Typing Unix Commands

Steven J Zeil

Old Dominion University Dept. of Computer Science

Jan. 26, 2007

Contents:

1 Command Arguments

2 Special Characters

3 One Pattern, Many Instances

3.1 Wild Cards

3.2 Regular Expressions

4 Quoting

(A printable version of this document is available here.)

To run a Unix command (or any program, for that matter), you normally must type the name of the command/program file followed by any arguments. There is actually a program running that accepts your keystrokes and launches the appropriate program. The program that reads and interprets your keystrokes is called the shell. There are many shells available, all of which offer different features. The default shell for ODU CS is called tcsh, and we'll concentrate on that.

The command/program name is usually not given as a full file name. Instead, certain directories, such as /bin, are automatically searched for a program of the appropriate name. This set of directories is referred to as your “execution path” New accounts are set up so that the directories holding the most commonly used Unix commands and programs are already in the execution path.1

You can see your path by giving the command

echo $PATH

And you can modify your $PATH, if desired, to add additional directories.

Thus, one can invoke the ls command as

/bin/ls

but it's usually simpler to say