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Aw: How to test if a link exists


From: John Kearney
Subject: Aw: How to test if a link exists
Date: Fri, 21 Jun 2013 23:49:49 +0200 (CEST)

   check out
   help test
   if you want to test fot both you can do

   [ -e file -o -h file ] || echo file not present.

   AFAIK the current behaviour is intentional and is the most useful.

   cheers


   Gesendet: Freitag, 21. Juni 2013 um 15:43 Uhr
   Von: "Mark Young" <address@hidden>
   An: address@hidden
   Betreff: How to test if a link exists
   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
   <[1]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

References

   1. http://gnu.org/licenses/gpl.html


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