getopts(1p) — Linux manual page

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.1‐2017, 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         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.1‐2017.) 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         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.1‐2017, 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         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.1‐2017, Chapter 8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

       The System Interfaces volume of POSIX.1‐2017, getopt(3p)

COPYRIGHT         top

       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(1P)

Pages that refer to this page: pax(1p)getopt(3p)