Originální popis anglicky:
getopts - parse utility options
Návod, kniha: POSIX Programmer's Manual
getopts 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
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.
None.
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 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.
Not used.
None.
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.
Default.
Not used.
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:
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.
None.
None.
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.
Default.
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 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.
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:
"%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
character found in error.
None.
Special Parameters , the System Interfaces volume of
IEEE Std 1003.1-2001,
getopt()
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
.
