#! /usr/bin/env python """Reverse grep. Usage: rgrep [-i] pattern file""" import sysimport reimport 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()