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