Table of Contents

Invoke a blocking process howto

>>["ls", "-l"])  # doesn't capture output
CompletedProcess(args=['ls', '-l'], returncode=0)

>>["ls", "-l", "/dev/null"], stdout=subprocess.PIPE)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n')

Invoke a non-blocking process howto

proc = Popen(['ls', '-l'], stdout=PIPE)
# Read the subprocess's stdout, stdderr, and blocks until it exits
outs, errs = proc.communicate(timeout=15)

Using PIPE discussion

as specified in open

Warning This will deadlock when using stdout=PIPE and/or stderr=PIPE and the child process generates enough output to a pipe such that it blocks waiting for the OS pipe buffer to accept more data. Use communicate() to avoid that.

Use communicate() rather than .stdin.write, or to avoid deadlocks due to any of the other OS pipe buffersfilling up and blocking the child process.

When to use shell=True discussion