PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

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

NAME         top

       getopts — parse utility options

SYNOPSIS         top

       getopts optstring name [arg...]

DESCRIPTION         top

       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.1‐2008, 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         top

       None.

OPERANDS         top

       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.1‐2008.)
                 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         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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.1‐2008, 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         top

       Default.

STDOUT         top

       Not used.

STDERR         top

       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         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       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         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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         top

       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         top

       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         top

       None.

SEE ALSO         top

       Section 2.5.2, Special Parameters

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

       The System Interfaces volume of POSIX.1‐2008, getopt(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                         GETOPTS(1P)