Linux Basic Tutorials Part - 8

UNIX/Linux Tutorial 

UNIX Variables

Variables are a way of passing information from the shell to programs when you run them. Programs look "in the environment" for particular variables and if they are found will use the values stored. Some are set by the system, others by you, yet others by the shell, or any program that loads another program. 

Standard UNIX variables are split into two categories, environment variables and shell variables. In broad terms, shell variables apply only to the current instance of the shell and are used to set short-term working conditions; environment variables have a farther reaching significance, and those set at login are valid for the duration of the session. By convention, environment variables have UPPER CASE and shell variables have lower case names.

Linux Basic Tutorials Part - 7

UNIX/Linux Tutorial

Other useful UNIX commands  

quota

All students are allocated a certain amount of disk space on the file system for their personal files, usually about 100Mb. If you go over your quota, you are given 7 days to remove excess files.

To check your current quota and how much of it you have used, type

% quota -v

Linux Basic Tutorials Part - 6

UNIX/Linux Tutorial 

File system security (access rights)

In your unixstuff directory, type

% ls -l (l for long listing!)

You will see that you now get lots of details about the contents of your directory, similar to the example below.

Each file (and directory) has associated access rights, which may be found by typing ls -l. Also, ls -lg gives additional information as to which group owns the file (beng95 in the following example):

-rwxrw-r-- 1 ee51ab beng95 2450 Sept29 11:52 file1

In the left-hand column is a 10 symbol string consisting of the symbols d, r, w, x, -, and, occasionally, s or S. If d is present, it will be at the left hand end of the string, and indicates a directory: otherwise - will be the starting symbol of the string. 

Linux Basic Tutorial Part - 5

UNIX/Linux Tutorial

Wildcards

The * wildcard

The character * is called a wildcard, and will match against none or more character(s) in a file (or directory) name. For example, in your unixstuff directory, type

% ls list*

This will list all files in the current directory starting with list....

Try typing

% ls *list

This will list all files in the current directory ending with ....list

Linux Basic Tutorials Part -4

UNIX/Linux Tutorial 

Redirection  

Most processes initiated by UNIX commands write to the standard output (that is, they write to the terminal screen), and many take their input from the standard input (that is, they read it from the keyboard). There is also the standard error, where processes write their error messages, by default, to the terminal screen.

We have already seen one use of the cat command to write the contents of a file to the screen.

Linux Basic Tutorials Part - 3

UNIX/Linux Commands

 Copying Files

cp (copy)

cp file1 file2 is the command which makes a copy of file1 in the current working directory and calls it file2 

What we are going to do now, is to take a file stored in an open access area of the file system, and use the cp command to copy it to your unixstuff directory.

First, cd to your test directory.

% cd ~/unixstuff

Then at the UNIX prompt, type,

% cp /vol/examples/tutorial/science.txt .

Note: Don't forget the dot . at the end. Remember, in UNIX, the dot means the current directory.

The above command means copy the file science.txt to the current directory, keeping the name the same.

(Note: The directory /vol/examples/tutorial/ is an area to which everyone in the school has read and copy access.

Linux Basic Tutorials Part - 2

After looking on Open Source and GNU . We look around basic command of the Linux/Unix.

1.1 Listing files and directories

ls (list)

When you first login, your current working directory is your home directory. Your home directory has the same name as your user-name, for example, john123, and it is where your personal files and subdirectories are saved.

To find out what is in your home directory, type

% ls

The ls command ( lowercase L and lowercase S ) lists the contents of your current working directory.

There may be no files visible in your home directory, in which case, the UNIX prompt will be returned. Alternatively, there may already be some files inserted by the System Administrator when your account was created.

ls does not, in fact, cause all the files in your home directory to be listed, but only those ones whose name does not begin with a dot (.) Files beginning with a dot (.) are known as hidden files and usually contain important program configuration information. They are hidden because you should not change them unless you are very familiar with UNIX!!!

To list all files in your home directory including those whose names begin with a dot, type

% ls -a

As you can see, ls -a lists files that are normally hidden.

ls is an example of a command which can take options: -a is an example of an option. The options change the behaviour of the command. There are online manual pages that tell you which options a particular command can take, and how each option modifies the behaviour of the command. (See later in this tutorial) 

Linux Basic Tutorials Part - 1

Welcomes you all to New and exciting world of Linux. Most used operating system by modern servers, super-computers and desktops. Now I am here to help to understand basic of Linux.

Open Source & GNU Foundation

Starting Linux before we learn some technologies and concepts behind it. Let's look about Open source and GNU Foundation.

Open source is an approach to the design, development, and distribution of software, offering practical accessibility to a software's source code. Some consider open source as one of various possible design approaches, while others consider it a critical strategic element of their operations. Before open source became widely adopted, developers and producers used a variety of phrases to describe the concept; the term open source gained popularity with the rise of the Internet, which provided access to diverse production models, communication paths, and interactive communities.

Software development costs in organizations have been touted as being approximately 15% of total costs. This indicates that the value of one over another development methodology is more of a marketing decision (which customers and pricing models) as much as it is about the design of software. The open source model of operation and decision making allows concurrent input of different agendas, approaches and priorities, and differs from the more closed, centralized models of development The principles and practices are commonly applied to the peer production development of source code for software that is made available for public collaboration. The result of this peer-based collaboration is usually released as open-source software, however, open source methods are increasingly being applied in other fields of endeavour, such as biotechnology 

The Open Source Definition is used by the Open Source Initiative to determine whether or not a software license can be considered open source.