Crystal Stdio

A small Crystal library for capturing standard I/O streams.

Installation

Add this to your application's shard.yml:

dependencies:
  stdio:
    github: mosop/stdio

Usage

require "stdio"

out, err, in = Stdio.capture do |io|
  STDOUT.puts ":)"
  STDERR.puts ":("
  io.in.puts ":P"
  [io.out.gets, io.err.gets, STDIN.gets]
end

puts out # prints ":)"
puts err # prints ":("
puts in  # prints ":P"

Decapturing

The out and err methods returns decaptured I/Os. The type of the I/O means that the I/O is not capturing the standard stream any more. In other words, you can not capture the standard streams any more in the same yielded block after calling out or err.

Stdio.capture do |io|
  STDOUT.puts ":)" # captured
  io.out.gets # decaptured and taken ":)\n"
  STDOUT.puts ":X" # prints ":X", not captured
end

Why should I/Os be decaptured? Because a process easily hangs up when you send any waiting methods to the I/Os that are not decaptured.

To access I/Os keeping capturing and control waiting by yourself, use the out! and err! methods.

Stdio.capture do |io|
  STDOUT.puts ":)"
  io.out!.gets # => ":)\n"
  STDOUT.puts ":X"
  io.out!.gets # => ":X\n"
  io.out!.gets # waits
end

Release Notes

• v0.1.3
  • Capture#out!, Capture#err!
• v0.1.2
  • STDIN

Contributing

1. Fork it ( https://github.com/mosop/stdio/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• mosop - creator, maintainer