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256 Managing Files and Directories

than the command interpreters of the day.

Enter the Bourne shell (known simply as sh), created by S.R. Bourne, which fulﬁlled the goals of

UNIX’s creators.

Since the creation of the Bourne shell, other shells have been developed, such as the C shell (csh)

and the Korn shell (ksh).

When the Free Software Foundation sought a royalty-free shell, developers began to work on the

language behind the Bourne shell as well as some of the popular features from other shells available

at the time.

The result was the Bourne Again Shell – or bash.

By now, of course, you’ve probably seen the word bash when you’ve mistyped commands at the

shell prompt (as in bash: oops: command not found).

In Chapter 16 on page 217, when we covered redirection and piping, we were also demonstrating the

power of bash.

Tip: You can learn more about bash by reading the bash man page. At the shell

prompt, type man bash (or you can save the ﬁle as a text ﬁle by typing man bash |

col -b > bash.txt, which you can then open to read with an editor like pico or a

pager like less.Youcanalsoprinttheﬁle with man bash | col -b | lpr,butbe

warned: it’salargeﬁle. If you want more information, O’Reilly & Associates publishes

Learning the bash Shell, by Cameron Newham and Bill Rosenblatt.

Although your system came with several different shells, bash is the default shell for Red Hat Linux.

You might think of bash as a ﬂeet-footed ofﬁce assistant who has made a habit of keeping notes on

ways to fulﬁll commands quickly. This assistant also keeps pointers on how you like to customize

the way you work.

These “pointers” bash keeps are referred to as environment variables.

The shell uses an “environment” in the same way we use an environment, like a kitchen. We work

in our kitchen, arrange pots, pans, and spices. We know where the dishes are, how things operate.

Thesamecanbesaidforbash and its environment. There’s a basic arrangement to bash as there

would be to just about any kitchen. For example, we’d expect to see pots in a kitchen in the same

way that we would expect to see certain commands in bash.

That’s the idea behind environment variables.

As long as your assistant has the right pointers, he’ll fulﬁll your commands quickly.

Let’s take a look at our environment variables. At the shell prompt, type:

env

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Brak uwag

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