Factoring out the listen(2) half of an ucspi unixserver.

unixlisten

#!/usr/bin/env python
'''
Like unixserver(1), but just listen and exec the subordinate program
with the listening socket as stdin. The subordinate program still needs
to call accept(2) on stdin.
'''

import sys
import os
import socket
import errno

prog = sys.argv.pop(0)
path = sys.argv.pop(0)

# Remove socket from previous run, if it exists.
try:
  os.unlink(path)
except OSError, e:
  if e.errno != errno.ENOENT:
    raise

s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
s.bind(path)
s.listen(32)
os.dup2(s.fileno(),0)
os.close(s.fileno())
os.execvp(sys.argv[0],sys.argv)