Sometimes Ruby apps shell out to command-line executables, but there is no standard way to ensure those underlying dependencies are met. Users usually find out via a nasty stack-trace and whatever wasn't captured on stderr, or by the odd behavior exposed by a version mismatch.

Cliver is a simple gem that provides an easy way to detect and use command-line dependencies. Under the covers, it uses rubygems/requirements so it supports the version requirements you're used to providing in your gemspec.


Detect and Detect!

The detect methods search your entire path until they find a matching executable or run out of places to look.

# no version requirements
# => '/Users/yaauie/.bin/subl'

# one version requirement
Cliver.detect('bzip2', '~> 1.0.6')
# => '/usr/bin/bzip2'

# many version requirements
Cliver.detect('racc', '>= 1.0', '< 1.4.9')
# => '/Users/yaauie/.rbenv/versions/1.9.3-p194/bin/racc'

# dependency not met
Cliver.detect('racc', '~> 10.4.9')
# => nil

# detect! raises Cliver::Dependency::NotMet exceptions when the dependency
# cannot be met.
Cliver.detect!('ruby', '1.8.5')
#  Cliver::Dependency::VersionMismatch
#    Could not find an executable ruby that matched the
#    requirements '1.8.5'. Found versions were {'/usr/bin/ruby'=> '1.8.7'}
#  Cliver::Dependency::NotFound
#    Could not find an executable asdfasdf on your path


The assert method is useful when you do not have control over how the dependency is shelled-out to and require that the first matching executable on your path satisfies your version requirements. It is the equivalent of the detect! method with strict: true option.

Advanced Usage:

Version Detectors

Some programs don't provide nice 'version 1.2.3' strings in their --version output; Cliver lets you provide your own version detector with a pattern.

Cliver.assert('python', '~> 1.7',
              detector: /(?<=Python )[0-9][.0-9a-z]+/)

Other programs don't provide a standard --version; Cliver::Detector also allows you to provide your own arg to get the version:

# single-argument command
Cliver.assert('janky', '~> 10.1.alpha',
              detector: '--release-version')

# multi-argument command
Cliver.detect('ruby', '~> 1.8.7',
              detector: [['-e', 'puts RUBY_VERSION']])

You can use both custom pattern and custom command by supplying an array:

Cliver.assert('janky', '~> 10.1.alpha',
              detector: ['--release-version', /.*/])

And even supply multiple arguments in an Array, too:

# multi-argument command
Cliver.detect('ruby', '~> 1.8.7',
              detector: ['-e', 'puts RUBY_VERSION'])

Alternatively, you can supply your own detector (anything that responds to #to_proc) in the options hash or as a block, so long as it returns a Gem::Version-parsable version number; if it returns nil or false when version requirements are given, a descriptive ArgumentError is raised.

Cliver.assert('oddball', '~> 10.1.alpha') do |oddball_path|'../VERSION', oddball_path)).chomp

And since some programs don't always spit out nice semver-friendly version numbers at all, a filter proc can be supplied to clean it up. Note how the filter is applied to both your requirements and the executable's output:


Cliver.assert('built-thing', '~> 2013.4r8273',
              filter: proc { |ver|'r','.') })

Since Cliver uses Gem::Requirement for version comparrisons, it obeys all the same rules including pre-release semantics.

Search Path

By default, Cliver uses ENV['PATH'] as its search path, but you can provide your own. If the asterisk symbol (*) is included in your string, it is replaced ENV['PATH'].

Cliver.detect('gadget', path: './bins/:*')
# => 'Users/yaauie/src/project-a/bins/gadget'

Supported Platforms

The goal is to have full support for all platforms running ruby >= 1.9.2, including rubinius and jruby implementations, as well as basic support for legacy ruby 1.8.7. Windows has support in the codebase, but is not available as a build target in [travis_ci][].

See Also: