/Tools/scripts/rgrep.py

 1#! /usr/bin/env python
 2
 3"""Reverse grep.
 4
 5Usage: rgrep [-i] pattern file
 6"""
 7
 8import sys
 9import re
10import getopt
11
12def 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
57def usage(msg, code=2):
58    sys.stdout = sys.stderr
59    print msg
60    print __doc__
61    sys.exit(code)
62
63if __name__ == '__main__':
64    main()