How do I remove "permission denied" printout statements from the find program?

Question

Code

find / -name netcdf

Output

find: `/root/.dbus': Permission denied
find: `/root/.gconf': Permission denied
find: `/root/.gconfd': Permission denied
find: `/root/.gnome': Permission denied
find: `/root/.gnome2': Permission denied
find: `/root/.gnome2_private': Permission denied

Related: http://unix.stackexchange.com/q/290791/16920 – Léo Léopold Hertz 준영 Jul 04 '16 at 15:59 — Léo Léopold Hertz 준영, Jul 04 '16 at 15:59

score 68 · Accepted Answer · answered Aug 26 '11 at 00:40

Those messages are sent to stderr, and pretty much only those messages are generally seen on that output stream. You can close it or redirect it on the command-line.

$ find / -name netcdf 2>&-

or

$ find / -name netcdf 2>/dev/null

Also, if you are going to search the root directory (/), then it is often good to nice the process so find doesn't consume all the resources.

$ nice find / -name netcdf 2>&-

This decreases the priority of the process allowing other processes more time on the CPU. Of course if nothing else is using the CPU, it doesn't do anything. :) To be technical, the NI value (seen from ps -l) increase the PRI value. Lower PRI values have a higher priority. Compare ps -l with nice ps -l.

I do not like throwing out warnings. It is much better to handle them. Also, no escaping here in the field. — Léo Léopold Hertz 준영, Jul 04 '16 at 15:58
@LéoLéopoldHertz준영 WEll... if you can't see program output because yours screen is full of error crap.. which this is the case... — chrips, Jul 16 '19 at 05:14

score 32 · Answer 2 · edited Dec 26 '18 at 20:22

I would just like point out this answer by @Gilles in Exclude paths that make find complain about permissions - Unix & Linux Stack Exchange; it basically involves a construct for find that makes it not descend unreadable directories, and in that sense, is probably also a bit faster.

This would seem to work for me:

With GNU find or any other find that supports the -readable and -executable predicates:

find / -type d ! \( -readable -executable \) -prune -o -type f -name netcdf -print

or also this:

find / -type d ! -perm -g+r,u+r,o+r -prune -o -type f -name 'netcdf' -print

For some reason, I need to add all of the g+r,u+r,o+r (shortcut for that is a+r), otherwise if one of them is left out, I may still get "Permission Denied" hits.

Here is a breakdown of how I see this (note the -a (and) operator in find is implicit between two predicates):

find /         # find starting from path /
  -type d        # match type is directory
  ! -perm -a+r   # (and) match not permissions of `r`ead present 
  -prune         # ignore what matched above and do not descend into it
  -o             # or (whatever didn't match above)
  -type f        # match type is file
  -name 'netcdf' # (and) match name is 'netcdf'
  -print         # print what matched above

Note that without the last -print, I get some extra items shown (that have nothing to do with -name 'netcdf'); the -print ensures that only the name matches are printed (if any).

If find(1) can't descend into a directory, it won't. So checking beforehand if it can or not will just add work (check twice), and thus slow it down. — vonbrand, Mar 23 '14 at 15:41
@vonbrand it's necessary if you rely on find's exit status, because these permission errors make find exit with non-zero status — Ernest A, Mar 24 '15 at 08:47
I cannot get your proposal work. I get no output when expected output is full. http://unix.stackexchange.com/q/290791/16920 However, I think otherwise I think your method is the best way to go. — Léo Léopold Hertz 준영, Jul 04 '16 at 15:55
Wow, I can't believe it was so hard to find this answer, I now wish I could do more than just upvote it. — Wedge, Nov 08 '17 at 00:20
Note that the -readable way and the -perm way are not equivalent. — jarno, Mar 25 '21 at 17:46

score 13 · Answer 3 · answered Aug 26 '11 at 00:24

13

Use locate(1) instead:

$ locate netcdf

It will only show you files your user can see.

answered Aug 26 '11 at 00:24

Warren Young

72,032

3

This assumes that updatedb is running regularly. That is not the case on all Linux systems. – Arcege Aug 26 '11 at 00:48
5

If locate(1) is installed, its database should be updated periodically. If that isn't happening, I'd class that a misconfiguration rather than a fault of locate(1). Additionally, it only takes a few minutes to run it by hand in the rare cases where you're looking for a file that was added since the last DB update. I find myself doing that maybe half a dozen times per year, an overhead easily paid for from the speed advantage of locate(1) over find(1). – Warren Young Aug 26 '11 at 03:03

How do I remove "permission denied" printout statements from the find program?

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