The Linux set command allows you to change the value of shell options or to display the names and values of shell variables. Rarely used, it is a bash builtin, but is quite a bit more complicated than most builtins.
If you use the command without any arguments, you will get a list of all the settings—the names and values of all shell variables and functions. Watch out though! You’ll end up with a torrent of output flowing down your screen. There are just short of 3,000 lines of output on my Fedora system:
$ set | wc -l
The top of the list looks like what you see below, but the output gets considerably more complicated as you move through it.
Source:: Network World – Data Center