GETOPTS
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
PROLOG
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
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
If an option-argument is missing:
* |
If the first character of optstring is a |
||
* |
Otherwise, the shell variable specified by name shall be set to the |
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
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 |
||
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
* |
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] argsn” $0
exit 2;;
esac
done
if [ ! -z “$aflag” ]; then
printf “Option -a specifiedn”
fi
if [ ! -z “$bflag” ]; then
printf ‘Option -b “%s” specifiedn’ “$bval”
fi
shift $(($OPTIND – 1))
printf “Remaining arguments are: %sn$*”
RATIONALE
The getopts utility was chosen in preference to the System V getopt utility because getopts handles option-arguments containing
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
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 — %cn”, <program name>, <option character>
“%s: option requires an argument — %cn”, <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 .