options.bash and options.zsh
by David Vilar
This is a small library for handling command line options in bash and zsh. It is
inspired by the optparse python library. An example usage is
addOption -n --number required help="Specify some number" dest=myNumber
addOption -a --aux flagTrue help="Another option, but without dest"
addOption -o help="Option with default" default="a b" dest=otherO
parseOptions "$@"
This example defines the options -n/--number, -a/--aux and -o. -n sets the
variable $myNumber and is required by the script to run. -a sets the $aux
variable to true when given (it does not require arguments). -o sets the
variable $otherO, but if not specified on the command line, it defaults to "a b".
Additionaly the option -h/--help is automatically generated and produces this
output:
usage: example.bash [options]
Options:
-n,--number Specify some number
-a,--aux Another option, but without dest
-o Option with default
-h,--help Show this help message
To use the library in your own script, copy it somewhere and include it in your
script (.bash or .zsh depending on which shell you use):
. options.bash
New options are added with the addOption command. It scans its arguments for
those beginning with a dash to get the short and long option syntax (one of them
can be omitted). Additionally you can give these additional commands:
+ dest=VAR
Sets the destination of the variable. If not given, it defaults to
the long option name (see option --aux in the example above)
+ action=COMMAND
Calls command if the option is specified in the command line (usually this is
used for calling functions in the script, but it is not limited to it)
+ default=VALUE
Sets the default value for the option, if not given in the command line
+ required
Specifies that the option is required [I know, this is a contradiction of
terms ;-)]. The script will abort with an error message if the option is not
given in the command line
+ help=MESSAGE
Specifies the help message to be written in the output with the -h options
+ flagTrue/flagFalse
Specifies that the option is a boolean. flagTrue sets the default value to
false and turns it to true if the option is given in the command line. flagFalse
works the other way round. Note that you can use such variable directly in bash
constructs like if clauses, while loops, etc:
if $var; then
echo "var is set
fi
+ configFile
This option makes the script read an external file. Normally this is used as a
config file, where the values of variables are set, e.g.
input=file.in
output=file.out
iterations=3
Note that the file is included directly in bash, no fancy parsing is done.
This means among other things that no whitespace is allowed around = signs and
that command can be executed from within the "config file". Use with caution.
+ dontShow
Do not show the option in the output of -h. Useful if some options are thought
to be used only when calling the script from other script.
Once you have defined the options for your script, use the command
parseOptions "$@"
to parse the command line and set the appropriate variables. Additional command
line arguments are stored in the $optArgv[] array, with $optArgc storing the
number of actual arguments.
The library follows the usual convention of supporting -- to separate options
from command line arguments, e.g. in the call
./example.sh -n 3 -a -- -b aaa
the arguments are "-b" and "aaa".
This library has been extensively used in the Jane statistical machine
translation toolkit (http://www.hltpr.rwth-aachen.de/jane)