redirecting stdin, stdout, stderr from python

saw a nice comment in a post on python daemon forks that explains how to redirect std* pipes, even when they are accessed from c. i've been frustrated trying to figure that out before.

More reliable i/o stream redirection. Just reassigning to the sys streams is not 100% effective if you are importing modules that write to stdin and stdout from C code. Perhaps the modules shouldn't do that, but this code will make sure that all stdin and stdout will go where you expect it to.

import os, sys

out_log = file('/out/log/file/name', 'a+')
err_log = file('/err/log/file/name', 'a+', 0)
dev_null = file('/dev/null', 'r')
sys.stdout.flush()

sys.stderr.flush()

os.dup2(out_log.fileno(), sys.stdout.fileno())

os.dup2(err_log.fileno(), sys.stderr.fileno())
os.dup2(dev_null.fileno(), sys.stdin.fileno())

(and another poster suggests closing sys.std* before duping.) cool. i need to remember this next time i wrap somebody's code that thinks it's a good idea to barf on the terminal without a --quiet option.

also, the demon implementation looks pretty clean, with extra tidbits sprinkled into the comments, and the author explains the reasons for doing things. i don't think i will need the double fork for my udev script, but the first fork will be necessary.