Installation guide

108 Chapter 11. Shell Prompt Basics

Sometimes, you may accidentally open a program ﬁle or some other non-text ﬁle in a terminal window.

Once you close the ﬁle, you could ﬁnd that the text you are typing does not match the output on the

monitor.

In such cases, type reset to return the terminal window to its default values.

11.9. Manipulating Files with cat

Red Hat Linux has a 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 system.

The utility is called cat, short for concatenate, which means that it strings ﬁles together.

The command cat will also display the contents of an entire ﬁle on the screen (for example, type cat

filename.txt. If the ﬁle is fairly long, it will quickly scroll past you on the screen. To prevent this,

use the cat filename.txt | less command.

Using the pipe (|) and the less command displays the ﬁle one page at a time. You can then use the

left and right arrow keys to move back and forth through the pages. For more on pipes, see Section

11.10.

11.9.1. Using Redirection

Redirection means causing the shell to change what it considers to be standard input or where the

standard output should be going.

To redirect standard output, use the

symbol. Placing after the cat command (or after any utility or

application that writes to standard output) will direct its output to the ﬁlename following the symbol.

For example, using cat by itself simply outputs whatever you input to the screen as if it were repeating

the line you just typed. The following example shows cat repeating every line that is entered:

[sam@halloween sam]$cat

buy some sneakers

then go to the coffee shop

then buy some coffee

To redirect cat output to a ﬁle, type the following at a shell prompt (pressing the [Enter] key takes

you to the next blank line):

[sam@halloween sam]$cat

sneakers.txt

buy some sneakers

then go to the coffee shop

then buy some coffee