GETOPTS(1)                 POSIX Programmer's Manual                GETOPTS(1)



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

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
       POSIX.1-2017, 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 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; 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 operand, or the value ""$$##""+1 if there
       are no operands; the name variable shall be set to the <question-mark>
       character. Any of the following shall identify the end of options: the
       first ""----"" argument that is not an option-argument, finding an argument
       that is not an option-argument and 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 Section 2.12,
       Shell Execution Environment.

       If the application sets OPTIND to the value 1, a new set of parameters
       can be used: either the current positional parameters or new arg
       values. Any other attempt to invoke getopts multiple times in a single
       shell execution environment with parameters (positional parameters or
       arg operands) that are not the same in all invocations, 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
                 POSIX.1-2017.) 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 POSIX.1-2017, Section 8.2, Internationalization
                 Variables for the precedence 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 example, 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 written 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 diagnostic 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 Section 2.5.2, 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
       following:


           (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
       unspecified.

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>
       characters.

       The OPTARG variable is not mentioned in the ENVIRONMENT VARIABLES
       section because it does not affect the execution 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 specified 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 messages
       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
       Section 2.5.2, Special Parameters

       The Base Definitions volume of POSIX.1-2017, Chapter _8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

       The System Interfaces volume of POSIX.1-2017, getopt()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 Standard, 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                           GETOPTS(1)
