Running Commands

I

What a command is

Open Konsole: press the Super key (the Windows key), type konsole, press Enter.

A command is a program’s name typed into the terminal. Pressing Enter runs it, and whatever it prints underneath is its answer.

Spelling and capitalization matter exactly, as in programming. The machine cannot guess what you meant.

Try one. Type this and press Enter:

whoami

It prints your username. That is the whole loop: you asked the laptop a question, it answered.

Try a second one:

echo hello

echo simply repeats back its arguments in the same order they were given, on the same line. So echo hello prints hello back, and echo a b c would print a b c. It never changes the order and never uses extra lines.

II

Arguments: what to work on

Most commands take arguments: extra words after the program name that say what to work on. echo hello already had one — hello is the argument, the thing to repeat.

Arguments can pile up. Try:

echo hello there Jesse

You should see hello there Jesse. Each extra word is another argument, and echo repeats them all. Here is that command taken apart — the first word is the command, the second is the 1st argument, the third is the 2nd argument, and so on:

Arguments are not always words to repeat. Some tell the program what to work on instead — a folder, a file, a name. The next section meets a command built around exactly that.

III

Meet ls

ls lists the contents of a directory. That is all it does, and it is the command you will use most.

By itself, it lists where the terminal is standing. Since Konsole starts in your home folder, try:

ls

You should see your home folder’s contents: Documents, Downloads, Pictures, and the rest.

With an argument, it lists that folder instead of the one you are standing in:

ls /

/ (just a slash, called the root) is the very top of the whole system. Every folder on the laptop lives under it, including your home. It always has files in it, so it always prints something.

/ is the argument telling ls which folder. Look through the listing for home — that is the folder your home directory lives inside.

IV

Flags: how to change it

A flag is an argument that changes how a program behaves instead of what it works on. Flags start with dashes: one dash for short flags (-l), two for whole words (--help).

The dash is how the program tells flags apart from normal arguments.

Run both of these and compare:

ls
ls -l

Same program, same folder, different behavior — the -l flag did that.

Flags can combine with arguments:

ls -l /

Read the labels as a sentence: list the contents, including extra details by using the long listing, for this directory. Program, flag, argument, in that order.

V

Asking for help with --help

Nearly every command answers the --help flag with a short summary of how to use it. It is the friendliest help there is, written for quick reminders. Try:

ls --help

You will see a list of flags with one-line explanations. Do not read it all. The habit is: skim for the flag that sounds like what you want, try it, and come back when you want another.

Prove the habit works. Somewhere in that output is -a, which also shows hidden files (names starting with a dot). Find its one-line explanation first, then try:

ls -a

If the listing suddenly grows longer with dotfiles, you just learned a flag from --help and used it. That is the whole skill.

Most commands have --help. When a guide tells you to use a flag you have not seen, running <command> --help first is never wrong.

VI

The manual with man

Every command also has a manual page, the complete reference.

Be warned: a man page will look overwhelming at first. Long, dense, full of flags you will never use. That is normal and not a test. It becomes useful the more commands you already know, because then you are looking up one detail instead of learning everything.

For now, three moves are the whole skill. Open the page with:

man ls

Use the Up and Down arrow keys to scroll through the page. When you have seen enough, press q to quit back to the prompt.

You do not need to understand the page — knowing it exists and how to leave it is the lesson.

Review what this taught. A command is a program name plus Enter. Arguments say what to work on. Flags, starting with dashes, say how. --help is the short friendly summary; man is the complete reference for later. Every later guide assumes exactly this and nothing more.