Content-type: text/html Man page of getopts

getopts

Section: User Commands (1)
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NAME

getopts - Parses utility options  

SYNOPSIS

getopts optstring name [arg...]


 

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

getopts: XPG4, XPG4-UNIX

Refer to the standards(5) reference page for more information about industry standards and associated tags.
 

OPTIONS

None
 

OPERANDS

A string containing the option characters recognized by the utility invoking getopts. If a character is followed by a colon (:), the option is 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 interprets the characters following an option character requiring arguments as an argument whether or not this is done. An explicit null option-argument is not recognized if it is not supplied as a separate argument when getopts is invoked. 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 is stripped of the option character and the hyphen (-). The first character in optstring determines getopts behavior if an option character is not known or an option-argument is missing. The name of a shell variable that is set by the getopts utility to the option character that was found.

The getopts utility by default parses positional parameters passed to the invoking shell procedure. If args are given, they are parsed instead of the positional parameters.
 

DESCRIPTION

The getopts utility is used to retrieve flags and flag arguments from a list of parameters.

Each time it is invoked, the getopts utility places the value of the next flag 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 is initialized to 1.

When the flag requires a flag argument, the getopts utility places it in the shell variable OPTARG. If no flag is found, or if the flag found does not have a flag argument, OPTARG is unset.

If a flag character not contained in the optstring operand is found where a flag character is expected, the shell variable specified by name is set to the question-mark (?) character. In this case, if the first character in optstring is a colon (:), the shell variable OPTARG is set to the flag character found, but no output is written; otherwise, the shell variable OPTARG is unset and a diagnostic message written. 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 a flag argument is missing, then: If the first character of optstring is a colon, the shell variable specified by name is set to the colon (:) character and the shell variable OPTARG is set to the flag character found. Otherwise, the shell variable specified by name 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 getopts processing; a diagnostic message is written as stated, but the exit status is zero.

When the end of flags is encountered the getopts utility exits with: A return value greater than zero The shell variable OPTIND set to the index of the first nonflag argument, where the first -- argument is considered to be a flag argument if there are no other nonflag arguments appearing before it, or the value $# + 1 if there are no nonflag arguments The name variable set to the question-mark (?) character

Any of the following identifies the end of flags: The special flag -- Finding an argument that does not begin with a - 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 flag 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.
 

NOTES

If getopts is called in a subshell or separate utility execution environment, such as one of the following it will not affect the shell variables in the caller's environment:

(getopts abc value "$@") nohup getopts ... 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 are cases when a function will want to change OPTIND for the calling shell.
 

RESTRICTIONS

The getopts command is implemented as a shell built-in command. It is only available to users of the Korn (ksh) and POSIX shells.

A similar capability is available to Bourne and C shell users with the getopt command.
 

EXIT STATUS

The following exit values are returned: An option, specified or unspecified by optstring, was found. Successful completion. The end of options was encountered or an error occurred.
 

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" "$*"


 

ENVIRONMENT VARIABLES

The following environment variables affect the execution of getopts: Provides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization variables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, overrides the values of all the other internationalization variables. Determines the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multibyte characters in arguments and input files). Determines the locale used to affect the format and contents of diagnostic messages written to standard error. Determines the location of message catalogues for the processing of LC_MESSAGES. On exit, this variable will contain the value of a flag argument if one was found, otherwise it is unset. This variable is used by the getopts utility as the index of the next argument to be processed.
 

SEE ALSO

Commands:  getopt(1), ksh(1), sh(1p)

Routines:  getopt(3)

Standards:  standards(5)


 

Index

NAME
SYNOPSIS
STANDARDS
OPTIONS
OPERANDS
DESCRIPTION
NOTES
RESTRICTIONS
EXIT STATUS
EXAMPLES
ENVIRONMENT VARIABLES
SEE ALSO

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Time: 02:42:46 GMT, October 02, 2010