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 =
  [ '--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.
    when '--repeat'
      repetitions = arg.to_i
    when '--name'
      if arg == ''
        name = 'John'
        name = arg

if ARGV.length != 1
  puts "Missing dir argument (try --help)"
  exit 0

dir = ARGV.shift

for i in (1..repetitions)
  print "Hello"
  if name
    print ", #{name}"

Example command line:

hello -n 6 --name -- /tmp


Argument flags.

No documentation available

Return ordering.

Read & Write

Set/Unset ‘quiet’ mode.

Read & Write

Set/Unset ‘quiet’ mode.


Examine whether an option processing is failed.


Examine whether an option processing is failed.

Class Methods

Set up option processing.

The options to support are passed to new() as an array of arrays. Each sub-array contains any number of String option names which carry the same meaning, and one of the following flags:


Option does not take an argument.


Option always takes an argument.


Option may or may not take an argument.

The first option name is considered to be the preferred (canonical) name. Other than that, the elements of each sub-array can be in any order.

Instance Methods

Iterator version of ‘get’.

The block is called repeatedly with two arguments: The first is the option name. The second is the argument which followed it (if any). Example: (‘–opt’, ‘value’)

The option name is always converted to the first (preferred) name given in the original options to

An alias for each

Return the appropriate error message in POSIX-defined format. If no error has occurred, returns nil.

Get next option name and its argument, as an Array of two elements.

The option name is always converted to the first (preferred) name given in the original options to

Example: [‘–option’, ‘value’]

Returns nil if the processing is complete (as determined by STATUS_TERMINATED).

An alias for get

Set the handling of the ordering of options and arguments. A RuntimeError is raised if option processing has already started.

The supplied value must be a member of GetoptLong::ORDERINGS. It alters the processing of options as follows:


Options are required to occur before non-options.

Processing of options ends as soon as a word is encountered that has not been preceded by an appropriate option flag.

For example, if -a and -b are options which do not take arguments, parsing command line arguments of ‘-a one -b two’ would result in ‘one’, ‘-b’, ‘two’ being left in ARGV, and only (‘-a’, ”) being processed as an option/arg pair.

This is the default ordering, if the environment variable POSIXLY_CORRECT is set. (This is for compatibility with GNU getopt_long.)


Options can occur anywhere in the command line parsed. This is the default behavior.

Every sequence of words which can be interpreted as an option (with or without argument) is treated as an option; non-option words are skipped.

For example, if -a does not require an argument and -b optionally takes an argument, parsing ‘-a one -b two three’ would result in (‘-a’,”) and (‘-b’, ‘two’) being processed as option/arg pairs, and ‘one’,‘three’ being left in ARGV.

If the ordering is set to PERMUTE but the environment variable POSIXLY_CORRECT is set, REQUIRE_ORDER is used instead. This is for compatibility with GNU getopt_long.


All words on the command line are processed as options. Words not preceded by a short or long option flag are passed as arguments with an option of ” (empty string).

For example, if -a requires an argument but -b does not, a command line of ‘-a one -b two three’ would result in option/arg pairs of (‘-a’, ‘one’) (‘-b’, ”), (”, ‘two’), (”, ‘three’) being processed.

Set an error (a protected method).

Set options. Takes the same argument as

Raises a RuntimeError if option processing has already started.

Explicitly terminate option processing.

Returns true if option processing has terminated, false otherwise.