Print the supplied template once for each line of stdin

textsub.py

#!/usr/bin/env python

import sys

if len(sys.argv) == 1:
    text = "{text}"
    message = '''\
Error: no argument supplied.

This program prints the template once for each line of stdin. {text} in the template is replaced with the line from stdin.

Usage:
  {argv0} <template> < data

Examples:
  cat names.txt | {argv0} 'Hello {text}. Goodbye {text}!'
  {argv0} 'ping -c 1 {text}' < hosts.txt'''
    print(message.format(text=text, argv0=sys.argv[0]))

    sys.exit(1)


for line in sys.stdin.readlines():
    print(sys.argv[1].format(text=line.strip()))