#! /usr/bin/env python

# 3)  System Test

#

#     Given a list of directories, report any bogus symbolic links contained

#     anywhere in those subtrees.  A bogus symbolic link is one that cannot

#     be resolved because it points to a nonexistent or otherwise

#     unresolvable file.  Do *not* use an external find executable.

#     Directories may be very very deep.  Print a warning immediately if the

#     system you're running on doesn't support symbolic links.

# This implementation:

# - takes one optional argument, using the current directory as default

# - uses chdir to increase performance

# - sorts the names per directory

# - prints output lines of the form "path1 -> path2" as it goes

# - prints error messages about directories it can't list or chdir into

import os

import sys

from stat import *

def main():

    try:

        # Note: can't test for presence of lstat -- it's always there

        dummy = os.readlink

    except AttributeError:

        print "This system doesn't have symbolic links"

        sys.exit(0)

    if sys.argv[1:]:

        prefix = sys.argv[1]

    else:

        prefix = ''

    if prefix:

        os.chdir(prefix)

        if prefix[-1:] != '/': prefix = prefix + '/'

        reportboguslinks(prefix)

    else:

        reportboguslinks('')

def reportboguslinks(prefix):

    try:

        names = os.listdir('.')

    except os.error, msg:

        print "%s%s: can't list: %s" % (prefix, '.', msg)

        return

    names.sort()

    for name in names:

        if name == os.curdir or name == os.pardir:

            continue

        try:

            mode = os.lstat(name)[ST_MODE]

        except os.error:

            print "%s%s: can't stat: %s" % (prefix, name, msg)

            continue

        if S_ISLNK(mode):

            try:

                os.stat(name)

            except os.error:

                print "%s%s -> %s" % \

                      (prefix, name, os.readlink(name))

        elif S_ISDIR(mode):

            try:

                os.chdir(name)

            except os.error, msg:

                print "%s%s: can't chdir: %s" % \

                      (prefix, name, msg)

                continue

            try:

                reportboguslinks(prefix + name + '/')

            finally:

                os.chdir('..')

main()