parse utility options
/usr/bin/getopts optstring name [arg ...]
This shell script executes the builtin command of the same name as
implemented by the
for more information on this shell.
utility can be used to retrieve options and option-arguments
from a list of parameters.
Each time it is invoked, the
utility places the value of the next option in the shell
variable specified by the
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, the
utility will 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 will be unset.
If an option character not contained in the
operand is found where an option character is expected,
the shell variable specified by
will be set to the question-mark (?) character.
In this case, if the first character in
is a colon (:), the shell variable OPTARG is set to the option
character found, but no output will be written to standard
error; otherwise, the shell variable OPTARG is unset and a
diagnostic message will be 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
If an option-argument is missing:
If the first character of
is a colon, the shell variable specified by
is set to the colon (:) character and the shell variable OPTARG
is set to the option character found.
Otherwise, the shell variable specified by
is set to the question-mark character, 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
processing; a diagnostic message will be written as stated,
but the exit status will be zero.
When the end of options is encountered, the
utility will exit with a return value greater than zero; the shell variable
OPTIND is set to the index of the first non-option-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 non-option-arguments; the
variable is set to the question-mark character.
Any of the following identifies the end of options:
the special option -- (two dashes with no space)
finding an argument that does not begin with a - (dash)
encountering an error
The shell variables OPTIND and OPTARG are local to the caller of
and are not exported by default.
The shell variable specified by the
operand, OPTIND and OPTARG affect the current shell execution
If the application sets OPTIND to the value 1, a new set of
parameters can be used: either the current positional parameters or new
Any other attempt to invoke
multiple times in a single shell execution environment with parameters
(positional parameters or
operands) that are not the same in all invocations, or with an
OPTIND value modified to be a value other than 1,
produces an error.
The following operands are supported:
A string containing the option characters recognised by the utility invoking
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
interprets 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
The characters question mark (?) and colon (:) must not be used as option
characters by an application.
If the option-argument is not supplied as a separate argument
from the option character, the value in OPTARG
is stripped of the option character and the dash (-).
The first character in
behaves if an option character is not known or an option-argument
The name of a shell variable that will be set by the
utility to the option character that was found.
utility by default parses positional parameters passed to the
invoking shell procedure.
parameters are given, they will be parsed instead of the positional
The following environment variables affect the execution of
Provide a default value for the internationalization variables
that are unset or null.
If LANG is unset or null, the corresponding value from the
implementation-specific default locale will be used.
If any of the internationalisation variables contains an invalid
setting, the utility will behave as if none of the variables
had been defined.
If set to a non-empty string value, override the values of all
the other internationalization variables.
Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single- as opposed to multi-byte
characters in arguments and input files).
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error.
This variable will be used by the
utility as the index of the next argument to be processed.
Whenever an error is detected and the first character in the
operand is not a colon (:), a diagnostic message will be written
to standard error with the following information in an unspecified format:
The invoking program name will be identified in the message.
The invoking program name will be the value of the shell special
parameter $0 at the time the
utility is invoked.
A name equivalent to:
If an option is found that was not specified in
this error will be identified and the invalid option character is
identified in the message.
If an option requiring an option-argument is found, but an
option-argument is not found, this error is identified and the
invalid option character is identified in the message.
affects the current shell execution environment, it is generally
provided as a shell regular built-in.
If it is called in a subshell or
separate utility execution environment, such as one of the following:
(getopts abc value "$@")
nohup getopts ...
find . -exec getopts ... ;
it will 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 want to use
to parse their arguments will usually want to save the value of
OPTIND on entry and restore it before returning.
However, there will be cases when a function will want to change
OPTIND for the calling shell.
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" "$*"
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UnixWare 7 Release 7.1.4 - 25 April 2004