#!/usr/bin/env python

import sys
from argparse import ArgumentParser

# Set up options
parser=ArgumentParser(description="Sponge file before writing output: grep foo file.txt | sponge file.txt",
                      epilog="This tool is a modification from http://joeyh.name/code/moreutils/ with the same name.")
parser.add_argument("-a",action="store_true",dest="append",default=False,
                  help="Append to file instead of overwriting")
parser.add_argument(type=str,dest="file",
                  help="File to write to")
options=parser.parse_args()

# Read data
data=sys.stdin.read()

# choose mode
mode="w"
if options.append:
    mode="a"
# Write the file
writer=open(options.file, mode)
writer.write(data)
writer.close()