UNIX COMMANDS TUTORIAL

Introduction:
In this post I am introducing UNIX Commands 
for UNIX Beginners who need details of commands
that are likely to be of to use them. UNIX is a 
Computer Operating System.This OS has backbone
of the Internet especially for large servers.This is
a free version of UNIX called as linux . This linux
has most popular OS which is used by major software
organisations for good performance.Unix was developed
around in 1969 at AT & T  labs by Dennis Ritche and 
ken Thompson.why unix has rapidly growing in the
 industry means it has the capability to take activities
 from multiple user at the same time. 


Here are the some essential commands in order to get start with UNIX.

CD: change directory
It is used to change from one  directory to another

Ex: 
cd lucky

Here will change the directory from current to lucky directory. 
ls

When ever you  log in your current working directory  is home directory. so to find out list of all files in your home directory you need to write this command.

Ex: 
% ls

 ls -a 

This command is used when you want show list of all  files whose names begin with a dot in current directory.

Ex:

% ls -a

Note:  Here -a is an option. option changes the behavior of command.


ls -l

This command is used to list of all the file names,permissions etc.. in long format.


mkdir

This command is used to create new directory.suppose you have home directory,In that home directory you can create sub directory(new directory) to place all your list of files.

Ex:

% mkdir lucky (here we create new directory with name lucky)

To see all your content in the lucky directory which command you will used?

Ans:  % ls (Got it )

pwd(print working directory)

This command is used  to find out to absolute path name of your home directory.

EX:

% pwd

The full path name will look like this:

/home/programs/core/lucky

cp(copy)

This command is used to copy a file,if you want copy old file in your a current directory file named as new file.

cp oldfile newfile

I will give example how to copy file, I have a directory named as lucky then write

% cd  ~/lucky

Then your write immediately on unix prompt,

% cp examples/core/books.txt .

NOTE: At the end you must specify .  that means your current directory

 Mv:(move)

This command is used to move files from one directory to another directory.It can also be used rename a file,by moving the file to  the same directory,but giving different names.

mv oldfile newfile

This command will rename oldfile to newfile


rm(remove),rmdir(remove directory):

This command is used to delete(remove)a file.

suppose you have file named with  books.txt then you to write the command like this

% rm books.txt(here delete file named with books.txt)


If we want create directory we use mkdir command ,to delete directory we use rmdir.

Ex:
% rmdir lucky


Note: make sure  the directory is empty before deleting directory

clear:

This command is used to clear the terminal window of previous commands before you start next section.

Ex:

% clear

 cat(concatenate)

This command is used to display the contents of the files on the screen.
Suppose if you want to see books.txt file content, then you have to type like this

% cat books.txt


 head

This command is used to see first 10 lines of a file on the screen.Before checking this command clear the screen first then check it.

Ex:  % head books.txt


 tail

This command is used to writes the last ten lines of a file to the screen.

Ex:  % tail books.txt

Grep

This command is used to search files for specified words or patterns.

% grep  java books.txt 

In above command grep has printed out each line containing the word java

grep is case sensitive; so be careful about it since Java and java is difference.

Wc(word count)

This command is used to count the words in your file.

Ex:

% wc -w  books.txt


To find home many lines the file has,then type

% wc -l books.txt


sort

This command is used to sort the lines of files or file in Ascending order.

Example

Suppose, you have a file named with books.txt, 

java
dbms
c
artificial intelligence
python
big data

if you run this books.txt file with sort command then result look like this:

% sort books.txt

artificial intelligence
big data
c
dbms
java
python

vi

This command is used  to launches a vi sual editor.To edit a file type.
In all Unix version the default editor is vi editor.If you want write characters you will need to hit i to be in insert mode and then start typing. some options for insert mode

• A appends the text at the end of the line
• a appends the text after cursor
• O open a new line of text above cursor
• o open a new line of the text below cursor

For command mode

• yy to copy a line to buffer
• p to paste text from buffer
• x to delete a single character
• ndd to delete n number of lines
• dd to delete entire line
• nyy copy n number  of line to buffer
• $ to move end of the line
• lG to go to the first line of the file
• /string to search string in a file
• n to search for next occurrence of a file