Say I have a function like below, how do I capture the output of the Process.spawn call? I should also be able to kill the process if it takes longer than a specified timeout.
Note that the function must also be cross-platform (Windows/Linux).
def execute_with_timeout!(command)
begin
pid = Process.spawn(command) # How do I capture output of this process?
status = Timeout::timeout(5) {
Process.wait(pid)
}
rescue Timeout::Error
Process.kill('KILL', pid)
end
end
Thanks.
You can use IO.pipe and tell Process.spawn to use the redirected output without the need of external gem.
Of course, only starting with Ruby 1.9.2 (and I personally recommend 1.9.3)
The following is a simple implementation used by Spinach BDD internally to capture both out and err outputs:
# stdout, stderr pipes
rout, wout = IO.pipe
rerr, werr = IO.pipe
pid = Process.spawn(command, :out => wout, :err => werr)
_, status = Process.wait2(pid)
# close write ends so we could read them
wout.close
werr.close
@stdout = rout.readlines.join("\n")
@stderr = rerr.readlines.join("\n")
# dispose the read ends of the pipes
rout.close
rerr.close
@last_exit_status = status.exitstatus
The original source is in features/support/filesystem.rb
Is highly recommended you read Ruby's own Process.spawn documentation.
Hope this helps.
PS: I left the timeout implementation as homework for you ;-)
I followed Anselm's advice in his post on the Ruby forum here.
The function looks like this -
def execute_with_timeout!(command)
begin
pipe = IO.popen(command, 'r')
rescue Exception => e
raise "Execution of command #{command} unsuccessful"
end
output = ""
begin
status = Timeout::timeout(timeout) {
Process.waitpid2(pipe.pid)
output = pipe.gets(nil)
}
rescue Timeout::Error
Process.kill('KILL', pipe.pid)
end
pipe.close
output
end
This does the job, but I'd rather use a third-party gem that wraps this functionality. Anyone have any better ways of doing this? I have tried Terminator, it does exactly what I want but it does not seem to work on Windows.
