Chapter 3. What you need to know about running programs

You run programs in UNIX by typing them on the command line.

On a UNIX system, you run programs by typing the name of the program on the command line and pressing Return. Usually, this is all you need to know.

However, sometimes a program may not work correctly. Or it may not work at all. Maybe you’re not even sure what program you want to run.

Before you take your problem to the system administrator, you should learn something about how programs are run in UNIX. This chapter covers:

  • What to do when you can’t seem to run a command (“Command not found.”)

  • Why a program may not work properly

  • How to find out more about a program’s options and use

Users on X terminals or workstations may start programs via their graphical user interface, by selecting them from a menu, or by clicking a button. Many of the issues listed in this chapter can also apply to running programs from a GUI environment, but they may be a bit more complicated to fix. See your system administrator for information on how to properly configure your graphical user environment.

Knowing about commands

 

I don’t know a lot of commands. I only use ones I’ve been shown. I sometimes wonder what commands or options would be useful to me that I don’t even know exist.

 
 --Carol Vogt
Knowing about commands

Capitalization and spacing count

For Macintosh and PC users, it’s important to remember that UNIX commands are case-sensitive. Most commands are all lowercase. UNIX won’t “understand” a command that is capitalized differently.

If you type LS, that’s not the same as typing ls:

% LS
LS: Command not found.
% ls
mbox
personal
status
temp

Mac users can find UNIX’s command syntax puzzling. The general form is the command name, followed by any options. Options usually start with dashes. For example:

% ls -l

There is a space between a command and the options. If you type the ls command with the -l option, but forget the space between, UNIX will think the full name of the command is ls-l and won’t be able to run the command.

% ls-l ls-l: Command not found.
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