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 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 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 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.
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 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.
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 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.
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 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.
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:
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>s.
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:
Historical shells with built-in versions of getopt() or getopts
have used
different formats, frequently not even indicating the option character
found in error.
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
GETOPTS (P)
2003
Generated by OpenAsthra.com from man1p/getopts.1p using man macros.
