ulimit:tldr:6f479

The command ulimit -a is used in Unix-like operating systems to display the current resource limits for the active user. It provides information about various limits set on system resources, such as the maximum number of open files, the maximum amount of virtual memory, the maximum stack size, etc.

When you run ulimit -a, it will print a list of different resource limits and their respective values. Here's an example of its output:

core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 31451
max locked memory       (kbytes, -l) 65536
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 99
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 31451
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

In this example, it shows the maximum number of open files is set to 1024, the maximum stack size is 8192 kilobytes, and so on. The value "unlimited" means that there is no fixed limit imposed on that particular resource.