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Chapter 11. Shell Prompt Basics 115

cat sneakrs.txt

Nothing happens, of course, because there is no sneakrs.txt ﬁle. No problem. We will just use the

up-arrow key to bring back the command, then use the left-arrow key to get to the point where we

missed the "e." Insert the letter and press [Enter] again.

We now see the contents of sneakers.txt.

By default, up to 500 commands can be stored in the bash command line history ﬁle.

Tip

By typing the env command at a shell prompt, we can see the environment variable that controls

the size of the command line history. The line which reads, HISTFILESIZE=500 shows the number of

commands that bash will store.

The command line history is actually kept in a ﬁle, called .bash_history in our login directory. We

can read it in a number of ways: by using pico, cat, less, more, and others.

Be aware that the ﬁle can be long. To read it with the more command, from your home directory type:

more .bash_history

To move forward a screen, press [Space]; to move back a screen, press [b]; to quit, press [q].

Tip

To ﬁnd a command in your history ﬁle without having to keep hitting the arrow keys or page through

the history ﬁle, use grep, a powerful search utility (see Section 11.11.3. Here is how you can quickly

ﬁnd a previously used command: say you are searching for a command that is similar to cat sneak-

something. You have used the command and you think it might be in your history ﬁle. At the shell

prompt, type:

history | grep sneak

Another time-saving tool is known as command completion. If you type part of a ﬁle, command, or

pathname and then press the [Tab] key, bash will present you with either the remaining portion of the

ﬁle/path, or a beep (if sound is enabled on your system). If you get a beep, just press [Tab] again to

obtain a list of the ﬁles/paths that match what has been typed so far.

For example, if you forget the command updatedb, but remember a portion of the command, you

can su to root, then at the shell prompt, type up, press the [Tab] key twice and you will see a list

of possible completions, including updatedb and uptime. By typing the partial command upd and

pressing [Tab] again, your command is completed for you.

11.13. Using Multiple Commands

Linux allows you to enter multiple commands at one time. The only requirement is that you separate

the commands with a semicolon (you can see an example in Figure 11-7).

Want to see how long you have been online? Just combine the date command with Mozilla’s com-

mand.

date; mozilla; date

1 2 ... 110 111 112 113 114 115 116 117 118 119 120 ... 157 158

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Red Hat NETSCAPE MANAGEMENT SYSTEM 6.1 - COMMAND-LINE Guida di Installazione Pagina 115