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How to test if a link exists
From: |
Mark Young |
Subject: |
How to test if a link exists |
Date: |
Fri, 21 Jun 2013 06:43:58 -0700 (PDT) |
User-agent: |
G2/1.0 |
Hi,
I stumbled into discovering that the -e test for a file does not report the
file as existing if the file is a dead symbolic link. This seems wrong to me.
Here's some test code:-
(WARNING it includes rm -f a b)
#!/bin/bash
bash --version
echo ""
rm -f a b
ln -s b a
[ -a a ] && echo "1. (test -a) File a exists, it's a dead link"
[ -e a ] && echo "1. (test -e) File a exists, it's a dead link"
[ -f a ] && echo "1. (test -f) File a exists, it's a dead link"
touch b
[ -a a ] && echo "2. (test -a) File a exists, it points to b"
[ -e a ] && echo "2. (test -e) File a exists, it points to b"
[ -f a ] && echo "2. (test -f) File a exists, it points to b"
When run on my CentOS v5.9 system I get the following
$ ./test
GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
2. (test -a) File a exists, it points to b
2. (test -e) File a exists, it points to b
2. (test -f) File a exists, it points to b
When run on Cygwin I also get basically the same
$ ./test
GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
2. (test -a) File a exists, it points to b
2. (test -e) File a exists, it points to b
2. (test -f) File a exists, it points to b
My feeling is that this is wrong and that I should be told that a exists even
though b doesn't. File 'a' does exist it is a dead symbolic link. So it
prevents me for instance creating a symbolic link:-
E.g.
$ ln -s c a
$ ls -l a b c
ls: b: No such file or directory
ls: c: No such file or directory
lrwxrwxrwx 1 marky tools 1 Jun 21 14:41 a -> b
Is this an error in bash?
What test should I use to decide if a file exists (including dead symbolic
links)?
Cheers,
Mark
- How to test if a link exists,
Mark Young <=