module RbConfig

The module storing Ruby interpreter configurations on building.

This file was created by mkconfig.rb when ruby was built. It contains build information for ruby which is used e.g. by mkmf to build compatible native extensions. Any changes made to this file will be lost the next time ruby is built.

Constants

CONFIG

The hash configurations stored.

DESTDIR

DESTDIR on make install.

LIMITS

A Hash with the bounds of numeric types available to the C compiler used to build Ruby. To access this constant, first run require 'rbconfig/sizeof'.

require 'rbconfig/sizeof'
RUBY_PLATFORM # => "x64-mingw-ucrt"
RbConfig::LIMITS.fetch_values('FIXNUM_MAX', 'LONG_MAX')
# => [1073741823, 2147483647]

MAKEFILE_CONFIG

Almost same with CONFIG. MAKEFILE_CONFIG has other variable reference like below.

MAKEFILE_CONFIG["bindir"] = "$(exec_prefix)/bin"

The values of this constant is used for creating Makefile.

require 'rbconfig'

print <<-END_OF_MAKEFILE
prefix = #{RbConfig::MAKEFILE_CONFIG['prefix']}
exec_prefix = #{RbConfig::MAKEFILE_CONFIG['exec_prefix']}
bindir = #{RbConfig::MAKEFILE_CONFIG['bindir']}
END_OF_MAKEFILE

=> prefix = /usr/local
   exec_prefix = $(prefix)
   bindir = $(exec_prefix)/bin  MAKEFILE_CONFIG = {}

RbConfig.expand is used for resolving references like above in rbconfig.

require 'rbconfig'
p RbConfig.expand(RbConfig::MAKEFILE_CONFIG["bindir"])
# => "/usr/local/bin"

SIZEOF

A Hash with the byte size of C types available to the compiler used to build Ruby. To access this constant, first run require 'rbconfig/sizeof'.

require 'rbconfig/sizeof'
RUBY_PLATFORM                                  # => "x64-mingw-ucrt"
RbConfig::SIZEOF.fetch_values('long', 'void*') # => [4, 8]

TOPDIR

Ruby installed directory.

Public Class Methods

expand (val, config = CONFIG)

Source

# File rbconfig.rb, line 301
def RbConfig::expand(val, config = CONFIG)
  newval = val.gsub(/\$\$|\$\(([^()]+)\)|\$\{([^{}]+)\}/) {
    var = $&
    if !(v = $1 || $2)
      '$'
    elsif key = config[v = v[/\A[^:]+(?=(?::(.*?)=(.*))?\z)/]]
      pat, sub = $1, $2
      config[v] = false
      config[v] = RbConfig::expand(key, config)
      key = key.gsub(/#{Regexp.quote(pat)}(?=\s|\z)/n) {sub} if pat
      key
    else
      var
    end
  }
  val.replace(newval) unless newval == val
  val
end

RbConfig.expand(val)         -> string
RbConfig.expand(val, config) -> string

expands variable with given val value.

RbConfig.expand("$(bindir)") # => /home/foobar/all-ruby/ruby19x/bin

ruby ()

Source

# File rbconfig.rb, line 359
def RbConfig.ruby
  File.join(
    RbConfig::CONFIG["bindir"],
    RbConfig::CONFIG["ruby_install_name"] + RbConfig::CONFIG["EXEEXT"]
  )
end

RbConfig.ruby -> path

returns the absolute pathname of the ruby command.