Red Hat NETSCAPE MANAGEMENT SYSTEM 6.0 - CUSTOMIZATION User Manual download pdf (Page 248)

236 You Are Here

Summary: To clear clutter in a console or xterm window type clear;toreturnan

xterm window to its default display properties, type reset.

16.6 Using cat

There’s a handy utility which can help you keep short lists, gather those lists together and, at the

same time, show you a little of the power behind your Red Hat Linux system.

The utility is called cat,shortfor“concatenate,” which means that it strings ﬁles together.

But cat can also perform a quick demonstration of two important terms: standard input and standard

output.

Standard input and standard output direct input and output (often referred to as I/O)totheuser.If

a program reads from standard input, it will, by default be reading from the keyboard. If a program

writes to standard output, by default it will be writing to the screen.

Let’s start cat to see what this means. At the shell prompt, type:

cat

The cursor moves to a blank line. Now, in that blank line, let’stype:

stop at sneaker store

and press the

Enter key. Suddenly, your screen looks like:

[billy@localhost billy]$ cat

stop by sneaker store

To quit cat now, just move the cursor to a blank line by pressing

Enter then press the Ctrl and D

keys at the same time.

So it’s not too exciting. But cat has just demonstrated the deﬁnition of standard input and standard

output. Your input was read from the keyboard (standard input), and that input was then directed

to your terminal (standard output).

Summary: Standard input is often text which is entered from the keyboard. Standard

output is the place where information is sent, such as your terminal (as shown in Figure

16.11).

1 2 ... 243 244 245 246 247 248 249 250 251 252 253 ... 299 300

No comments

Red Hat NETSCAPE MANAGEMENT SYSTEM 6.0 - CUSTOMIZATION User Manual Page 248