How to find "dead" symbolic links ?

[xuo]

Hi,

I know how to know if a file or dir is a symbolic link. But how can I know that the target does NOT exist ?

Ex :
ln1 -> tutu
ln2 -> titi
titi does not exist, tutu does. tutu and toto can be either dir or file. How can I make the difference between the 2 symbolic links ? I would like to use a tcsh script with simple commands such as ls, find ...

I think it is possible with find but I did not succeed to make it work.
I had another idea which was :
if the target is a dir and that I try to "cd" inside but can't, then the link is dead. But how to do if the target is a file ? Moreover, doing "cd" in each possible symbolic link and going back to current dir can be very long. This is a possible workaround but not a good idea.

Regards.

Eric.

[Smither]

file /symbolic/link/

If it's broken it'll say something along the lines of:
/usr/bin/ear: broken symbolic link to `/usr/lib/erlang/bin/ear'

This searches my system for them:

for i in `find /`; do if (test -h $i); then file $i|grep broken; fi; done

Make sure you check it yourself instead of piping it to something else - a symbolic link with broken in the name will show too.

[xuo]

Hi,

I did not know this command. I think it will help me a lot.

Thank you.

Eric.

[ghostdog74]

find / -type l ! -exec test -r {} \; -print

[drl]

Hi.

Observations: these two methods differ in two ways. As noted, the first may produce false positives if the pathname contains the string "broken". The first is also much slower. I benchmarked the two on a system of about 12K directories and 120K files:

real    5m24.875s
user    0m22.586s
sys     4m45.621s

real    0m19.110s
user    0m0.893s
sys     0m2.875s

Except for the anomalies mentioned above, both produced the same results. The method posted by ghostdog74 is far faster ... cheers, drl

[xuo]

Hi,

Thank you to all of you. I'll try both of them. This will help me to understand these options of the find command that I didn't know.

Regards.

Eric.

[pooryorick]

The following command finds only broken symbolic links:

find -L -type l

This works because "-L" causes find to dereference symbolic links, in which case only broken links will have type "l". This is probably unique to gnu find (from findutils)

more info:
ynform.org slash w slash Pub slash UnixCommandEquivalents