How to find all log files recursively while leaving out one specific access denied path?

Question

I'm using Linux Mint 18.3 and I have a school task to find all log files in one linux machine without any error messages. I need to put together a command and explain it throughly. I think I have found a way to use find but there is one access denied message regarding gvfs that I'm not sure how to handle. Can you help me assemble a simple and smart command that doesn't just blindly filter out any error messages but only leaves out those places where it's really no sense to look? My first try:

# find / -type f -name '*.log'

seems to return all log files but the result includes:

find: '/run/user/1000/gvfs': Permission denied

Then I tried to leave out one folder:

# find / -type d \( -name run \) -prune -o -type f -name '*.log' -print

but it doesn't seem smart to leave out the whole run folder so started to specify, to narrow it to one specific path maybe. Found this post, and unix.stackexchange.com/a/77592 answer, and tried to leave out this specific path:

# find / -name '*.log' -path '/run/user/1000/gvfs' -prune -o -type f -name '*.log' -print

but it doesn't seem to work as I expect, returning still the same, among seemingly all log files:

find: '/run/user/1000/gvfs': Permission denied

Now I run into understanding problem where I'm thinking wrong or is leaving out this one specific path the simplest and smartest thing to do at all.

Answer 1

Log files are stored in /var/log so there's really no need to run find on the entire root directory. If you insist on doing so and want to exclude that directory so that you don't get errors then your syntax should be:

find / -wholename /run -prune -o -type f -name '*.log' -print

That directory is the mountpoint for FUSE and doesn't contain any log files and /run itself has directories (atleast in Centos, Fedora, and RHEL) inside which will give permission errors so the above command will exclude the directory altogether. I don't have Mint installed so you can edit the commmand to prune lower until you receive errors.

Also, one thing to keep in mind is that log files don't always end in .log such as messages, dmesg, cron, and secure.

Answer 2

Just do:

 find / -type f -name '*.log' 2>/dev/null

or

find /var -type f -name '*.log'

as far as logs should be in var

Answer 3

The correct idiom for avoiding the "permission denied" error messages is:

find <root-path> ! -readable -prune -o <rest of your find arguments>

Applying that to your original homework answer would yield:

find / ! -readable -prune -o -type f -name "*.log"

That should satisfy your requirement to "assemble a simple and smart command". It also fulfills the requirement "that doesn't just blindly filter out any error messages" because it only filters out unreadable stuff. Your final requirement "but only leaves out those places where it's really no sense to look" is another matter entirely, and would make a nice separate question, to wit, 'Is there a way for a script to find the default system log root directory, on the particular system on which the script is running?'. I'm unaware of an environment variable for that.