My question is simple: Can I expect()
to see certain output on stderr using pexpect? It seems pexpect.spawn()
can only be used to expect output on stdout.
Utopian example:
import pexpect child = pexpect.spawn(...) child.expect("hi", fd=pexpect.STDERR)
Or in prose, "expect the string 'hi' on stderr".
I have not found any mention of such a facility in the docs, but I do note that the child
instance has a stderr
attribute...
A hack which semi-achieves what I want is to redirect stderr to stdout in the spawn arguments, then we can use regular expect()
. There must be a better way?
Cheers
For posterity, and based on the comment by Thomas K , this seems to do what you want:
import os
import subprocess
from pexpect import fdpexpect
program = ['/path/to/command', '--arg1', 'value1', '--arg2', 'value2']
devNull = open(os.devnull, 'w')
command = subprocess.Popen(program, stdout=devNull,
stdin=subprocess.PIPE, stderr=subprocess.PIPE)
child = fdpexpect.fdspawn(command.stderr)
child.expect('hi')
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