GetoptLong

The GetoptLong class allows you to parse command line options similarly to the GNU getopt_long() C library call. Note, however, that GetoptLong is a pure Ruby implementation.

GetoptLong allows for POSIX-style options like --file as well as single letter options like -f

The empty option -- (two minus symbols) is used to end option processing. This can be particularly important if options have optional arguments.

Here is a simple example of usage:

require 'getoptlong'
opts = GetoptLong .new (
 [ '--help', '-h', GetoptLong ::NO_ARGUMENT ],
 [ '--repeat', '-n', GetoptLong ::REQUIRED_ARGUMENT ],
 [ '--name', GetoptLong ::OPTIONAL_ARGUMENT ]
)
dir = nil
name = nil
repetitions = 1
opts.each  do |opt, arg|
 case opt
 when '--help'
 puts <<-EOF
hello [OPTION] ... DIR
-h, --help:
 show help
--repeat x, -n x:
 repeat x times
--name [name]:
 greet user by name, if name not supplied default is John
DIR: The directory in which to issue the greeting.
 EOF
 when '--repeat'
 repetitions = arg.to_i
 when '--name'
 if arg == ''
 name = 'John'
 else
 name = arg
 end
 end
end
if ARGV.length != 1
 puts "Missing dir argument (try --help)"
 exit 0
end
dir = ARGV.shift
Dir .chdir(dir)
for i in (1..repetitions)
 print "Hello"
 if name
 print ", #{name}"
 end
 puts
end

Example command line:

hello -n 6 --name -- /tmp

Related methods