Learning to Use Unix and Consulting Assistance

Some popular introductory books on Unix as well as books that document more advanced topics are listed in References.

Unix systems provide a variety of online information to provide assistance to new and experienced users. The available online assistance programs will be the subject of the remainder of this chapter.

Using the man Command

The command reference manual for most Unix systems is maintained online and may be accessed with the man(MANual) command. For the chosen command, man displays successive manual pages one at a time. After the first page is displayed, you may view the next page by pressing the space bar. You must press the space bar after each page in order to view the next page.

Syntax for the man command is:

man command_name

For example, to obtain help on the "man" command, enter:

man  man

man will continue displaying successive manual pages for the chosen command until the last page is displayed. On some systems you may go backward by pressing <b>. You may exit at any time before the last page by pressing <q>. For a listing of the commands available within man, press <h>.

The functions associated with each of the above keys takes effect immediately after the indicated key is pressed; it is not necessary to press <Return> after any of the man sub-commands. Pressing <Return>, within man, results in the screen scrolling down one line for each time the <Return> key is pressed.

On many Unix systems, you can locate a specific test string within the displayed man pages by entering a slash (/) followed by the text you wish to locate.

man will typically display the following information about each command:

PURPOSE:
provides a brief description of the function(s) performed by the command.
SYNTAX:
describes how the command is entered.
DESCRIPTION:
provides a more complete description of how the command is used.
FLAGS:
lists the options that are available for use with the command.
EXAMPLES:
illustrates some of the most common applications of the command with an example and description of the results you would expect.
FILES:
lists the files related to use of this command.
RELATED INFORMATION:
suggests references to other commands which perform similar or related functions.

Exercise: Using man to Learn about the "ls" Command

If you have not done so already, copy the sample files to your userid (see Sample Files). Then enter the following commands and observe the differences in the formatted output display resulting from each command:

ls  -F
ls  -a
ls  -l
ls  -R
ls  -laF

A dash is used to specify options to most Unix commands. The last example illustrates how more than one option may be specified when entering a command; it is not necessary to precede each option with a dash.

Now read the man pages for the ls command and pay attention to the descriptions for each of the above command flags:

man  ls

Using InfoExplorer

The "info" command is available with the AIX operating system to invoke the IBM InfoExplorer and is typically not found on other implementations of Unix. InfoExplorer enables you to access its data by a variety of paths, e.g., by task, command name, or documentation source. It is thus a powerful tool for exploring the capabilities of the AIX operating system. It is most convenient to use InfoExplorer as an X application.

After invoking the "info" command and the introductory messages are displayed, a menu panel will appear. If you have invoked InfoExplorer as an X application, you can use your mouse to make selections; otherwise, you can move between menu options using the <tab> key, press <Return> to make a selection, press<Ctrl-W> to back through your prior selections, and press <Ctrl-C> to exit.

Message of the Day

When you first logon to a Unix system a welcome message will typically be displayed. The display may also include information about recent changes to the system and the location of more detailed information regarding the significance of these changes. Some Unix administrators update their systems daily and it is important to read these messages.

If you would like to review the Message Of The Day later in your logon session, enter:

cat  /etc/motd

Local System Information: the news Command

The "news" command enables you to review the most currently posted system information. Typically you will receive notification upon logon if there is "news" waiting to be read. If so, simply enter:

news

If you have already read the most recent news, nothing will be displayed in response to this command. If you would like to reread some news that you had read previously, enter:

news  -a

If a news item is long, you may wish to pipe the output through the more command so that you can read it one page at a time:

news -a | more