Command line argument parsing for simple applications.
Clap is a small library that can be bundled with your command line application. It covers the simple case of executing code based on the flags or parameters passed, and it does so with just under 30 lines of code.
Using Clap is simple: just pass ARGV
and a hash of flags, and it will extract
the arguments as needed.
Clap.run ARGV,
"-a" => lambda { |param| ... },
"-b" => lambda { ... }
To better illustrate the usage, in the following examples ARGV
is replaced by
an array of strings.
If you want your command line application to require a file or display a version number, you can configure it like this:
Clap.run %w(-r foo -v),
"-r" => lambda { |file| require file },
"-v" => lambda { puts VERSION }
This will detect the -r
or -v
flags and act accordingly. Note that it will
also read the necessary number of parameters for each flag based on the arity
of the passed lambda.
Another example, for an application that takes a -v
flag and also a list of
files:
files = Clap.run %w(-v foo bar),
"-v" => lambda { puts VERSION }
files == %w(foo bar)
If you are in doubt, check the tests for the different use cases.
When using Clap.run, you must use an empty set of arguments instead of leaving out the arguments entirely:
files = Clap.run ARGV,
"-a" => lambda {|| ... }
Otherwise Clap will throw an error regarding "negative array size" for the arity of your lambdas.
$ gem install clap
Copyright (c) 2010 Michel Martens
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