Translations by xiaocao2000

executable files can be run as a program

directories can be entered

To learn more about file permissions in Linux, read the <ulink url="https://wiki.ubuntu.com/FilePermissions">file permissions page</ulink> in the Ubuntu Wiki.

Working at the command line is not as daunting a task as you would think. There is no special knowledge needed to know how to use the command line, it is a program like everything else. Most things in Linux can be done using the command line, although there are graphical tools for most programs, sometimes they are just not enough. This is where the command line comes in handy.

The original use of the terminal was a file browser and indeed it is still used as a file browser, in the event of the graphical environment failing. You can use the terminal as a file browser to navigate your files and undo the changes that have been made.

View Directories: - ls

The <application>ls</application> (LiSt) lists files in different colors with full formatted text

Create Directories: - mkdir (directory name)

The <application>mkdir</application> (MaKeDIRectory) command will create a directory.

Change Directories: - cd (/directory/location)

The <application>cd</application> (ChangeDirectory) command will change from your current directory to any directory you specify.

Copy Files/Directories: - cp (file or directory name) (to directory or filename)

The <application>cp</application> (CoPy) command will copy any files you specify. The <application>cp -r</application> command will copy any directories you specify.

Remove Files/Directories: - rm (file or directory name)

The <application>rm</application> (ReMove) command will delete any filename you specify. The <application>rm -rf</application> command will remove any directory you specify.

Rename Files/Directories: - mv (file or directory name)

The <application>mv</application> (MoVe) command will rename/move any file or directory you specify.

Find Files/Directories: - locate (file or directory name)

The <application>locate</application> command will search your computer for any filename you specify. It uses an index of the files on your system to work quickly: to update this index run the command <application>updatedb</application>. This command is run automatically each day, if you leave your computer on. It needs to be run with administrative privileges (see <xref linkend="root-and-sudo"/>).

You can also use wildcards to match one or more files, such as "*" (for all files) or "?" (to match one character).

For a more thorough introduction to the Linux command line, please read the <ulink url="https://wiki.ubuntu.com/BasicCommands">command line introduction</ulink> on the Ubuntu wiki.

Text Editing

If you need to use a text editor from the command line, you can use <application>nano</application>, which is a simple to use text editor. When running it from the command line, always use the following command, which ensures that the editor will not introduce line breaks:<screen>nano -w</screen>

For more information about how to use <application>nano</application>, refer to the <ulink url="https://wiki.ubuntu.com/NanoHowto">guide on the wiki</ulink>.

There are also quite a few other terminal-based editors available in Ubuntu, popular ones include <application>VIM</application> and <application>Emacs</application> (the pros and cons of each are cause for much friendly debate within the Linux community). These are often more complex to use than <application>nano</application>, but are also more powerful.

Root And Sudo

The root user in GNU/Linux is the user which has administrative access to your system. Normal users do not have this access for security reasons. However, Ubuntu does not include the root user. Instead, administrative access is given to individual users, who may use the "sudo" application to perform administrative tasks. The first user account you created on your system during installation will, by default, have access to sudo. You can restrict and enable sudo access to users with the <application>Users and Groups</application> application (see <xref linkend="users-and-groups"/> for more information).

When you run an application that requires root privileges, sudo will ask you to input your normal user password. This ensures that rogue applications cannot damage your system, and serves as a reminder that you are about to perform administrative actions which require you to be careful!

To use sudo when using the command line, simply type "sudo" before the command you wish to run. Sudo will then prompt you for your password.

Sudo will remember your password for a set amount of time. This feature was designed to allow users to perform multiple administrative tasks without being asked for a password each time.

Be careful when doing administrative tasks, you might damage your system!

To use a "root" terminal, type "sudo -i" at the command line.

For more information on the <application>sudo</application> program and the absence of a root user in Ubuntu, read the <ulink url="https://wiki.ubuntu.com/RootSudo">sudo page</ulink> on the Ubuntu wiki.

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