The best answers to the question “How to use `subprocess` command with pipes” in the category Dev.
I want to use
ps -A | grep 'process_name'.
I tried various solutions but so far nothing worked. Can someone guide me how to do it?
Or you can always use the communicate method on the subprocess objects.
cmd = "ps -A|grep 'process_name'" ps = subprocess.Popen(cmd,shell=True,stdout=subprocess.PIPE,stderr=subprocess.STDOUT) output = ps.communicate() print(output)
The communicate method returns a tuple of the standard output and the standard error.
To use a pipe with the
subprocess module, you have to pass
However, this isn’t really advisable for various reasons, not least of which is security. Instead, create the
grep processes separately, and pipe the output from one into the other, like so:
ps = subprocess.Popen(('ps', '-A'), stdout=subprocess.PIPE) output = subprocess.check_output(('grep', 'process_name'), stdin=ps.stdout) ps.wait()
In your particular case, however, the simple solution is to call
subprocess.check_output(('ps', '-A')) and then
str.find on the output.
import subprocess ps = subprocess.run(['ps', '-A'], check=True, capture_output=True) processNames = subprocess.run(['grep', 'process_name'], input=ps.stdout, capture_output=True) print(processNames.stdout)
See the documentation on setting up a pipeline using subprocess: http://docs.python.org/2/library/subprocess.html#replacing-shell-pipeline
I haven’t tested the following code example but it should be roughly what you want:
query = "process_name" ps_process = Popen(["ps", "-A"], stdout=PIPE) grep_process = Popen(["grep", query], stdin=ps_process.stdout, stdout=PIPE) ps_process.stdout.close() # Allow ps_process to receive a SIGPIPE if grep_process exits. output = grep_process.communicate()