The getopts utility can be used to retrieve options and option-arguments from a list of parameters.
Each time it is invoked, the getopts utility 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 will be initialised to 1.
When the option requires an option-argument, the getopts 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 optstring operand is found where an option character is expected, the shell variable specified by name will be set to the question-mark ( ? ) character. In this case, if the first character in optstring is a colon (:, the shell variable OPTARG will be set to the option character found, but no output will be written to standard error; otherwise, the shell variable OPTARG will be 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 getopts processing.
If an option-argument is missing:
If the first character of optstring is a colon, the shell variable specified by name will be set to the colon character and the shell variable OPTARG will be set to the option character found.
Otherwise, the shell variable specified by name will be set to the question-mark character (?), the shell variable OPTARG will be 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 getopts processing; a diagnostic message will be written as stated, but the exit status will be zero.
When the end of options is encountered, the getopts utility will exit with a return value greater than zero; the shell variable OPTIND will 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 will be set to the question-mark 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.
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.
getopts is a built-in Bourne shell command used to parse positional parameters and to check for valid options. See sh(1). It supports all applicable rules of the command syntax standard (see Rules 3-10, intro(1)). It should be used in place of the getopt command.
optstring must contain the option letters the command using getopts will recognize; if a letter is followed by a colon, the option is expected to have an argument, or group of arguments, which must be separated from it by white space.
Each time it is invoked, getopts places the next option in the shell variable name and the index of the next argument to be processed in the shell variable OPTIND. Whenever the shell or a shell script is invoked, OPTIND is initialized to 1.
When an option requires an option-argument, getopts places it in the shell variable OPTARG.
If an illegal option is encountered, ? will be placed in name.
When the end of options is encountered, getopts exits with a non-zero exit status. The special option – may be used to delimit the end of the options.
By default, getopts parses the positional parameters. If extra arguments (argument . . .) are given on the getopts command line, getopts parses them instead.
/usr/lib/getoptcvt reads the shell script in filename, converts it to use getopts instead of getopt, and writes the results on the standard output.
So that all new commands will adhere to the command syntax standard described in intro(1), they should use getopts or getopt to parse positional parameters and check for options that are valid for that command.
getopts prints an error message on the standard error when it encounters an option letter not included in optstring.
Although the following command syntax rule (see intro(1)) relaxations are permitted under the current implementation, they should not be used because they may not be supported in future releases of the system. As in the EXAMPLES section below, -a and -b are options, and the option -o requires an option-argument.
The following example violates Rule 5: options with option-arguments must not be grouped with other options:
example% cmd -aboxxx filename
The following example violates Rule 6: there must be white space after an option that takes an option-argument:
example% cmd -ab oxxx filename
Changing the value of the shell variable OPTIND or parsing different sets of arguments may lead to unexpected results.
Checks arg for legal options. If arg is omitted, the positional parameters are used. An option argument begins with a + or a -. An option not beginning with + or - or the argument – ends the options. optstring contains the letters that getopts recognizes. If a letter is followed by a :, that option is expected to have an argument. The options can be separated from the argument by blanks.
getopts places the next option letter it finds inside variable name each time it is invoked with a + prepended when arg begins with a +. The index of the next arg is stored in OPTIND. The option argument, if any, gets stored in OPTARG.
A leading : in optstring causes getopts to store the letter of an invalid option in OPTARG, and to set name to ? for an unknown option and to : when a required option is missing. Otherwise, getopts prints an error message. The exit status is non-zero when there are no more options.
For a further discussion of the Korn shell's getopts built-in command, see the previous discussion in the Bourne shell (sh) section of this manpage.
The following operands are supported:
A string containing the option characters recognised 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; see getopt(3C). 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.
The name of a shell variable that will be set by the getopts utility to the option character that was found.
The getopts utility by default will parse positional parameters passed to the invoking shell procedure. If args are given, they will be parsed instead of the positional parameters.
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 will not affect the shell variables in the caller's environment.
Notice that shell functions share OPTIND with the calling shell even though the positional parameters are changed. Functions that want to use getopts 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:
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 following fragment of a shell program shows how one might process the arguments for a command that can take the options -a or -b, as well as the option -o, which requires an option-argument:
while getopts abo: c do case $c in a | b) FLAG=$c;; o) OARG=$OPTARG;; \?) echo $USAGE exit 2;; esac done shift `expr $OPTIND - 1`
This code accepts any of the following as equivalent:
cmd -a -b -o "xxx z yy" filename cmd -a -b -o "xxx z yy" -- filename cmd -ab -o xxx,z,yy filename cmd -ab -o "xxx z yy" filename cmd -o xxx,z,yy -b -a filename
See environ(5) for descriptions of the following environment variables that affect the execution of getopts: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.
This variable is used by getopts as the index of the next argument to be processed.
This variable is used by getopts to store the argument if an option is using arguments.
The following exit values are returned:
An option, specified or unspecified by optstring, was found.
The end of options was encountered or an error occurred.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
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 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 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 message.