ruby-ucl

Ruby bindings to the libucl library for parsing configuration files written in the Universal Configuration Language (UCL).

UCL is a configuration format inspired by nginx and JSON. It is a superset of JSON, so any valid JSON document is also valid UCL, while adding a more relaxed, human-friendly syntax (unquoted keys, comments, optional commas, multipliers, macros, …).

Parsed configurations are returned as plain Ruby objects (Hash, Array, String, Integer, Float, true/false, nil), so no special object model has to be learned.

gem install ucl

Or add it to your Gemfile:

gem 'ucl'

The extension binds to the native libucl library (version 0.8.2 or later). At build time it is located as follows:

1. If a system-wide libucl is found (via pkg-config, or under /opt or /usr/local), it is used.
2. Otherwise libucl is downloaded and compiled from source automatically (using mini_portile2 and CMake). This requires cmake and a C compiler to be available.

You can force the source build regardless of any system installation:

gem install ucl -- --enable-vendor-libucl
# or, with Bundler:
bundle config set build.ucl --enable-vendor-libucl

Debian/Ubuntu note: do not apt install libucl-dev. That package is an unrelated UCL data-compression library that merely shares the name — it does not provide ucl_parser_new. Since the configuration parser is not packaged for Debian, just install cmake and a compiler and let the gem build libucl from source. (The parser is packaged on Fedora, Homebrew and FreeBSD ports as libucl.)

require 'ucl'

# Parse a string of UCL data
UCL.parse(File.read('foo.conf'))

# Parse a file directly (enables file-relative variables such as $FILENAME)
UCL.load_file('foo.conf')

# Pass flags explicitly (combine them with a bitwise OR)
UCL.load_file('foo.conf', UCL::KEY_SYMBOL | UCL::KEY_LOWERCASE)

# Or set the default flags applied to every subsequent call
UCL.flags = UCL::KEY_SYMBOL
UCL.parse('name = value')          #=> { :name => "value" }

Both parse and load_file accept an optional flags argument. When it is omitted, the value of UCL.flags (default: no flag) is used.

On a malformed configuration, or if conversion of the parsed tree fails, a UCL::Error is raised.

Given a configuration like:

# a sample configuration
name = example
timeout = 30s            # parsed as a number of seconds
max_size = 10mb          # size multipliers are understood

servers = [
    { host = a.example, port = 8080 },
    { host = b.example, port = 8081 },
]

logging {
    level = info
    enabled = yes
}

UCL.load_file returns:

{
  "name"     => "example",
  "timeout"  => 30.0,
  "max_size" => 10485760,
  "servers"  => [ { "host" => "a.example", "port" => 8080 },
                  { "host" => "b.example", "port" => 8081 } ],
  "logging"  => { "level" => "info", "enabled" => true },
}

Notes:

• The parser uses explicit (not implicit) arrays, so a key repeated several times is collected into an Array of its values:

  UCL.parse("a = 1\na = 2")   #=> { "a" => [1, 2] }
  UCL.parse("a = 1")          #=> { "a" => 1 }

• Integers understand size multipliers (1k → 1000, 1kb → 1024, 1mb → 1048576), hexadecimal (0x1f → 31) and JSON is accepted as-is.

• Returned strings carry their verbatim bytes but are tagged with the ASCII-8BIT (binary) encoding; call String#force_encoding('UTF-8') if you need them as UTF-8.

bundle install          # install development dependencies
rake compile            # build the C extension into ext/
rake test               # compile and run the test suite
rake clobber            # remove all generated files

rake test works with the development gems installed system-wide too; with a Gemfile.lock present, prefix commands with bundle exec.

Released under the MIT License. See LICENSE.