Using the answers here and linked in Mihai's answer, I put together a function that meets these requirements:
As a bonus, this one will also return STDOUT in cases where the shell command exits successfully (0) and puts anything on STDOUT. In this manner, it differs from system
, which simply returns true
in such cases.
Code follows. The specific function is system_quietly
:
require 'open3'
class ShellError < StandardError; end
#actual function:
def system_quietly(*cmd)
exit_status=nil
err=nil
out=nil
Open3.popen3(*cmd) do |stdin, stdout, stderr, wait_thread|
err = stderr.gets(nil)
out = stdout.gets(nil)
[stdin, stdout, stderr].each{|stream| stream.send('close')}
exit_status = wait_thread.value
end
if exit_status.to_i > 0
err = err.chomp if err
raise ShellError, err
elsif out
return out.chomp
else
return true
end
end
#calling it:
begin
puts system_quietly('which', 'ruby')
rescue ShellError
abort "Looks like you don't have the `ruby` command. Odd."
end
#output: => "/Users/me/.rvm/rubies/ruby-1.9.2-p136/bin/ruby"