Python subprocess readline with timeout

Question

Hello i have such problem, i need to execute some command and wait for it's output, but before reading output i need to write \n to pipe. This the unitest, so in some cases command witch i test don't answer and my testcase stopping at stdout.readline() and waiting for smth. So my question is, is it possible to set something like timeout to reading line.

cmd = ['some', 'list', 'of', 'commands']
fp = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
fp.stdin.write('\n')
fp.stdout.readline()
out, err = fp.communicate()

related: Stop reading process output in Python without hang? — jfs
– jfs, Commented Dec 24, 2014 at 16:42

Community · Accepted Answer · 2017-05-23 12:20:33Z

2

To wait for the response no more than a second:

from subprocess import Popen, PIPE

p = Popen(['command', 'the first argument', 'the second one', '3rd'],
          stdin=PIPE, stdout=PIPE, stderr=PIPE,
          universal_newlines=True)
out, err = p.communicate('\n', timeout=1) # write newline

The timeout feature is available on Python 2.x via the http://pypi.python.org/pypi/subprocess32/ backport of the 3.2+ subprocess module. See subprocess with timeout.

For solutions that use threads, signal.alarm, select, iocp, twisted, or just a temporary file, see the links to the related posts under your question.

edited May 23, 2017 at 12:20

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answered Dec 24, 2014 at 16:46

jfs

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user590028 · Accepted Answer · 2014-12-24 10:26:45Z

0

You pass input directly to communicate, https://docs.python.org/2/library/subprocess.html#subprocess.Popen.communicate, from docs

Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child.

Example:

cmd = ['some', 'list', 'of', 'commands']
fp = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = fp.communicate('\n')

answered Dec 24, 2014 at 10:26

user590028

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1 Comment

jfs Over a year ago

it doesn't address "is it possible to set something like timeout to reading line." part of the question.

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