Set timeout for a shell command in python
I wanted to run a shell command in python without knowing if the shell command is going to exit within reasonable time (adplay that was, sometimes it simply hangs).
Update: the “task” module of Rob Hooft seems to solve this exact problem. At the time I wrote this, the python.net website was down. I leave my solution here just for archive purpose.
def timeout_command(command, timeout): """call shell-command and either return its output or kill it if it doesn't normally exit within timeout seconds and return None""" import subprocess, datetime, os, time, signal start = datetime.datetime.now() process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE) while process.poll() is None: time.sleep(0.1) now = datetime.datetime.now() if (now - start).seconds> timeout: os.kill(process.pid, signal.SIGKILL) os.waitpid(-1, os.WNOHANG) return None return process.stdout.read()
>>> output = timeout_command(["sleep", "10"], 2) None >>> output = timeout_command(["sleep", "1"], 2)
The process can be killed when it has run for too long (the
os.waitpid waits for the kill to end and avoids defunct-processes) and furthermore the Popen’ed process’ printed is caught and returned if it doesn’t timeout. However,
subprocess.Popen is called with a list as argument. That means, that the command isn’t passed to a shell and furthermore you can just call one command with options, nothing more.