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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 bash
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.

The Instructions
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:

Flag variable (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’.

Value variable (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
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 eval 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
-p|--path->PATH:' $*
eval $retval

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


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

PATH=(/usr /bin)

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