What does the -tulpn option mean for netstat?

For finding out which ports of the machine are being opening by which services, I used:

netstat -tulpn

I checked the man page for netstat command, but I found nothing about this option. What's the meaning of the -tulpn option?

As answered in https://serverfault.com/questions/387935/whats-the-difference-betwen-the-single-dash-and-double-dash-flags-on-shell-comm, in a Linux command line;

A single hyphen can be followed by multiple single-character flags.

A double hyphen prefixes a single multi-character option.

If you look at netstat man page, you will see that (Note that, netstat -tulpn is equivalent to netstat -t -u -l -p -n):

--tcp|-t

--udp|-u

-l, --listening
   Show only listening sockets.  (These are omitted by default.)

-p, --program
   Show the PID and name of the program to which each socket belongs.

--numeric, -n
   Show numerical addresses instead of trying to determine symbolic host, port or user names.

So, your command is equivalent to the following long form also:

netstat --tcp --udp --listening --program --numeric

In addition to man netstat you can type info netstat to get a shorter summary and longer explanation:

NETSTAT(8)                      Linux Programmer's Manual                      NETSTAT(8)

NAME
       netstat  -  Print  network connections, routing tables, interface statistics, mas‐
       querade connections, and multicast memberships

SYNOPSIS
       netstat [address_family_options] [--tcp|-t] [--udp|-u] [--raw|-w] [--listening|-l]
       [--all|-a]  [--numeric|-n]  [--numeric-hosts]  [--numeric-ports] [--numeric-users]
       [--symbolic|-N] [--extend|-e[--extend|-e]]  [--timers|-o]  [--program|-p]  [--ver‐
       bose|-v] [--continuous|-c]

For -t -u -l -p -n above you see --tcp, --udp, --listen, --program and --numeric without having to scroll.

Scrolling down you can see verbose explanations.

What does the -tulpn option mean for netstat?

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