GETOPTS(P) POSIX Programmer's Manual GETOPTS(P)
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
IEEE Std 1003.1-2001, 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 vari-
able 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 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 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 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 name variable shall be set to
the question-mark character. Any of the following shall identify 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 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 Shell Execu-
tion 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
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 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 argu-
ments, 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 IEEE Std 1003.1-2001.) 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.
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
IEEE Std 1003.1-2001, 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 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 colon ( ':' ), a diagnostic message shall be written
to standard error with the following information in an unspecified for-
mat:
* The invoking program name shall be identified in the message. The
invoking program name shall be the value of the shell special param-
eter 0 (see Special Parameters ) at the time the getopts utility is
invoked. A name equivalent to:
basename "$0"
may be used.
* If an option is found that was not specified in optstring, this
error is identified and the invalid option character shall be iden-
tified in the message.
* If an option requiring an option-argument is found, but an option-
argument is not found, this error shall be identified and the
invalid option character shall be identified in the message.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 An option, specified or unspecified by optstring, was found.
>0 The end of options was encountered or an error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
Since getopts affects the current shell execution environment, it is
generally provided as a shell regular built-in. If it is called in a
subshell or separate utility execution environment, such as one of the
following:
(getopts abc value "$@")
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] 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" "$*"
RATIONALE
The getopts utility was chosen in preference to the System V getopt
utility because getopts handles option-arguments containing <blank>s.
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>, \
<option character>
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.
FUTURE DIRECTIONS
None.
SEE ALSO
Special Parameters , the System Interfaces volume of
IEEE Std 1003.1-2001, getopt()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 GETOPTS(P)
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