Tools/scripts/rgrep.py

   1 #! /usr/bin/env python
   2
   3 """Reverse grep.
   4
   5 Usage: rgrep [-i] pattern file
   6 """
   7
   8 import sys
   9 import re
  10 import string
  11 import getopt
  12
  13 def main():
  14     bufsize = 64*1024
  15     reflags = 0
  16     opts, args = getopt.getopt(sys.argv[1:], "i")
  17     for o, a in opts:
  18         if o == '-i':
  19             reflags = reflags | re.IGNORECASE
  20     if len(args) < 2:
  21         usage("not enough arguments")
  22     if len(args) > 2:
  23         usage("exactly one file argument required")
  24     pattern, filename = args
  25     try:
  26         prog = re.compile(pattern, reflags)
  27     except re.error, msg:
  28         usage("error in regular expression: %s" % str(msg))
  29     try:
  30         f = open(filename)
  31     except IOError, msg:
  32         usage("can't open %s: %s" % (repr(filename), str(msg)), 1)
  33     f.seek(0, 2)
  34     pos = f.tell()
  35     leftover = None
  36     while pos > 0:
  37         size = min(pos, bufsize)
  38         pos = pos - size
  39         f.seek(pos)
  40         buffer = f.read(size)
  41         lines = string.split(buffer, "\n")
  42         del buffer
  43         if leftover is None:
  44             if not lines[-1]:
  45                 del lines[-1]
  46         else:
  47             lines[-1] = lines[-1] + leftover
  48         if pos > 0:
  49             leftover = lines[0]
  50             del lines[0]
  51         else:
  52             leftover = None
  53         lines.reverse()
  54         for line in lines:
  55             if prog.search(line):
  56                 print line
  57
  58 def usage(msg, code=2):
  59     sys.stdout = sys.stderr
  60     print msg
  61     print __doc__
  62     sys.exit(code)
  63
  64 if __name__ == '__main__':
  65     main()