Some CLI Basics

From openSUSE

Introduction

A Command-Line Interface (CLI) is the traditional way to interact with an operating system. Many operating systems (even modern ones) have a CLI, such as DOS, OS/2, Windows, and Linux. A CLI mean is you type a specific commands into a command prompt to perform a specific action. Some things can only be done at a command-line and a lot of the time a command-line is quicker than the graphical way.

Legend

• ~ = users home directory
• / = Unix Delimiter symbol

How does a Linux command-line differ from a Windows command-line?

The first thing you will notice is that there is no drive letters in Linux like there are in Windows. Because Windows and DOS use drive letters, their command-line's start with the drive letter you're currently sitting on (eg. C:\> ). A Linux command-line will goto the current users home directory and will not have any drive letter. A command-line in Linux follows the user@host convention, because in a Linux based system disk drives and hard disk partitions are mounted on Linux's root partition. In normal directory's (these directory's are real directory's) and are not assigned any drive letters like each hard disk partition (and disk drive) would be in Windows.

The current directory concept

This concept is the very same in Windows, in that if for example you are currently sitting in the WINDOWS folder on drive C the command-line would look like this: C:\WINDOWS> Therefore WINDOWS is your current working directory because that's the folder (directory) you are sitting in. So you still need to remember which folder you are sitting in when using the command-line, regardless of which system you are using.

The relative and absolute path concept

Which ever folder you are currently sitting in, is the folder all commands you run will be applyed to. Let's say you are already sitting in the folder you want apply the particular command to, you would use a relative path and just type the file or folder name you want to modify in some way. An absolute path is the whole path to a file or folder, like for example the cp command's full path: /bin/cp This concept is the very same in Linux.

Command options/switches

Like in Windows, DOS as well as many other systems most Linux command-line commands have extra options one can use with them. Command options basically narrow or widen the scope of the command. In Windows and DOS (as well as many other systems) command options are usually indicated by the forward slash eg. dir/w Most Linux and Unix commands are indicated by a space and then - , for example ls -l which lists all files and folders with security permissions.

A Linux command-line (from a terminal window) and a Windows XP command-line

• A Linux terminal shell window - current working directory/folder is my home directory

• A Windows command-line - current working directory is the James folder

A table of some basic Windows and Unix/Linux commands

This is only a very small selection of commands that are available for OpenSUSE 11.x Note the extra 3rd column, the reason for that is because some commands don't exist in all Linux/Unix distributions.

Command Description	Windows Command/Program	Unix/Linux Command/Program	Unix Command common in most distros
Changes the current working folder	cd	cd
Creates folders	md, mkdir	mkdir
Copy's files and/or folders	copy, xcopy	cp
Moves files and/or folders	move	mv
Renaming files and folders	rename	mv
Delete's files and/or folders	del, rd	rm
Changes the current user account to a different user	runas	su
Adding user accounts	Windows Control Panel	useradd
Changing the system settings	regedit, Windows Control Panel	yast, yast2 (for the YaST GUI)	-- Yast is SUSE Linux distro only (OpenSUSE and SLED)
Monitoring processes	taskmgr (Task Manager)	top
Monitor your network connections	netstat	netstat

How to bring up a Linux command-line

• Press ALT+CRTL+F1 and login to the virtual terminal
• In KDE goto the K Menu (SUSE menu) > Applications > System > Terminal > Terminal Program
• In GNOME goto the GNOME Menu > Terminal

The following commands are not specific to openSUSE, therefore you will find them in most Linux/Unix distributions. Some of the following commands may also require root rights.

Some commands only have an info page or Unix manual page and not the other, so just be aware of that. But most of them have both a Unix manual page and an info page.

View Unix manual page of the command cp

Type:

View the info page for the command cp

Type:

These commands relate directly to dealing with the various files systems in use by Linux

Listing files and folders

Type:

Create a directory named mydir

Type:

Copy a file named /bin/file to your home directory

Type:

Moving ~/mydir to ~/dir2/mydir

Type:

Renaming a file named file to file1

Type:

Delete the file named ~/file

Type:

Delete a directory named mydir that contains files

Type:

Display the full path to a command

Type:

View the full contents of a file named file

Type:

View the first 10 lines of a file named file1

Type:

View the last 10 lines of a file named file1

Type:

These commands are related directly to user's and groups

Display currently logged in users

Type:

Add a user named bob

Type:

Delete a user named bob

Type:

Send a message to another user

Type:

Killing a process

Type:

get the process number from the top command

Killing a process tree

Type:

View current processes that are running

Type:

View current system runlevel

Type:

Change to runlevel 1

Type:

or

type:

Get Information About Kernel Modules

Replace module-name with the real name of kernel module, without leading path and extension, that you want to get information.

list all USB devices

Type:

list all PCI devices

Type:

This section is commands for various Linux media players and other multimedia software

Use mplayer to play an audio file named "audio.mp3"

Type:

Clear the screen

Type:

View bash history

Type:

Specific commands means that you may not find the following commands in some other Linux/Unix distributions. Some of the following commands also may require administrator rights to be run.

Install an RPM software package

Type:

or

type:

Run the command-line version of YaST

Type:

See Also

• http://en.wikipedia.org/wiki/Command-line_interface
• http://www.think-lamp.com/2008/11/very-useful-linuxunix-commands/
• http://books.google.com/books?id=OmnF5MGRNn8C&dq=in+the+beginning+comand+line&pg=PP1&ots=XTN1PFZuJw&sig=S-k5FfNtMXcbbqjqUiqSaMyII8Q&hl=en
• http://en.wikipedia.org/wiki/Shell_script
• http://en.wikipedia.org/wiki/Path_(computing)