Redirect all current process output to a file

redirectTest.py

#!/usr/bin/python
# coding: utf-8
from sys import stderr, stdout
from os import dup, dup2, close
from subprocess import Popen, PIPE
from contextlib import contextmanager
from time import sleep
from traceback import print_exc

@contextmanager
def copyOutput(file):
	print "Output is logged to", file
	stdout.flush()
	stderr.flush()
	tee=Popen(['tee', file], stdin=PIPE, preexec_fn=setpgrp)
	out = dup(stdout.fileno())
	err = dup(stderr.fileno())
	dup2(tee.stdin.fileno(), stdout.fileno())
	dup2(tee.stdin.fileno(), stderr.fileno())
	try:
		yield
	except:
		stdout.flush()
		stderr.flush()
		print_exc()
	finally:
		stdout.flush()
		stderr.flush()
		dup2(out, stdout.fileno())
		dup2(err, stderr.fileno())
		close(out)
		close(err)
		tee.stdin.close()
		tee.wait()
		print file, "closed"



print "Writing to standard output"


with redirectOutput('/tmp/out.log'):
	print "Writing to both standard output and file"

print "Writing to standard output"
sleep(10)

The main point is redirection of used C libraries output which is not processed by Python routines (raw system writes).