CODEWITHSUNDEEP
rubyprocessforkstdoutstdin
pmerino
pmerino

Reputation: 6130

How to control a subprocess stdin, stdout, etc within Ruby?

I'm building a small script where I'd like to launch the user's shell but redirect it's stdin and stdout so I can control them on the code. Would this be possible? I already tried with this code (which might be wrong though):

new_stdout, new_stdin = IO.pipe
pid = fork {
    $stdout.reopen new_stdin
    exec(ENV['SHELL'])
}

new_stdin.puts "Test"
Process.wait(pid)

This does nothing more than launch a new shell instance.

Thanks!

Upvotes: 2

Views: 2619

Answers (2)

Gurpartap Singh
Gurpartap Singh

Reputation: 2764

While you may just use IO.pipe or Open3.popen3 method if simplicity is what your program requires. For advanced usage, I do it in cognizant project in the part, that you may refer to, where it demonizes a process and collects its standard input/output/error streams using Ruby 1.9's ::Process::spawn manually at https://github.com/Gurpartap/cognizant/blob/master/lib/cognizant/process/execution.rb

Upvotes: 0

DigitalRoss
DigitalRoss

Reputation: 146261

Something like this, perhaps?

IO.popen 'sh', 'r+' do |io|
  io.puts 'echo how now brown cow | tr a-z A-Z'
  result = io.gets
  p [:result, result.size, result]
end

Upvotes: 3

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