GETOPTS(1P) POSIX Programmer's Manual GETOPTS(1P)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.
NAMEgetopts — parse utility options
SYNOPSISgetopts 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
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 out‐
put 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 applica‐
tion, 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 vari‐
able specified by name shall be set to the <colon> character and
the shell variable OPTARG shall be set to the option character
* 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 val‐
ues. 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
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 charac‐
ters 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 pro‐
duces unspecified results. If the option-argument is not sup‐
plied 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.
The following environment variables shall affect the execution of
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard
NLSPATH Determine the location of message catalogs for the processing
OPTIND This variable shall be used by the getopts utility as the
index of the next argument to be processed.
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 for‐
* 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:
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 iden‐
tified 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.
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
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
(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
The following example script parses and displays its arguments:
while getopts ab: name
case $name in
?) printf "Usage: %s: [−a] [−b value] args\n" $0
if [ ! −z "$aflag" ]; then
printf "Option −a specified\n"
if [ ! −z "$bflag" ]; then
printf 'Option −b "%s" specified\n' "$bval"
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>
The OPTARG variable is not mentioned in the ENVIRONMENT VARIABLES sec‐
tion 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 op‐
erand, it disables diagnostics concerning missing option-arguments and
unexpected option characters. This replaces the use of the OPTERR vari‐
able 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 implementa‐
tions with superior (``friendlier'') formats objected to the formats
used by some historical implementations. The standard developers con‐
sidered it important that the information in the messages used be uni‐
form 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>, \
Historical shells with built-in versions of getopt() or getopts have
used different formats, frequently not even indicating the option char‐
acter found in error.
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()COPYRIGHT
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 Electri‐
cal 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 .
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IEEE/The Open Group 2013 GETOPTS(1P)