Question

I have a problem.

I want to run a ruby script from another ruby script and capture it’s output information while letting it output to the screen too.

runner

#!/usr/bin/env ruby
print "Enter your password: "
password = gets.chomp
puts "Here is your password: #{password}"

The script file that I run:

start.rb

output = `runner`
puts output.match(/Here is your (password: .*)/).captures[0].to_s

As you see here there is a problem.

In the first line of start.rb the screen is empty.

I cannot see the “Enter your password: ” in runner.

Is there a way to display the output of the runner script before it’s finished, and still let me capture it to a string so I can process the information, eg. using match like in this example?

Answer 1

runner.rb

STDOUT.print "Enter your password: "
password = gets.chomp
puts "Here is your password: #{password}"

Note STDOUT.print

start.rb

require "stringio"

buffer = StringIO.new
$stdout = buffer

require "runner"

$stdout = STDOUT
buffer.rewind

puts buffer.read.match(/Here is your (password: .*)/).captures[0].to_s

output

Enter your password: hello
password: hello

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Read more…

I recently did a write-up on this here: Output Buffering with Ruby