getopts - parse utility (command) options
getopts optstring name [arg ...]
getopts is used to retrieve options and option-arguments from a list
Each time it is invoked, getopts places 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 is initialized to 1.
When the option requires an option-argument, getopts places 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 is 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 is set to the question-mark (?) character. In this case, if the
first character in optstring is a colon (:), the shell variable OPTARG
is set to the option character found, but no output is written to
standard error; otherwise, the shell variable OPTARG is unset and a
diagnostic message is written to standard error. This condition is
considered to be an error detected in the way arguments were presented
to the invoking application, but is not an error in getopts
If an option-argument is missing:
+ If the first character of optstring is a colon, the shell
variable specified by name is set to the colon character and
the shell variable OPTARG is set to the option character
+ Otherwise, the shell variable specified by name is set to the
question-mark character, the shell variable OPTARG is unset,
and a diagnostic message is written to the standard error.
This condition is considered to be an error detected in the
way arguments are presented to the invoking application, but
is not an error in getopts processing; a diagnostic message is
written as stated, but the exit status is zero.
When the end of options is encountered, getopts exits with a return
value greater than zero. The shell variable OPTIND is set to the
index of the first nonoption-argument, where the first -- argument is
considered to be an option argument if there are no other non-option
arguments appearing before it, or the value $# + 1 if there are no
nonoption-arguments; the name variable is set to the question-mark
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character. Any of the following identifies the end of options: the
special option --, finding an argument that does not begin with a -,
or encountering an error.
The shell variables OPTIND and OPTARG are local to the caller of
getopts and are not exported by default.
The shell variable specified by the name operand, OPTIND, and OPTARG
affect the current shell execution environment.
The following operands are supported:
optstring A string containing the option characters
recognized by the utility invoking getopts. If a
character is followed by a colon (:), the option
will 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
will 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 recognised if it is
not supplied as a separate argument when getopts
is invoked. The characters question-mark (?) and
colon (:) must 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 will be stripped of the option
character and the -. The first character in
optstring will determine how getopts will behave
if an option character is not known or an option-
argument is missing.
name The name of a shell variable that is set by
getopts to the option character that was found.
getopts by default parses positional parameters passed to the invoking
shell procedures. If args are given, they are parsed instead of the
The following environment variable affects the execution of the
OPTIND Used by getopts as the index of the next argument
to be processed.
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Whenever an error is detected and the first character in the optstring
operand is not a colon (:), a diagnostic message will be written to
standard error with the following information in an unspecified
+ The invoking program name will be identified in the message.
The invoking program name will be the value of the shell
special parameter 0 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 will be identified and the invalid option character
will be identified in the message.
+ If an option requiring an option-argument is found, but an
option-argument is not found, this error will be identified
and the invalid option character will be identified in the
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. Functions that use
getopts to parse their arguments should save the value of OPTIND on
entry and restore it before returning. However, there will be cases
when a function must change OPTIND for the calling shell.
The following example script parses and displays its arguments:
while getopts ab: name
case $name in
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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" "$*"
getopt(1), ksh(1), sh-posix(1), sh(1), getopt(3C).
getopts: XPG4, POSIX.2
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