RTFM or just code: recursively compare directories and files in two paths

Recursively comparing directories and files in two provided paths is probably a common problem and for sure there's a solution out there.

bad. I didn't find (search for) one before coding my own solution. I just did search intensively for such a solution before writing this post (to avoid that comment saying something like: hey man it was solved twenty years back!). The simplest solution, using diff:

$ diff -r -q /tmp/a /tmp/b
Only in /tmp/a/b: c
Only in /tmp/a/b/d: a.txt
Only in /tmp/b/b: y.txt
Files /tmp/a/x.txt and /tmp/b/x.txt differ
-r for recursive; -q for quiet: do not actually show the diff but just tell files differ.

Anyway I had already coded a script and want to share it. It's just a clone of `diff -r -q` written in python and able to be extended for your own purposes.

# -*- coding: UTF-8 -*-

Recursively compare directories and files in two provided paths.
- Report what files are distinct in path1 and path2.
- Report what files and directories are not present in both paths.

import filecmp
import os
import os.path
import sys

def diff(basepath, path1, path2):
    # STEP 1: iterate on all path1 paths (directories and filenames) and compare with path2
    # - report if path2 does not exist
    # - when path is a file, report if path1 differ from path2
    common_paths = []
    for path in os.listdir(path1):
        abs1 = os.path.join(path1, path)
        abs2 = os.path.join(path2, path)
        relative = abs1[len(basepath)+1:]
        if not os.path.exists(abs2):
            print "Only in %s: %s" % (os.path.dirname(abs1), path)

        if os.path.isfile(abs1):
            r = filecmp.cmp(abs1, abs2)
            if not r:
                print "Files %s and %s differ" % (abs1, abs2)
        elif os.path.isdir(abs1):
            paths = diff(basepath, abs1, abs2)

    # STEP 2: the other way: iterate on all path2 paths and
    # - report if path in path2 does not exist in path1
    for path in os.listdir(path2):
        abs1 = os.path.join(path1, path)
        abs2 = os.path.join(path2, path)
        relative = abs2[len(basepath)+1:]
        if not os.path.exists(abs1):
            print "Only in %s: %s" % (os.path.dirname(abs2), path)

    return common_paths

if __name__ == "__main__":
    if len(sys.argv) != 3:
        print "Usage: diff.py {path1} {path2}"
    paths = sys.argv[1:]
    for path in paths:
        if not os.path.exists(path):
            print "%s does not exist!" % path

    basepath = os.path.commonprefix(paths).rstrip('/')
    diff(basepath, *paths)