Recursively rename UPPERCASE filename extensions to lowercase

fixext.py

#!/usr/bin/env python
"""Epic script to rename scary uppercase extensions (like .JPG) to
more friendly lowercase (like .jpg).

How to use
==========

Recursively rename all files in the current directory::

    fixext

Recursively rename all files in another directory::

    fixext /media/vulpix

Disable recursion with ``-d``::

    fixext -d /media/ralts

Dry run (test it without actually renaming anything)::

    fixext -n /media/vulpix

You can combine options, e.g.::

    fixext -nd /media/ralts

That's it! Less is more, I say.
"""

from optparse import OptionParser
import os
import sys

def recursive_walk(path):
    for root, dirs, files in os.walk(path):
        for name in files:
            yield os.path.join(root, name)

def simple_walk(path):
    for name in os.listdir(path):
        if os.path.isfile(name):
            yield os.path.join(path, name)

def fix(name):
    base, ext = os.path.splitext(name)
    return base + ext.lower()

def main():
    parser = OptionParser(usage='usage: %prog [options] [DIR...]')
    parser.add_option('-d', '--no-recursion', action='store_false',
                      dest='recursion', default=True,
                      help="Don't recurse into subdirectories")
    parser.add_option('-n', '--dry-run', action='store_true',
                      dest='dry_run', default=False,
                      help="Dry run: test it without actually renaming anything")

    options, args = parser.parse_args()

    if len(args) == 0:
        paths = [os.getcwdu()]
    else:
        paths = args

    if options.recursion:
        walker = recursive_walk
    else:
        walker = simple_walk

    dry_run = options.dry_run

    n_renamed = 0
    n_errors = 0

    for path in paths:
        for name in walker(path):
            new_name = fix(name)
            if name != new_name:
                if os.path.exists(new_name):
                    print >>sys.stderr, "** Warning: destination '%s' already exists" % new_name
                    n_errors += 1
                else:
                    print new_name
                    if not dry_run:
                        os.rename(name, new_name)
                    n_renamed += 1

    print >>sys.stderr, "%d files renamed successfully, with %d errors" % (n_renamed, n_errors)

    if n_errors > 0:
        sys.exit(1)

if __name__ == '__main__':
    main()