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 an error or at least get the response so I can parse it correctly. I tried setting:

result = %x(command to run)

and using a try-catch

begin
  %x(command to run)
rescue
  "didn't work"
end

to no avail. How can I capture the results instead of having them printed out?

Answer 1

So this doesn't directly answer your question (won't capture the command's output). But instead of trying begin/rescue, you can just check the exit code ($?) of the command:

%x(command to run)
unless $? == 0
   "ack! error occurred"
end

Edit: Just remembered this new project. I think it does exactly what you want:

https://github.com/envato/safe_shell

Answer 2

You might want to redirect stderr to stdout:

result = %x(command to run 2>&1)

Or if you want to separate the error messages from the actual output, you can use popen3:

require 'open3'
stdin, stdout, stderr = Open3.popen3("find /proc")

Then you can read the actual output from stdout and error messages from stderr.