#! /usr/bin/env python | |
"""Reverse grep. | |
Usage: rgrep [-i] pattern file | |
""" | |
import sys | |
import re | |
import getopt | |
def main(): | |
bufsize = 64*1024 | |
reflags = 0 | |
opts, args = getopt.getopt(sys.argv[1:], "i") | |
for o, a in opts: | |
if o == '-i': | |
reflags = reflags | re.IGNORECASE | |
if len(args) < 2: | |
usage("not enough arguments") | |
if len(args) > 2: | |
usage("exactly one file argument required") | |
pattern, filename = args | |
try: | |
prog = re.compile(pattern, reflags) | |
except re.error, msg: | |
usage("error in regular expression: %s" % str(msg)) | |
try: | |
f = open(filename) | |
except IOError, msg: | |
usage("can't open %s: %s" % (repr(filename), str(msg)), 1) | |
f.seek(0, 2) | |
pos = f.tell() | |
leftover = None | |
while pos > 0: | |
size = min(pos, bufsize) | |
pos = pos - size | |
f.seek(pos) | |
buffer = f.read(size) | |
lines = buffer.split("\n") | |
del buffer | |
if leftover is None: | |
if not lines[-1]: | |
del lines[-1] | |
else: | |
lines[-1] = lines[-1] + leftover | |
if pos > 0: | |
leftover = lines[0] | |
del lines[0] | |
else: | |
leftover = None | |
lines.reverse() | |
for line in lines: | |
if prog.search(line): | |
print line | |
def usage(msg, code=2): | |
sys.stdout = sys.stderr | |
print msg | |
print __doc__ | |
sys.exit(code) | |
if __name__ == '__main__': | |
main() |