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 return decapturing I/Os. The type of the I/O means that the I/O is not capturing the standard I/O any more. In other words, you can not capture the decaptured standard I/O again 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" # ":X" is printed, not captured
end

Why is decapturing needed? Because a process easily hangs up when you send any waiting methods to I/Os that are still capturing the standard I/Os.

To read 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