Find is returning "find: .: Permission denied", but I am not searching in

Question

I have an enormous shell script that I am troubleshooting. I often run the script from my home directory with a sudo. Whenever a find is executed, I see this error:

find: .: Permission denied

It is true that root does not have access to my home directory (which is the current working directory or . in the error above), but I'm not asking find to do anything in my home directory and would rather it leave it alone entirely.

To really drive the point home I ran this:

sudo find /dev -maxdepth 1 -type f

and still get the same error. If the -type -f is removed the error is appended to the end of the expected results. Of course, if I cd /dev there is no error..probably since root has access to /dev. Even though I don't think it's causing problems, it makes the script look buggy. How can I prevent the script from showing these errors?

Answer 1

I ran:

strace find /dev -maxdepth 1

on GNU/Linux (Ubuntu) and it turns out that find uses fchdir syscall to traverse the directory tree and finally executes fchdir to go back to the original working directory. Here's a snippet:

open(".", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_NOFOLLOW) = 4
fchdir(4)                               = 0

... irrelevant ...

write(1, "/dev\n", 5)                   = 5
open("/dev", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 5
fcntl64(5, F_GETFD)                     = 0x1 (flags FD_CLOEXEC)
fchdir(5)                               = 0

... potentially more fchdirs ...

fchdir(4)                               = 0
close(4)                                = 0

My hint? cd /tmp (or some other fully accessible directory) before running find.