How do I (recursively) detect all symlinks in a directory that identify their target in an absolute as opposed to in a relative way?
Since these links are very likely to break when an entire directory tree is moved I would like to have a way of identifying them.
Even relative links may break if the directory tree is moved (if they happen to point outside the root of the directory tree), but I think this is addressed in this question.
To find absolute links, you can use find's -lname option if your find supports that (it's available at least in GNU find, on FreeBSD and macOS):
find . -type l -lname '/*'
This asks find to print the names of files which are symbolic links and whose content (target) matches /* using shell globbing.
Strictly speaking, POSIX specifies that absolute pathnames start with one / or three or more /; to match that, you can use
find . -lname '/*' ! -lname '//*' -o -lname '///*'
On what systems is //foo/bar different from /foo/bar? has more details on that.
(Thanks to Sato Katsura for pointing out that -lname is GNU-specific, to fd0 for mentioning that it's actually also available on at least FreeBSD and macOS, and to Stéphane Chazelas for bringing up the POSIX absolute pathname definition.)
find ./ -t l -exec ls -l {} \; which should be a safe alternative. It would be easy to parse its output do do whatever is needed.
– Centimane
Sep 09 '16 at 16:11
You may find the symlinks utility useful:
$ symlinks -r .
other_fs: /home/chazelas/test/bin -> /bin
dangling: /home/chazelas/test/DIR/foo -> foo
dangling: /home/chazelas/test/blah -> not-here
absolute: /home/chazelas/test/chazelas -> /home/chazelas
And can fix the links for you. Here with -t to tell what it would do:
$ symlinks -rct .
other_fs: /home/chazelas/test/bin -> /bin
dangling: /home/chazelas/test/DIR/foo -> foo
dangling: /home/chazelas/test/blah -> not-here
absolute: /home/chazelas/test/chazelas -> /home/chazelas
changed: /home/chazelas/test/chazelas -> ../../chazelas
