1#! /usr/bin/env python
2
3# 3)  System Test
4#
5#     Given a list of directories, report any bogus symbolic links contained
6#     anywhere in those subtrees.  A bogus symbolic link is one that cannot
7#     be resolved because it points to a nonexistent or otherwise
8#     unresolvable file.  Do *not* use an external find executable.
9#     Directories may be very very deep.  Print a warning immediately if the
10#     system you're running on doesn't support symbolic links.
11
12# This implementation:
13# - takes one optional argument, using the current directory as default
14# - uses chdir to increase performance
15# - sorts the names per directory
16# - prints output lines of the form "path1 -> path2" as it goes
17# - prints error messages about directories it can't list or chdir into
18
19import os
20import sys
21from stat import *
22
23def main():
24    try:
25        # Note: can't test for presence of lstat -- it's always there
26        dummy = os.readlink
27    except AttributeError:
28        print "This system doesn't have symbolic links"
29        sys.exit(0)
30    if sys.argv[1:]:
31        prefix = sys.argv[1]
32    else:
33        prefix = ''
34    if prefix:
35        os.chdir(prefix)
36        if prefix[-1:] != '/': prefix = prefix + '/'
37        reportboguslinks(prefix)
38    else:
39        reportboguslinks('')
40
41def reportboguslinks(prefix):
42    try:
43        names = os.listdir('.')
44    except os.error, msg:
45        print "%s%s: can't list: %s" % (prefix, '.', msg)
46        return
47    names.sort()
48    for name in names:
49        if name == os.curdir or name == os.pardir:
50            continue
51        try:
52            mode = os.lstat(name)[ST_MODE]
53        except os.error:
54            print "%s%s: can't stat: %s" % (prefix, name, msg)
55            continue
56        if S_ISLNK(mode):
57            try:
58                os.stat(name)
59            except os.error:
60                print "%s%s -> %s" % \
61                      (prefix, name, os.readlink(name))
62        elif S_ISDIR(mode):
63            try:
64                os.chdir(name)
65            except os.error, msg:
66                print "%s%s: can't chdir: %s" % \
67                      (prefix, name, msg)
68                continue
69            try:
70                reportboguslinks(prefix + name + '/')
71            finally:
72                os.chdir('..')
73
74main()
75