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GETOPTS(1P)                POSIX Programmer's Manual               GETOPTS(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
       getopts - parse utility options

SYNOPSIS
       getopts optstring name [arg...]

DESCRIPTION
       The getopts utility shall retrieve options and option-arguments from a list of parameters. It shall support the
       Utility Syntax Guidelines 3 to 10, inclusive, described in the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines.

       Each  time  it  is  invoked, the getopts utility shall place the value of the next option in the shell variable
       specified by the name operand and the index of the next argument to be processed in the shell variable  OPTIND.
       Whenever the shell is invoked, OPTIND shall be initialized to 1.

       When  the  option requires an option-argument, the getopts utility shall place it in the shell variable OPTARG.
       If no option was found, or if the option that was found does not  have  an  option-argument,  OPTARG  shall  be
       unset.

       If  an  option character not contained in the optstring operand is found where an option character is expected,
       the shell variable specified by name shall be set to the question-mark ( '?' ) character. In this case, if  the
       first character in optstring is a colon ( ':' ), the shell variable OPTARG shall be set to the option character
       found, but no output shall be written to standard error; otherwise, the shell variable OPTARG  shall  be  unset
       and  a diagnostic message shall be written to standard error. This condition shall be considered to be an error
       detected in the way arguments were presented to the invoking application, but shall not be an error in  getopts
       processing.

       If an option-argument is missing:

        * If  the  first  character  of optstring is a colon, the shell variable specified by name shall be set to the
          colon character and the shell variable OPTARG shall be set to the option character found.


        * Otherwise, the shell variable specified by name shall be set to the question-mark character, the shell vari-
          able  OPTARG  shall  be  unset,  and a diagnostic message shall be written to standard error. This condition
          shall be considered to be an error detected in the way arguments were presented to the invoking application,
          but  shall  not  be an error in getopts processing; a diagnostic message shall be written as stated, but the
          exit status shall be zero.


       When the end of options is encountered, the getopts utility shall exit with a return value greater  than  zero;
       the  shell  variable  OPTIND  shall  be set to the index of the first non-option-argument, where the first "--"
       argument is considered to be an option-argument if there are no other non-option-arguments appearing before it,
       or  the value "$#" +1 if there are no non-option-arguments; the name variable shall be set to the question-mark
       character. Any of the following shall identify the end of options: the special option "--", finding an argument
       that does not begin with a '-', or encountering an error.

       The  shell  variables  OPTIND  and  OPTARG shall be local to the caller of getopts and shall not be exported by
       default.

       The shell variable specified by the name operand, OPTIND , and OPTARG shall affect the current shell  execution
       environment; see Shell Execution Environment .

       If  the  application  sets OPTIND to the value 1, a new set of parameters can be used: either the current posi-
       tional parameters or new arg values. Any other attempt to invoke getopts multiple times in a single shell  exe-
       cution environment with parameters (positional parameters or arg operands) that are not the same in all invoca-
       tions, or with an OPTIND value modified to be a value other than 1, produces unspecified results.

OPTIONS
       None.

OPERANDS
       The following operands shall be supported:

       optstring
              A string containing the option characters recognized by the utility invoking getopts. If a character  is
              followed  by  a  colon,  the option shall be expected to have an argument, which should be supplied as a
              separate argument. Applications should specify an option character and its option-argument  as  separate
              arguments,  but getopts shall interpret the characters following an option character requiring arguments
              as an argument whether or not this is done. An explicit null option-argument need not be  recognized  if
              it  is  not  supplied  as  a  separate argument when getopts is invoked. (See also the getopt() function
              defined in the System Interfaces volume of  IEEE Std 1003.1-2001.)   The  characters  question-mark  and
              colon  shall not be used as option characters by an application. The use of other option characters that
              are not alphanumeric produces unspecified results. If the option-argument is not supplied as a  separate
              argument  from  the  option character, the value in OPTARG shall be stripped of the option character and
              the '-' . The first character in optstring determines how getopts behaves if an option character is  not
              known or an option-argument is missing.

       name   The  name  of a shell variable that shall be set by the getopts utility to the option character that was
              found.


       The getopts utility by default shall parse positional parameters passed to the  invoking  shell  procedure.  If
       args are given, they shall be parsed instead of the positional parameters.

STDIN
       Not used.

INPUT FILES
       None.

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

       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 and input files).

       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 .

       OPTIND This variable shall be used by the getopts utility as the index of the next argument to be processed.


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Not used.

STDERR
       Whenever an error is detected and the first character in the optstring operand is not a colon ( ':' ), a  diag-
       nostic message shall be written to standard error with the following information in an unspecified format:

        * The  invoking  program name shall be identified in the message. The invoking program name shall be the value
          of the shell special parameter 0 (see Special Parameters ) at the time the getopts  utility  is  invoked.  A
          name equivalent to:


          basename "$0"

       may be used.


        * If  an  option is found that was not specified in optstring, this error is identified and the invalid option
          character shall be identified in the message.


        * If an option requiring an option-argument is found, but an option-argument is not found, this error shall be
          identified and the invalid option character shall be identified in the message.


OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     An option, specified or unspecified by optstring, was found.

       >0     The end of options was encountered or an error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       Since  getopts  affects  the  current  shell execution environment, it is generally provided as a shell regular
       built-in. If it is called in a subshell or separate utility execution environment, such as one of  the  follow-
       ing:


              (getopts abc value "$@")
              nohup getopts ...
              find . -exec getopts ... \;

       it does not affect the shell variables in the caller's environment.

       Note  that  shell  functions  share  OPTIND  with  the  calling shell even though the positional parameters are
       changed. If the calling shell and any of its functions uses getopts to parse arguments, the results are unspec-
       ified.

EXAMPLES
       The following example script parses and displays its arguments:


              aflag=
              bflag=
              while getopts ab: name
              do
                  case $name in
                  a)    aflag=1;;
                  b)    bflag=1
                        bval="$OPTARG";;
                  ?)    printf "Usage: %s: [-a] [-b value] args\n" $0
                        exit 2;;
                  esac
              done
              if [ ! -z "$aflag" ]; then
                  printf "Option -a specified\n"
              fi
              if [ ! -z "$bflag" ]; then
                  printf 'Option -b "%s" specified\n' "$bval"
              fi
              shift $(($OPTIND - 1))
              printf "Remaining arguments are: %s\n" "$*"

RATIONALE
       The  getopts  utility  was  chosen in preference to the System V getopt utility because getopts handles option-
       arguments containing <blank>s.

       The OPTARG variable is not mentioned in the ENVIRONMENT VARIABLES section because it does not affect the execu-
       tion of getopts; it is one of the few "output-only" variables used by the standard utilities.

       The  colon  is  not allowed as an option character because that is not historical behavior, and it violates the
       Utility Syntax Guidelines. The colon is now specified to behave as in the  KornShell  version  of  the  getopts
       utility;  when used as the first character in the optstring operand, it disables diagnostics concerning missing
       option-arguments and unexpected option characters. This replaces the use of the OPTERR variable that was speci-
       fied in an early proposal.

       The  formats of the diagnostic messages produced by the getopts utility and the getopt() function are not fully
       specified because implementations with superior (''friendlier") formats objected to the formats  used  by  some
       historical  implementations.  The  standard developers considered it important that the information in the mes-
       sages used be uniform between getopts and getopt(). Exact duplication of the messages might  not  be  possible,
       particularly  if  a utility is built on another system that has a different getopt() function, but the messages
       must have specific information included so that the program name, invalid option character, and type  of  error
       can be distinguished by a user.

       Only  a  rare application program intercepts a getopts standard error message and wants to parse it. Therefore,
       implementations are free to choose the most usable messages they can devise. The following formats are used  by
       many historical implementations:


              "%s: illegal option -- %c\n", <program name>, <option character>


              "%s: option requires an argument -- %c\n", <program name>, \
                  <option character>

       Historical  shells  with  built-in  versions of getopt() or getopts have used different formats, frequently not
       even indicating the option character found in error.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Special Parameters, the System Interfaces volume of IEEE Std 1003.1-2001, getopt()

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                          GETOPTS(1P)