The Shell Script Of Linux
The GNU/Linux shell is a special interactive utility. It provides a way for users to start programs, manage files on the filesystem, and manage processes running on the Linux system. The core of the shell is the command prompt. The command prompt is the interactive part of the shell. It allows you to enter text commands, and then it interprets the commands and executes them in the kernel.
The shell contains a set of internal commands that you use to control things such as copying files, moving files, renaming files, displaying the programs currently running on the system, and stopping programs running on the system. Besides the internal commands, the shell also allows you to enter the name of a program at the command prompt. The shell passes the program name off to the kernel to start it.
You can also group shell commands into files to execute as a program. Those files are called shell scripts. Any command that you can execute from the command line can be placed in a shell script and run as a group of commands. This provides great flexibility in creating utilities for commonly run commands, or processes that require several commands grouped together.
There are quite a few Linux shells available to use on a Linux system. Different shells have different characteristics, some being more useful for creating scripts and some being more useful for managing processes. The default shell used in all Linux distributions is the bash shell. The bash shell was developed by the GNU project as a replacement for the standard Unix shell, called the Bourne shell (after its creator). The bash shell name is a play on this wording, referred to as the “Bourne again shell.”
In addition to the bash shell, we will cover several other popular shells in this book. Table 1.2 lists the different shells we will examine.
Most Linux distributions include more than one shell, although usually they pick one of them to be the default. If your Linux distribution includes multiple shells, feel free to experiment with different shells and see which one fits your needs.
The shell contains a set of internal commands that you use to control things such as copying files, moving files, renaming files, displaying the programs currently running on the system, and stopping programs running on the system. Besides the internal commands, the shell also allows you to enter the name of a program at the command prompt. The shell passes the program name off to the kernel to start it.
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| The Shell Script Of Linux |
You can also group shell commands into files to execute as a program. Those files are called shell scripts. Any command that you can execute from the command line can be placed in a shell script and run as a group of commands. This provides great flexibility in creating utilities for commonly run commands, or processes that require several commands grouped together.
There are quite a few Linux shells available to use on a Linux system. Different shells have different characteristics, some being more useful for creating scripts and some being more useful for managing processes. The default shell used in all Linux distributions is the bash shell. The bash shell was developed by the GNU project as a replacement for the standard Unix shell, called the Bourne shell (after its creator). The bash shell name is a play on this wording, referred to as the “Bourne again shell.”
In addition to the bash shell, we will cover several other popular shells in this book. Table 1.2 lists the different shells we will examine.
| Shell | Description |
| ash : | A simple, lightweight shell that runs in low-memory environments but has full compatibility with the bash shell |
| korn : | A programming shell compatible with the Bourne shell but supporting advanced programming features like associative arrays and floating-point arithmetic |
| tcsh : | A shell that incorporates elements from the C programming language into shell scripts |
| zsh : | An advanced shell that incorporates features from bash, tcsh, and korn, providing advanced programming features, shared history files, and themed prompts |
Most Linux distributions include more than one shell, although usually they pick one of them to be the default. If your Linux distribution includes multiple shells, feel free to experiment with different shells and see which one fits your needs.
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