Part II

Learning Linux Basics

Hour

4. Reading and Navigation Commands
5. Manipulation and Searching Commands
6. Using the Shell
7. Using the X Window System
8. Exploring Other X11 Window Managers

Hour 4

Reading and Navigation
Commands

This hour introduces you to the basic Linux commands you'll use for navigating, searching, and reading files and directories of your file system (the directories of your Linux partition). After working through the material, you should know how to get help on commands, find out where you are in Linux, and how to find files on your hard drive. The hour starts with navigating and searching your directory, and moves on to show you how to read directories and files. But first, you'll learn how to help yourself with the man command.

Getting Help with the man Command

One of the first things to know about Linux is that help is never far away. Like most implementations of UNIX, your Linux distribution comes with manual pages for nearly each utility, command, or programming system call. You can get information about nearly any command, including man, by typing

# man man

Manual pages started out in UNIX as one-page descriptions, available on-line, usually under the /usr/man directory. The file for each manual page is named

with a single-digit extension, and placed in a subdirectory under /usr/man. For example, the manual page for man would be named and found as

/usr/man/man1/man.1

If you want to understand the format and placement of manual pages, you won't find this information in man.1, but in man.7 under /usr/man/man7. If you look at Table 4.1, you'll see the locations and contents of each manual section.

Table 4.1. The Linux manual sections.

Each manual page traditionally has a number of sections, with the documentation for the command broken down into sections. Look at Table 4.2 for the organization of a manual page.

Table 4.2. Organization of a manual page.

Online manual pages contain special typesetting codes for the nroff text formatting program (see Hour 15, "Preparing Documents"), using special macros (as documented in man.7). This format is critically important for other programs, such as makewhatis, whatis, and apropos, which you'll learn about later in this chapter.

You can also find more detailed documentation for Linux commands and other subjects under the /usr/doc directory, which contains files called Frequently Asked Questions, or FAQs, and HOWTOs, or How-To documents. Additionally, the Free Software Foundation, which releases the GNU software packages (many of the commands discussed in this book are GNU programs), puts much of its documentation in a special hypertext "info" format.

The man command normally searches for manual pages according to instructions detailed in the man.config file under the /etc directory. These instructions define the default directories in which to look for manual pages, and they match the directories to the $MANPATH environment variable, an abbreviated string of characters defined when you first start Linux and log in. Environment variables are discussed in Hour 6, "Using the Shell." The default places to look for these pages are

MANPATH /usr/man

MANPATH /usr/local/man

MANPATH /usr/X11R6/man

MANPATH /usr/lib/perl5/man

Navigating and Searching the File System

This section introduces you to the basic navigation commands, and shows you how to move around your Linux file system, find files, and build file information databases, such as those for use with the whatis command. You'll also learn about alternative approaches and programs, and how to speed up searches to find files quickly.

Moving to Different Directories with the cd Command

The cd (change directory) command is the basic navigation tool for moving your current location to different parts of the Linux file system. You can move directly to a directory by typing the command, followed by a pathname or directory. For example, the following command will move you to the /usr/bin directory:

# cd /usr/bin

When you're in that directory, you can move up to the /usr directory with the following command:

# cd ..

You could also move to the root directory, or /, while in the /usr/bin directory by using the following command:

# cd ../..

Finally, you can always go back to your home directory (where your files are) by using either of the following commands:

# cd

or

# cd ~

Note that if you try to use the man command to read the cd man page, you won't find one. Why? Because cd is built into the shell. See bash in Hour 6, for more details.

Knowing Where You Are with the pwd Command

The pwd (print working directory) command tells you where you are, and prints the working (current) directory. For example, if you execute

# cd /usr/bin

and then type

# pwd