Files
Yukihiro "Matz" Matsumoto eb8c177824 mruby-bin-mrb: add compiler-free runtime executor gem
The `mrb` command executes only precompiled RiteBinary (.mrb) files
without depending on mruby-compiler. This enables smaller binaries
for embedded deployments where scripts are precompiled on a
development machine.

Co-authored-by: Claude <noreply@anthropic.com>
2026-04-23 19:25:22 +09:00

2.5 KiB

mruby-bin-mrb

mrb is a lightweight mruby runtime that executes only precompiled RiteBinary (.mrb) files. Unlike the full mruby command, it does not depend on mruby-compiler, resulting in a significantly smaller binary.

This gem is intended for embedded deployments where Ruby scripts are precompiled on a development machine and only the runtime is needed on the target device.

Size comparison

By excluding mruby-compiler (and gems that depend on it such as mruby-eval, mruby-binding, and mruby-bin-mirb), the text segment can be reduced by approximately 300KB or more, depending on the build configuration.

Usage

mrb [switches] programfile.mrb [arguments]

Options

  • -d - set debugging flags (set $DEBUG to true)
  • -r library - load a library (.mrb) before executing your script
  • -v - print version number, then run in verbose mode
  • --verbose - run in verbose mode
  • --version - print the version
  • --copyright - print the copyright

Workflow

# On the development machine (with full mruby + mrbc):
mrbc -o program.mrb program.rb

# On the target device (with mrb only):
mrb program.mrb

# Load a precompiled library before the main program:
mrb -r lib.mrb program.mrb

# Pass arguments to the script:
mrb program.mrb arg1 arg2

Build configuration example

To build a minimal mruby with only the mrb runtime:

# build_config/runtime.rb
MRuby::Build.new do |conf|
  conf.toolchain

  # Use a gembox that does not pull in the compiler.
  # For example, the default gembox does not require it.
  conf.gembox 'default'

  # The runtime-only executor (no compiler dependency)
  conf.gem :core => 'mruby-bin-mrb'

  # Do NOT include these (they require mruby-compiler):
  #   conf.gem :core => 'mruby-bin-mruby'
  #   conf.gem :core => 'mruby-bin-mirb'
  #   conf.gem :core => 'mruby-eval'
  #   conf.gem :core => 'mruby-binding'
end

Differences from mruby command

Feature mruby mrb
Execute .rb files yes no
Execute .mrb files yes yes
-e inline code yes no
-c syntax check yes no
-b force binary mode yes not needed (always binary)
Requires mruby-compiler yes no

License

MIT License - see the mruby LICENSE file.