View system open file limits (nofile) and how many file in use by user

system_limits.sh

# View system limit configurations
cat /etc/security/limits.conf

# There may be overrides to limits in limits.d
cat /etc/security/limits.d/90-nproc.conf

# find active number of file descriptors per user
ps -A x | grep [w]ww-prod | awk '{print $1}' | xargs -I '{}' ls /proc/{}/fd  | wc -l

# Alternate count of file decriptors
lsof -u www-prod | grep ' REG\|FIFO\|unix ' | grep -v ' mem    REG ' | grep -v ' txt    REG ' | grep -v ' DEL    REG ' | wc -l

# Listing file descriptors for an individual process
lsof -p 49122 | grep ' REG\|FIFO\|unix ' | grep -v ' mem    REG ' | grep -v ' txt    REG ' | grep -v ' DEL    REG '
ls -lA /proc/49122/fd


# the nproc limit includes the number of threads for the user, not just processes

# Get summary of count of processes and threads by user
ps h -Led -o user | sort | uniq -c | sort -n

# count total number of processes/threads used per user
ps h -Lfu www-prod | wc -l

# Get summary of processes for a user with a column indicating the number of threads each process has running
ps -o nlwp,pid,lwp,args -u www-prod | sort -n