A context manager to temporarily redirect stdout or stderr e.g.: ```python with stdchannel_redirected(sys.stderr, os.devnull): ... ```

stdchannel_redirected.py

import contextlib


@contextlib.contextmanager
def stdchannel_redirected(stdchannel, dest_filename):
    """
    A context manager to temporarily redirect stdout or stderr

    e.g.:

    with stdchannel_redirected(sys.stderr, os.devnull):
        if compiler.has_function('clock_gettime', libraries=['rt']):
            libraries.append('rt')
    """

    try:
        oldstdchannel = os.dup(stdchannel.fileno())
        dest_file = open(dest_filename, 'w')
        os.dup2(dest_file.fileno(), stdchannel.fileno())

        yield
    finally:
        if oldstdchannel is not None:
            os.dup2(oldstdchannel, stdchannel.fileno())
        if dest_file is not None:
            dest_file.close()

Sample usage:

with stdchannel_redirected(sys.stderr, os.devnull):
    if compiler.has_function('clock_gettime', libraries=['rt']):
        libraries.append('rt')

Used in the setup.py of pymssql: https://code.google.com/p/pymssql/source/detail?r=dff75e59fde5c814e160b973ba94496f1b033499#

Blogged about this at http://marc-abramowitz.com/archives/2013/07/19/python-context-manager-for-redirected-stdout-and-stderr/ and tweeted about this at https://twitter.com/MSAbramo/status/358262914920087552