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GETOPTS(1P) POSIX Programmer's Manual GETOPTS(1P)
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.
getopts — parse utility options
getopts optstring name [arg...]
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.
None.
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.
Not used.
None.
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.
Default.
Not used.
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 "$0"
may be used.
* If an option is found that was not specified in optstring, this
error is identified and the invalid option character shall be
identified in the message.
* If an option requiring an option-argument is found, but an
option-argument is not found, this error shall be identified and
the invalid option character shall be identified in the message.
None.
None.
The following exit values shall be returned:
0 An option, specified or unspecified by optstring, was found.
>0 The end of options was encountered or an error occurred.
Default.
The following sections are informative.
Since getopts affects the current shell execution environment, it is
generally provided as a shell regular built-in. If it is called in a
subshell or separate utility execution environment, such as one of
the following:
(getopts abc value "$@")
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.
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$*"
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.
None.
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)
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)
Pages that refer to this page: pax(1p), getopt(3p)