#!/usr/bin/python

import sys

string_from = sys.argv[1]
string_to = sys.argv[2]
files = sys.argv[3:]

for filename in files:
    f = open(filename, "r+")
    data = f.read()
    data = data.replace(string_from, string_to)
    f.seek(0)
    f.truncate()
    f.write(data)
    f.close()