Andrew Hudson - Fedora™ Unleashed, 2008 edition

$ cd ..

To return to one's home directory from anywhere in the Linux file system, use the cd command like this:

$ cd

You can also use the $HOMEshell environment variable to accomplish the same thing. Type this command and press Enter to return to your home directory:

$ cd $HOME

You can accomplish the same thing by using the tilde (~) like this:

$ cd ~

Don't forget the pwdcommand to remind you where you are within the file system!

Another important command to use is the ls command, which lists the contents of the current directory. It's commonly used by itself, but a number of options (or switches) available for ls give you more information. For instance, the following command returns a listing of all the files and directories within the current directory, including any hidden files (denoted by a . prefix) as well as a full listing, so it will include details such as the permissions, owner and group, size, and last modified time and date:

$ ls -al

You can also issue the following command:

$ ls -R

This command scans and lists all the contents of the subdirectories of the current directory. This might be a lot of information, so you might want to redirect the output to a text file so that you can browse through it at your leisure by using the following:

$ ls alR > listing.txt

Table 4.1 shows some of the standard directories found in Fedora.

TABLE 4.1 Basic Linux Directories

Some of the important directories in Table 4.1, such as those containing user and root commands or system configuration files, are discussed in the following sections. You use and edit files under these directories when you use Fedora.

Linux also includes a number of GNU commands you can use to search the file system. These include the following:

► whereis command—Returns the location of the command and its man page.

► whatis command— Returns a one-line synopsis from the command's man page.

► locate file command— Returns locations of all matching file(s); an extremely fast method of searching your system because locate searches a database containing an index of all files on your system. However, this database (about 4MB in size and named slocate.db, under the /var/lib/slocatedirectory) is built daily at 4:20 a.m. by default, and does not contain pathnames to files created during the workday or in the evening. If you do not keep your machine on constantly, you can run the updatedbcommand as the super user to manually start the building of the database.

► apropos subject command— Returns a list of commands related to subject.

Managing files in your home directory involves using one or more easily remembered commands. If you have any familiarity with the now-ancient DOS, you recognize some of these commands (although their names differ from those you remember). Basic file management operations include paging (reading), moving, renaming, copying, searching, and deleting files and directories. These commands include the following:

► cat filename — Outputs contents of filename to display

► less filename — Allows scrolling while reading contents of filename

► mv file1 file2 — Renames file1 to file2

► mv file dir — Moves file to specified directory

► cp file1 file2 — Copies file1 and creates file2

► rm file — Deletes file

► rmdir dir — Deletes directory (if empty)

► grep string file(s) — Searches through files(s) and displays lines containing matching string

Note that each of these commands can be used with pattern-matching strings known as wildcards or expressions . For example, to delete all files in the current directory beginning with the letters abc, you can use an expression beginning with the first three letters of the desired filenames. An asterisk (*) is then appended to match all these files. Use a command line with the rm command like this:

$ rm abc*

Linux shells recognize many types of filenaming wildcards, but this is different from the capabilities of Linux commands supporting the use of more complex expressions. You learn more about using wildcards in Chapter 11, "Automating Tasks."

Learn more about using expressions by reading the exor grepmanual pages.

Another file management operation is compression and decompression of files, or the creation, listing, and expansion of file and directory archives. Linux distributions usually include several compression utilities you can use to create, compress, expand, or list the contents of compressed files and archives. These commands include the following:

► bunzip2 — Expands a compressed file

► bzip2 — Compresses or expands files and directories

► gunzip — Expands a compressed file

► gzip — Compresses or expands files and directories

► shar file — Creates a shell archive of files