rgrep.py

#! /usr/bin/env python

"""Reverse grep.

Usage: rgrep [-i] pattern file
"""

importsys
importre
importgetopt

defmain():
bufsize=64*1024
reflags=0
opts, args=getopt.getopt(sys.argv[1:], "i")
foro, ainopts:
ifo=='-i':
reflags=reflags|re.IGNORECASE
iflen(args) <2:
usage("not enough arguments")
iflen(args) >2:
usage("exactly one file argument required")
pattern, filename=args
try:
prog=re.compile(pattern, reflags)
exceptre.error, msg:
usage("error in regular expression: %s"%str(msg))
try:
f=open(filename)
exceptIOError, msg:
usage("can't open %s: %s"% (repr(filename), str(msg)), 1)
f.seek(0, 2)
pos=f.tell()
leftover=None
whilepos>0:
size=min(pos, bufsize)
pos=pos-size
f.seek(pos)
buffer=f.read(size)
lines=buffer.split("\n")
delbuffer
ifleftoverisNone:
ifnotlines[-1]:
dellines[-1]
else:
lines[-1] =lines[-1] +leftover
ifpos>0:
leftover=lines[0]
dellines[0]
else:
leftover=None
lines.reverse()
forlineinlines:
ifprog.search(line):
printline

defusage(msg, code=2):
sys.stdout=sys.stderr
printmsg
print__doc__
sys.exit(code)

if__name__=='__main__':
main()