hichamov's Blog

To use Linux--or any Unix-like system, for that matter--you need to know a few things about shells. A shell is a program that acts as an intermediary between you and the guts of the operating system. In a DOS environment, command.com acts as your shell. Linux shells have more interesting names (like bash, pdksh, and tcsh), but they do pretty much the same thing. In addition to translating your commands into something the kernel can understand and act upon, the shell adds some important functions that the base operating system doesn't supply.

Using a Linux shell means working with a command line, which is much like working from a DOS prompt. Modern version of Linux come with graphical user interface (GUI) but some Linux tasks can only be done from the command line. The knowledge of how Linux works that you'll gain in this section will provide the foundation you need to use Linux successfully and efficiently. Here's a description of the basic features of all Linux shells, a preview of the functions they perform, and a rundown of what you'll learn in this section.

Prompts A prompt is a character or string of characters (such as $ or #) that the shell displays when it is ready to receive a new command. You'll learn about the different types of prompts and how to customize them to suit you and the way you work.

Command resolution When you enter a command, the shell must determine which program to run in order to perform that command. You'll learn how shells do this and how to change the command resolution process to suit your needs.

Job control Linux lets you multitask (run more than one command at a time). You'll learn how to start, list, and stop tasks; you'll also learn the difference between foreground and background task execution.

Command history and completion When you're entering lots of commands, sometimes you want to repeat the previous command or issue a similar one. You'll learn how to recall and modify previously entered commands, as well as find out about some keyboard shortcuts that can automatically complete your commands for you.

Wildcards and aliases Wildcards let you process a whole bunch of files at once, instead of having to repeat the same command for each file. You'll learn how to use two types of wildcards and how to create aliases for commonly used commands.

Piping and I/O redirection Sending the output of one program directly to another program or to a file can save you time and keystrokes. You'll learn how to pipe program output (connect programs together) and how to make a program get its input from a file instead of the keyboard.

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