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CHAPTER 2 Unix Structure

2.4 Unix Programs

A program, or command, interacts with the kernel to provide the environment and perform the functions called for by the user. A program can be: an executable shell file, known as a shell script; a built-in shell command; or a source compiled, object code file.

The shell is a command line interpreter. The user interacts with the kernel through the shell. You can write ASCII (text) scripts to be acted upon by a shell.

System programs are usually binary, having been compiled from C source code. These are located in places like /bin, /usr/bin, /usr/local/bin, /usr/ucb, etc. They provide the functions that you normally think of when you think of Unix. Some of these are sh, csh, date, who, more, and there are many others.

Introduction to Unix - 14 AUG 1996
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