Suppressing the output of a command run using 'system' method while running it in a ruby script.

Question

I am not sure if this makes sense but I am thinking if there is a way to suppress the output shown for a command when run using the system method in ruby? I mean it should just output true or false to STDOUT and not the output of the command. What I think is it can just only be done if the command can run silently and not from the system method. Can someone provide a bit more insight?

Thanks.

Answer 1

You can also use backticks or %x

Answer 2

After a call to system the exit code is in the special variable $? so if useradd returns different values to indicate if the user was successfully added (e.g. 0 for success) then you can do the following:

system('useradd xx > /dev/null')
if $? == 0
  puts 'added'
else
  puts 'failed'
end

where the redirect to /dev/null will suppress the output.

Alternatively if the program being called does not use its exit code to indicate success or failure you can use backticks and search for a particular substring in the output e.g.

if `useradd xx`.include? 'success'
  puts 'it worked'
else
  puts 'failed to add user'
end