If you can enter commands into the shell, you can write shell scripts. A shell script (also known as a Bourne shell script) is a series of commands written in a file; the shell reads the commands from the file just as it would if you typed them into a terminal.
11.1 Shell Script Basics
Bourne shell scripts generally start with the following line, which indicates that the
/bin/sh program should execute the commands in the script file. (Make sure that there’s no whitespace at the beginning of the script file.)
#! part is called a shebang; you’ll see it in other scripts in this book. You can ...