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()