Show percentage used of 1) per-process ulimit open files, and 2) system-wide open files limit.

show_limits.sh

#!/bin/bash

printf "%-20s %10s   %10s   %14s\n" "Process" "Ulimit" "Used" "% Ulimit Used"
length=62
printf -v line '%*s' "$length"
echo ${line// /-}
# gather proceses to list from all of /var/run/
for f in $(find /var/run/ -type f -name "*.pid" | sort)
# gather processes to list from monit
#for f in $(grep pidfile /etc/monit.d/* | awk '{print $6}' | sort)
do
    name=$(echo $f | awk -F'/' '{print $NF}' | awk -F"." '{print $1}')
    n=$(cat $f)
    if [[ $n && ${n-x} ]]
    then
        if [ -d "/proc/$n" ]
        then
            current=$(ls /proc/$n/fd/ |wc -l)
            limit=$(cat /proc/$n/limits | grep "Max open files" | awk '{print $5}')
            percent=$(echo "scale=4; ( $current / $limit ) * 100.0" | bc)
            printf "%-20s %10d   %10d   %13.2f%%\n" $name $limit $current $percent
        else
            printf "%-35s %20s\n" $name "ERROR: No Process Found"
        fi
    else
        printf "%-35s %20s\n" $name "ERROR: No PID in file"
    fi
done

echo

fs_nr=$(sysctl fs.file-nr)
fs_used=$(echo $fs_nr | awk '{print $3}')
fs_limit=$(echo $fs_nr | awk '{print $5}')
fs_percent_used=$(echo "scale=4; ($fs_used / $fs_limit) * 100.0" | bc)
printf "%-10s %10s %16s\n" "FS Limit" "FS Used" "% Limit Used"
length=62
printf -v line '%*s' "$length"
echo ${line// /-}
printf "%-10d %10d %15.2f%%\n" $fs_limit $fs_used $fs_percent_used
echo