replace_last

#!/usr/bin/python
"""
replace_last: Replace the last match in a file

Copyright (c) 2009, Richard Clark, Red Spider Limited <richard@redspider.co.nz>
Contributers include:
    Stephen J (Some script boilerplate code adopted from his NZPUG presentation)

See LICENSE file for details.

"""

import os, sys, random, logging, re
from optparse import OptionParser

WHENCE_RELATIVE = 1

logging.basicConfig(level=logging.WARN)
log = logging.getLogger('Skim')

def replace_last_generator(match, replace, file):
    buffer = ""
    rbuffer = None
    for line in file:
        if re.search(match, line):
            yield buffer
            if not rbuffer is None:
                yield rbuffer
            buffer = line
            rbuffer = None
        else:
            if rbuffer is None:
                rbuffer = line
            else:
                rbuffer += line
    
    yield re.sub(r'(.*)%s(.*?)$' % match, '\\1' + replace + '\\2', buffer)
    if not rbuffer is None:
        yield rbuffer

def replace_last(match, replace, file):
    """ Replace the last entry in the file """
    for chunk in replace_last_generator(match, replace, file):
        sys.stdout.write(chunk)

if __name__ == "__main__":
    usage = "usage: %prog [options] match replace [filename]"
    parser = OptionParser(usage="usage: %prog [options] match replace filename")
    parser.add_option("--verbose","-v",
                      help = "print debugging output",
                      action = "store_true")
    (options, args) = parser.parse_args()
    if options.verbose:
        log.setLevel(logging.DEBUG)
    
    log.debug("Verbose mode: %s" % options.verbose)
    
    (match, replace) = args[:2]    
    
    log.debug("Match: %s" % match)
    log.debug("Replace: %s" % replace)
    
    if len(args) > 2 and args[2] != '-':
        replace_last(match, replace, open(args[2],'rb'))
    else:
        replace_last(match, replace, sys.stdin)