Catching command-line errors using %x

Question

Whenever you want to execute something on the command line, you can use the following syntax:

%x(command to run)

However, I want to catch a

Answer 1

Here's how to use Ruby's open3:

require 'open3'
include Open3

stdin, stdout, stderr = popen3('date')
stdin.close

puts
puts "Reading STDOUT"
print stdout.read
stdout.close

puts
puts "Reading STDERR"
print stderr.read
stderr.close
# >> 
# >> Reading STDOUT
# >> Sat Jan 22 20:03:13 MST 2011
# >> 
# >> Reading STDERR

popen3 returns IO streams for STDIN, STDOUT and STDERR, allowing you to do I/O to the opened app.

Many command-line apps require their STDIN to be closed before they'll process their input.

You have to read from the returned STDOUT and STDERR pipes. They don't automatically shove content into a mystical variable.

In general, I like using a block with popen3 because it handles cleaning up behind itself.

Look through the examples in the Open3 doc. There's lots of nice functionality.