How to check ulimit usage

Question

Is there any way to check the usage of the ulimits for a given user? I know that you can change ulimits for a single process when you start it up or for a single shell when running but I want to be able to "monitor" how close a user is to hitting their limits. I am planning on writing a bash script that will report back to statsd the current usage percentage. Specifically, I want to track:

1. open files (ulimit -n)
2. max user processes (ulimit -u)
3. pending signals (ulimit -i)

What I want out is the percentage of usage (0-100).

Answer 1

Maybe this helps for the first question:

If you know the process IDs (PID) of the specific user you can get the limits for each process with:

cat /proc/<PID>/limits

You can get the number of opened files for each PID with:

ls -1 /proc/<PID>/fd | wc -l

And then just compare the value of Max open files with the number of open file descriptors from the second command to get a percentage.

Answer 2

Output the current user's percentage of open files, proc, and pending signals, by several inconvenient methods and standard tools:

paste <(grep 'open files\|processes\|pending signals' \
              /proc/self/limits | cut -c27-38)        \
      <(i=`whoami`
        lsof -n -u $i 2> /dev/null | 
             tail -n +2 | 
             awk {'print $9'} | 
             wc -l
        ps --no-headers -U $i -u $i u | wc -l
        ps -u $i -o pid= | 
             xargs printf "/proc/%s/status\n" |
             xargs grep -s 'SigPnd' |
             sed 's/.*\t//' | 
             paste -sd+ | 
             bc ; ) \
      <(grep 'open files\|processes\|pending signals' \
             /proc/self/limits | 
                   cut -c1-19) | 
while read a b name ; do 
    printf '%3i%%  %s\n' $((${b}00/a)) "$name"
done

Output on my system:

 16%  Max processes
 12%  Max open files
  0%  Max pending signals

---

Assuming those numbers are good, what this answer shows is that it can be done in shell, but probably shouldn't, unless there are much better shell methods. Rather, this Q would be better done with gcc, or python, etc.

Answer 3

Ulimits are properties of processes and are inherited to child processes.

You cannot get the limits for another process.