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 shared-testcase

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rgrep.py

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#! /usr/bin/env python3

"""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 as msg:

usage("error in regular expression: %s" % msg)

try:

f = open(filename)

except IOError as msg:

usage("can't open %r: %s" % (filename, msg), 1)

with f:

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

for line in reversed(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()