


       In evaluating these more complex combined expressions, the following precedence rules are used:

        * The unary primaries have higher precedence than the algebraic binary primaries.


        * The unary primaries have lower precedence than the string binary primaries.


        * The unary and binary primaries have higher precedence than the unary string primary.


        * The  !  operator  has higher precedence than the -a operator, and the -a operator has higher precedence than
          the -o operator.


        * The -a and -o operators are left associative.


        * The parentheses can be used to alter the normal precedence and associativity.


       The BSD and System V versions of -f are not the same. The BSD definition was:

       -f  file
              True if file exists and is not a directory.


       The SVID  version  (true  if  the  file  exists  and  is  a  regular  file)  was  chosen  for  this  volume  of
       IEEE Std 1003.1-2001  because its use is consistent with the -b, -c, -d, and -p operands ( file exists and is a
       specific file type).

       The -e primary, possessing similar functionality to that provided by the C shell, was added because it provides
       the only way for a shell script to find out if a file exists without trying to open the file. Since implementa-
       tions are allowed to add additional file types, a portable script cannot use:


              test -b foo -o -c foo -o -d foo -o -f foo -o -p foo

       to find out if foo is an existing file. On historical BSD systems, the existence of a file could be  determined
       by:


              test -f foo -o -d foo

       but  there  was  no  easy way to determine that an existing file was a regular file. An early proposal used the
       KornShell -a primary (with the same meaning), but this was changed to -e because there were concerns about  the
       high probability of humans confusing the -a primary with the -a binary operator.

       The  following  options were not included in this volume of IEEE Std 1003.1-2001, although they are provided by
       some implementations. These operands should not be used by new implementations for other purposes:

       -k  file
              True if file exists and its sticky bit is set.

       -C  file
              True if file is a contiguous file.

       -V  file
              True if file is a version file.


       The following option was not included because it was undocumented in most  implementations,  has  been  removed
       from  some  implementations (including System V), and the functionality is provided by the shell (see Parameter
       Expansion .

       -l  string
              The length of the string string.


       The -b, -c, -g, -p, -u, and -x operands are derived from the SVID; historical BSD does not provide them. The -k
       operand is derived from System V; historical BSD does not provide it.

       On historical BSD systems, test -w directory always returned false because test tried to open the directory for
       writing, which always fails.

       Some additional primaries newly invented or from the KornShell appeared in an early proposal  as  part  of  the
       conditional  command ( [[]]): s1 > s2, s1 < s2, str = pattern, str != pattern, f1 -nt f2, f1 -ot f2, and f1 -ef
       f2. They were not carried forward into the test utility when the conditional command was removed from the shell
       because  they  have not been included in the test utility built into historical implementations of the sh util-
       ity.

       The -t file_descriptor primary is shown with a mandatory argument because the grammar is ambiguous if it can be
       omitted. Historical implementations have allowed it to be omitted, providing a default of 1.

FUTURE DIRECTIONS
       None.

SEE ALSO
       File Read, Write, and Creation, find

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  Issue  6,  Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                             TEST(1P)