file io - Python `tee` stdout of child process -

is there way in python equivalent of unix command line tee? i'm doing typical fork/exec pattern, , i'd stdout child appear in both log file , on stdout of parent simultaneously without requiring buffering.

in python code instance, stdout of child ends in log file, not in stdout of parent.

pid = os.fork() logfile = open(path,"w") if pid == 0:   os.dup2(logfile.fileno(),1)     os.execv(cmd) 

edit: not wish use subprocess module. i'm doing complicated stuff child process requires me call fork manually.

here have working solution without using subprocess module. although, use tee process while still using exec* functions suite custom subprocess (just use stdin=subprocess.pipe , duplicate descriptor stdout).

import os, time, sys  pr, pw = os.pipe() pid = os.fork()  if pid == 0:     os.close(pw)     os.dup2(pr, sys.stdin.fileno())     os.close(pr)     os.execv('/usr/bin/tee', ['tee', 'log.txt']) else:     os.close(pr)     os.dup2(pw, sys.stdout.fileno())     os.close(pw)      pid2 = os.fork()      if pid2 == 0:         # replace custom process call         os.execv('/usr/bin/yes', ['yes'])     else:         try:             while true:                 time.sleep(1)         except keyboardinterrupt:             pass 

note tee command, internally, same thing ben suggested in answer: reading input , looping on output file descriptors while writing them. may more efficient because of optimized implementation , because it's written in c, have overhead of different pipes (don't know sure solution more efficient, in opinion, reassigning custom file-like object stdout more elegant solution).

some more resources:

• how duplicate sys.stdout log file in python?
• http://www.shallowsky.com/blog/programming/python-tee.html