checking a bash command in a if statement in Ruby

Question

How can I check the return value (true/false) of bash command in an if statement in Ruby. I want something like this to work,

if ("/usr/bin/fs wscell > /dev/null 2>&1")
                has_afs = "true"
        else
                has_afs = "false"
        end

It complains with the following error meaning, it will always return true.

 (irb):5: warning: string literal in condition

What's the correct syntax ?

UPDATE :

 /usr/bin/fs wscell 

looks for afs installed and running condition. It will throw a string like this,

 This workstation belongs to cell <afs_server_name>

If afs is not running, the command exits with status 1

Answer 1

You want backticks rather than double-quotes. To check a program's output:

has_afs = `/usr/bin/fs wscell > /dev/null 2>&1` == SOMETHING ? 'true' : 'false'

Where SOMETHING is filled in with what you're looking for.

Answer 2

You should probably use system() or Backticks and then check the exit status of the command ($?.exitstatus):

Heres a good quicktip read: http://rubyquicktips.com/post/5862861056/execute-shell-commands)

UPDATE:

system("/usr/bin/fs wscell > /dev/null 2>&1")  # Returns false if command failed
has_afs = $?.exitstatus != 1  # Check if afs is running