UNIX® Shells by Example Fourth Edition

Chapter 14. Programming the Bash Shell

Introduction

When commands are executed from within a file, instead of from the command line, the file is called a shell script and the shell is running noninteractively. When the bash (Bourne Again) shell starts running noninteractively, it looks for the environment variable, BASH_ENV (ENV) and starts up the file (normally .bashrc) assigned as its value. After the BASH_ENV file has been read, the shell will start executing commands in the script.^[1]

The 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 ...