Unix commands come in all shapes and sizes, from simple and common to rare and hellish. The command itself is a rather brief set of letters (usually, but not always), possibly followed by options and / or arguments. To open an UNIX Terminal window, click on the "Terminal" icon from Applications/Accessories menus.

When you first login, your current working directory is your home directory. Your home directory has the same name as your user-name, for example, reny, and it is where your personal files and subdirectories are saved. To find out what is in your home directory, type:

$ ls

The ls command ( lowercase L and lowercase S ) lists the contents of your current working directory.

Try these simple commands, the bold indicate what you should type.

$ date
Thu Feb 16 09:35:12 GMT 2011
$ _

Note that after the date, time, and time zone are displayed, the shell prompt reappears ready for your next command. Next enter who to see who is on the system.

The response is a list of all active users, the terminals they are logged on, and the date and time they last logged on.

$ who
iwonka tty1a Feb16 10:05
stan     tty2a Feb16 15:23
$ _

Unix lets you enter two or more commands on the same line. Simply enter a semi-colon between each command; then press Enter after the final command.

$ date; who

The next example shows what happens if you enter a nonexistent command.

$ amelia
amelia: not found

If you enter a command that is unknown to Unix, you get the not found message, followed by the shell prompt.
It's important at this early to realize that it's almost impossible to damage a computer system by mistyping a command. There are, to be sure, a few dangerous commands, such as rm and rmdir, that if used rashly, can erase files you may not want to erase.

Here are few commands that you can try:

Command       :           Meaning
  • ls :   list (show) files and directories
  • ls -a :   list all files and directories (including those whose names begin with a dot). Files beginning with a dot (.) are known as hidden files and usually contain important program configuration information. They are hidden because you should not change them unless you are very familiar with UNIX!!!
  • mkdir :   make a directory
  • cd directory :   change to NAMED directory - i.e: cd Documents
  • cd :   change to home-directory = change to root i.e: /
  • cd ~ :   change to home-directory
  • cd .. :   change to parent directory = go back 1 directory  AND only 1 dot (.) means current directory
  • pwd (print working directory) :   display the path of the current directory = show in which directory you are.