How to verify the target of a symbolic link points toward a particular path

Question

Within a bash script, I know I can check if a file is a symbolic link with the following syntax

if [ -L $path ]

Does any one know how I would test if that path was linked to a particular path? E.g. I want to check whether the target of $path is /some/where.

possible duplicate of [How do I check if a file is a symbolic link to a directory?](http://unix.stackexchange.com/questions/96907/how-do-i-check-if-a-file-is-a-symbolic-link-to-a-directory) — A.B., Mar 24 '15 at 20:54
Do you mean linked to _by_ a particular path? Couldn't you do a `readlink` on the known path and compare it against the path you're testing? — Bratchley, Mar 24 '15 at 20:55
@Bratchley. Yes, that's what I meant.. thanks for the answer. — BillMan, Mar 24 '15 at 20:57
I strongly urge you to always put shell variables in quotes (e.g., `if [ -L "$path" ]` ) unless you have a good reason not to and you're sure you know what you're doing. — G-Man Says 'Reinstate Monica', Mar 25 '15 at 00:02
@G-Man thanks for the great feedback.. subconsciously I know to do that, but forget it in practice.. the reinforcement helps. — BillMan, Mar 25 '15 at 13:23

score 31 · Accepted Answer · answered Mar 25 '15 at 01:34

31

If you want to check whether $path is a symbolic link whose target is /some/where, you can use the readlink utility. It isn't POSIX, but it's available on many systems (GNU/Linux, BusyBox, *BSD, …).

if [ "$(readlink -- "$path")" = /some/where ]; then …

Note that this is an exact text comparison. If the target of the link is /some//where, or if it's where and the value of $path is /some/link, then the texts won't match.

Many versions of readlink support the option -f, which canonicalizes the path by expanding all symbolic links.

Many shells, including dash, ksh, bash and zsh, support the -ef operator in the test builtin to test whether two files are the same (hard links to the same file, after following symbolic links). This feature is also widely supported but not POSIX.

if [ "$path" -ef "/some/where" ]; then …

answered Mar 25 '15 at 01:34

Gilles 'SO- stop being evil'

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the first example does not work when the link points to a relative path... – inemanja Nov 04 '19 at 12:20
1

@inemanja Sure it does. But as I state, this is a _text_ comparison. It treats different paths to the same target as different. If you want to test whether the target of a symbolic link is a particular **file**, rather than a particular **path**, use one of the methods I describe below. – Gilles 'SO- stop being evil' Nov 04 '19 at 12:46
It's not safe to treat file location as strings for that exact reason - the first example compares strings hence it shows that "/dir/file.txt" and "/dir/../dir/../dir/file.txt" are different files, and they are not. The second example is much more precise. – inemanja Jul 09 '20 at 15:42
How about wrapping the path in `$(realpath "../dir/../otherdir/file.ext")` ? – Mogens TrasherDK Dec 10 '21 at 12:21
@MogensTrasherDK How about that? I don't understand what you're asking. – Gilles 'SO- stop being evil' Dec 10 '21 at 19:53
If `relative` path is a problem, translate to `absolute` path. Is that more clear? – Mogens TrasherDK Dec 12 '21 at 03:48
BTW. I agree that the `if [ "$path" -ef "/some/where" ]; then` is probably a better option inmost cases. – Mogens TrasherDK Dec 12 '21 at 03:56

How to verify the target of a symbolic link points toward a particular path

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