DOKK / manpages / debian 11 / libbash / getopt_long.1.en
GETOPTS(3) 3 (libbash getopts library manual) GETOPTS(3)

getopts — libbash library for command line parameters parsing

$retval getopt_long ⟨Instructions⟩ ⟨Parameters⟩

This is a documentation for libbash getopts library, that implements getopt_long function for bash(1). For documentation of bash getopts function, please see getopts(1) ( getopts(1posix) on some systems).

Here is a table for reference:

getopts(1)
(or 1posix on some systems) implemented by
getopts(3)
implemented by libbash.
getopt(1)
implemented by getopt utils (part of util-linux)
getopt_long(1)
implemented by libbash and installed to section 1 instead of 3 to prevent collision with C man pages.
getopt(3)
implemented by GNU C library.
getopt_long(3)
implemented by GNU C library.
I have also seen separate getopt utility which part of util-linux package.

The getopt_long function parses the command line arguments. It uses Instructions as the rules for parsing the Parameters.

A string that specifies rules for parameters parsing. The instructions string is built of a group of independent instructions, separated by a white space. Each instruction must have the following structure:

This structure contains three parts:

This is the parameter single-letter sign. For example -h.
This is the parameter's corresponding multi-letter sign. For example --help.
This is the name of the variable that will contain the parameter value. For example: .

The Variable name can represent one of two variables types:

(not followed by ‘:’)
In this case, it will hold the value 1 if ‘on’ (i.e. was specified on command line) and will not be defined if ‘off’.
(followed by ‘:’)
In this case, the value it will hold is the string that was given as the next parameter in the Parameters string (Separated by white-space or ‘=’ ). If input contains more then one instance of the considered command line option, an array of the given parameters will be set as the value of the variable.

The Parameters are simply the parameters you wish to parse.

This function returns a string that contains a set of variables definitions. In order to define the variables, this string should be given as a parameter to function. This value is returned in the variable $retval.

Parse command line parameters looking for the flags -h | --help and -v | --version and for the value -p | --path :

getopt_long '-h|--help->HELP
              -v|--version->VERSION
              -p|--path->PATH:' $*
eval $retval

In this example, for the parameters --help --path=/usr/ the variables that will be created are:

HELP=1
PATH=/usr/

for the parameters --help --path=/usr --path=/bin the variables that will be created are:

HELP=1
PATH=(/usr /bin)

Values must not contain the string `__getopts__'. This string will be parsed as a single white-space.

A value should not start with an already defined multi-letter sign. If such a value exists, it will be treated as the equivalent singe-letter sign. This bug only accures when using a single-letter sign, or a multi-letter sign that are not followed by a `='.

For example: If we have a script named `foo', and we parse the parameters `-d|--dir:' and `-f|--file:', then

foo -d --file
and 
foo --dir --file
will not work 
foo --dir=--file
will work.

Hai Zaar ⟨haizaar@haizaar.com⟩
Gil Ran ⟨gil@ran4.net⟩

ldbash(1), getopt_long(1), getopts(1), getopt(1), libbash(1), getopt(3), getopt_long(3)

Linux