Linux Shells by Example

11.1. Steps in Creating a Shell Script

A shell script is normally written in an editor and consists of commands interspersed with comments. Comments are preceded by a pound sign and consist of text used to document what is going on.

11.1.1. The First Line

At the top left corner, the line preceded by #! (often called "shbang") indicates the program that will be executing the lines in the script. This line is commonly:

#!/bin/tcsh

The #! is called a magic number and is used by the kernel to identify the program that should be interpreting the lines in the script. When a program is loaded into memory, the kernel will examine the first line. If the first line is binary data, the program will be executed as a compiled program; if the first line ...