How can you determine the current limit on the number of files open simultaneously in a Linux system?

In Linux, the current limit on the number of simultaneously open files can be checked using the ulimit command or by viewing the relevant files in /proc.

Main methods:

1. Using the ulimit command (bash):

ulimit -n

It displays the maximum number of open files for the current process.

2. To view limits for the current user:

ulimit -a | grep open

3. To view system-wide limits in /proc:

cat /proc/sys/fs/file-max

This is the maximum number of open files for the entire system.

4. To check for a specific process, look in /proc/<pid>/limits:

cat /proc/$$/limits | grep "Max open files"

Thus, ulimit -n is the simplest way to find out the open files limit for the current session.