Number of open files

cat /proc/sys/fs/nr_open
cat /proc/sys/fs/file-max
cat /proc/sys/fs/file-nr
ulimit -n

Per process:

# prlimit 
RESOURCE   DESCRIPTION                             SOFT      HARD UNITS
AS         address space limit                unlimited unlimited bytes
CORE       max core file size                 unlimited unlimited bytes
CPU        CPU time                           unlimited unlimited seconds
DATA       max data size                      unlimited unlimited bytes
FSIZE      max file size                      unlimited unlimited bytes
LOCKS      max number of file locks held      unlimited unlimited locks
MEMLOCK    max locked-in-memory address space   8388608   8388608 bytes
MSGQUEUE   max bytes in POSIX mqueues            819200    819200 bytes
NICE       max nice prio allowed to raise             0         0 
NOFILE     max number of open files                1024    524288 files
NPROC      max number of processes                62249     62249 processes
RSS        max resident set size              unlimited unlimited bytes
RTPRIO     max real-time priority                     0         0 
RTTIME     timeout for real-time tasks        unlimited unlimited microsecs
SIGPENDING max number of pending signals          62249     62249 signals
STACK      max stack size                       8388608 unlimited bytes

cat /proc/PID/limits