The /proc filesystem is a wealth of useful information. Found this one today looking for something unrelated.
You can read the limits file of a running process to find its currently defined limits, this is helpful for things like Max open files. You can use this to verify that the settings in /etc/security/limits.conf matches the running process.
~]$ cat /proc/5610/limits Limit Soft Limit Hard Limit Units Max cpu time unlimited unlimited seconds Max file size unlimited unlimited bytes Max data size unlimited unlimited bytes Max stack size 8388608 unlimited bytes Max core file size 0 unlimited bytes Max resident set unlimited unlimited bytes Max processes 3874 3874 processes Max open files 1024 1024 files Max locked memory 65536 65536 bytes Max address space unlimited unlimited bytes Max file locks unlimited unlimited locks Max pending signals 3874 3874 signals Max msgqueue size 819200 819200 bytes Max nice priority 0 0 Max realtime priority 0 0 Max realtime timeout unlimited unlimited us