#!/usr/bin/env python
"""
Simple script to remove lines from a file.
"""
import os, sys, re

def main():
    if len(sys.argv) != 3:
        print "Usage: %s <filename> <>\n" \
              "\tRemoves from <filename> the lines matching <reg.exp.>" \
              % os.path.basename(sys.argv[0])
        sys.exit(1)
    
    filename, pattern = sys.argv[1:]
    if not os.path.isfile(filename):
        print "Error: cannot find file '%s'" % filename
        sys.exit(1)
    
    try:
        regexp = re.compile(pattern)
    except re.error, v:
        print "Error: invalid regular expression %r (%s)" % (pattern, v)
        sys.exit(1)
    
    # read the file in memory skipping the matched lines
    lines = [ l
              for l in open(filename) ]
    orig_size = len(lines)
    lines = [ l
              for l in lines
              if not regexp.search(l) ]
    final_size = len(lines)
    # rename the original to make a backup copy
    if os.path.exists(filename + "~"):
        os.remove(filename + "~")
    os.rename(filename, filename + "~")
    # write out the file
    open(filename, "w").writelines(lines)
    print "Removed %d lines out of %d in file %s, matching pattern %r" \
          % (orig_size - final_size, orig_size, filename, pattern)

if __name__ == '__main__':
    main()