Training/Linux - command line
Contents
Introduction
This represents a series of teaching pages to allow you to learn more about Viper's Linux command line interface
Command Line
Like other operating systems Linux does have a window’s type environment too called X and hopefully in the future its successor Wayland. (Linux refers to X and Wayland with the term Display Server). However, with VIPER the vast majority of work will be carried out on the command line.
The command line in Linux is referred to as a shell. The shell is a program that allows the user to interact with Linux at the command line. In true Linux style there are a few different ones to choose from, however the one used predominantly is BASH. The name BASH is an acronym for “Bourne Again SHell”, a reference to BASH is an enhanced replacement for sh, the original Unix shell program written by Steve Bourne.
Man pages
This will explain the use of man pages (also called manual pages) on Linux. Most Linux files and commands have pretty good man pages to explain their use. Type man followed by a command (for which you want help) and start reading. Press q to quit the man page. See below:
user@viper:~$ man whois (shows manual page for the command whois)
user@viper:~$ man syslog.config (shows the manual page for a configuration file)
user@viper:~$ man syslogd (show the manual for a daemon (background program))
user@viper:~$ man –k syslog (an apropos which shows a list of available man pages with this string contained within it)
Working with directories
As with other operating systems such as Microsoft Windows the filesystem is based around files and directories. Linux is no exception to this and uses a number of commands for the user to navigate around its own filesystem.
This module is a brief overview of the most common commands to work with directories: pwd, cd, ls, mkdir and rmdir. These commands are available on any Linux system.
This section will also discuss absolute and relative paths and path completion in the bash shell.
pwd
On the command line pwd (or print working directory) basically displays the current directory you are in. This would appear as:
dbird@viper:~$ pwd
/home/dbird
cd
On the command line cd (or change directory) changes your current directory to the one specified:
user@viper:~$ cd /var
user@viper:~$ pwd
/var user@viper:~$ cd /home/user
user@viper:~$ pwd
/home/user
There is also a shortcut back to your home directory by typing the character ~ (tilda) which has the same effect as typing (for example) /home/user.
user@viper:~$ cd ~
user@viper:~$ pwd
/home/user
To go to the directory above (or parent directory), we use the characters ..
user@viper:~$ pwd
/home/user
user@viper:~$ cd ..
user@viper:~$ pwd
/home
There is also the character . which means the current directory. This is not useful for the cd command but is very useful for copying files to your current directory.