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Shell Command for Symbolic Link Targets


 
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# 1  
Old 02-20-2008
Shell Command for Symbolic Link Targets

**DUP post in Shell Programming and Scripting ***
Hello,

I'm still learning the ins and outs of how to combine multiple Unix commands together (specifically AIX), but I'm looking to do the following (only on local files):

1. Find all symbolic links that are not set up using absolute pathnames
2. Find all symbolic links that are broken (ie, target does not exist).

My original idea was to find all symbolic links, pipe it to a file and then read the file, but we'd like to do it as a single command without creating new files.

I've only been able to come up with the following (which I believe shows all the local symbolic links):
find / -type l \( -fstype jfs -o -fstype jfs2 \)

Thanks for any and all help.

Ben

edit: I think I may have found the answer to #2, is it correct?
find / -type l | (while read FN ; do test -e "$FN" || ls -l "$FN"; done)

Last edited by bdizenhouse; 02-21-2008 at 10:12 AM..
# 2  
Old 02-21-2008
I have now been asked to also provide a count of the results.

So I think I found the following solutions:
#2
find / -type l | (while read FN ; do test -e "$FN" || ls -l "$FN"; done)
and
find / -type l | (while read FN ; do test -e "$FN" || ls -l "$FN"; done) | grep -c '[a-z]'

#1
find / -type l | (while read FN ; do test -e "$FN" | file -h "$FN" | grep 'symbolic link to [^/]' ; done)
and
find / -type l | (while read FN ; do test -e "$FN" | file -h "$FN" | grep 'symbolic link to [^/]' ; done) | grep -c 'symbolic link to [^/]'

Are these correct? I want to make sure I'm only looking at local filesystems only. Also how can I suppress the messages like "ls: 0653-341 The file xxx does not exist." or "find: 0652-019 The status on xxx is not valid."


Thanks for any and all help.

Ben
# 3  
Old 02-21-2008
I will include some more general aspects in my reply:

Quote:
Originally Posted by bdizenhouse
I have now been asked to also provide a count of the results.
You have line-oriented output, yes? "wc -l" counts lines ...

Quote:
I want to make sure I'm only looking at local filesystems only.
You chose a way of iteratively selecting all the local ones: fstype=jfs, fstype=jfs2, ... . This is possible but such problems can be solved from both sides, though: either by including everything you need or by excluding everything you do not need. "All local filesystems" is the same as "all non-remote filesystems", yes?:

find ....... ! -fstype nfs

Means "all filesystems except nfs", which should be what you want. This would include not only jfs and jfs2 but also some more obscure FS types, which also exist.

Quote:
Also how can I suppress the messages like "ls: 0653-341 The file xxx does not exist." or "find: 0652-019 The status on xxx is not valid.
This comes because you issue "find" under your user id and your user is probably not allowed to access everything. This would probably be different if you issue the command as root user. Anyways, the error messages go to a separate I/O channel in UNIX (to <stderr>), which only per default points to the same output device as <stdout>. You can safely redirect the error messages (and only them) with putting your valuable output in jeopardy:

find ..... 2> /dev/null

redirects the outcome of the <stderr> file descriptor to /dev/null, the big bit bucket instead of /dev/yourpseudoterminal, where it clutters your screen.

I hope this helps and, btw.: we have a great and very active AIX special interest group here in the forum, which i by now would like to shamelessly advertise. I am looking forward to see you there.

bakunin
# 4  
Old 02-21-2008
Shell Commands for Symbolic Links

Thank you very much for the indepth solution.

I'm still very new to the Unix world, and where I am, we mainly deal with AIX, so I will definately check out the forums here.

So I've come to the conclusion to use the following 2 commands:

(find all non-absolute symbolic links)
find / -type l ! -fstype nfs 2> /dev/null | (while read FN ; do test -e "$FN" | file -h "$FN" | grep 'symbolic link to [^/]' ; done) | wc -l

(final all broken symbolic links)
find / -type l ! -fstype nfs 2> /dev/null | (while read FN ; do test -e "$FN" || ls -l "$FN" 2> /dev/null; done) | wc -l

Thanks very much for the help!
ben
 

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