#! /usr/bin/env python

import sys

if len(sys.argv) < 4:
   sys.stderr.write("Usage: %s [-i] from_re to_re file....\n" % sys.argv[0])
   sys.exit(1)

import re
if sys.argv[1] == '-i':
    search = re.compile(sys.argv[2], re.IGNORECASE)
    replace = sys.argv[3]
    start = 4
else:
    search = re.compile(sys.argv[1])
    replace = sys.argv[2]
    start = 3

from fileinput import FileInput
files = FileInput(sys.argv[start:], inplace=1)

for line in files:
   line = search.sub(replace, line)
   sys.stdout.write(line)

files.close()