Showing posts with label OS. Show all posts
Showing posts with label OS. Show all posts

Basic Commands for Unix

 Hello friends, Here I am going to explain you all the basic command for the Unix. So you can handle system or access the data through the terminal.

       Commands :


>>Basic Commands


1)  cal : 

The cal command is used to to display the calender.
For example to check calendar you need to type cal command as follows:

               

2) passwd

The passwd command is used to change the password of the unix system. Every unix system will require a password for the security.





3) whoami, who, user

The who am i  command is used to know the name of the user by which you are currently logged in.
The who command is used to know the name of the user who are online on connected system.
The user will display the name of the users.



                                >> File Management Commands<<

4) ls command

The ls command is used to list the directories and files of the current running directory with the 
-l option.
As shown below example d stands for the directory and - is for the executable file like text file, image or any other format.




5) cat

The cat command is used to read the file. We can also create the file with the cat command by using >  sign with it. as seen below example :




6) wc (word count) command

The wc command is used to count the number of characters, words and lines of any file.
In wc  command -c for character, -w for word count and -l for line count

Syntax  $wc <filename>





7) cp command

To make a copy of a file use the cp command. The basic syntax of the command is:

Syntax :
                  $ cp source_file destination_file





8) mv Command 

The mv command is used to rename the filename

Syntax :
                 $ mv old_file new_file




9) rm Command 

The rm command is used to remove the particular file.
It is recommended to use -i option along with rm command.

Syntax :
               rm <filename>




Kernal : The Heart of OS



             The KERNAL was initially written for the Commodore PET by John Feagans, who introduced the idea of separating the BASIC routines from the operating system. It was further developed by several people, notably Robert Russell added many of the features for the VIC-20 and the C64.
             In computing Kernal is the main component of most operating system. The kernal also known as the heart of an OS.It is working as a bridge between the application and the actual data processing done at the hardware level.
            As a collection of programs written in 'C language'  that directly interact with hardware and most of manages the task like memory management , task scheduling, process management, Device management and file management, etc ....but the kernal is a program that constitutes the central core of the computer OS.It has complete control over everything that occurs in the system.
           When the system starts, the kernal is being first loaded into the memory during the boot time and it should be remains their for the entire duration of the computer session, because the services of the kernal requires continuously. The kernal is the part of OS which is responsible for all other operations.
           Unix kernal is directly above the hardware kernal manages all hardware  devices and controls programs run on the computer it is loaded into the memory when system is booted.

How Kernal works?


          When a computer boots up, it goes through some initialization functions (Like Memory checking). Then it loads the kernal and switch the control to it. Then the kernal starts up  all the required processes needed to communicate with the user and the rest of the environment (e.g. LAN).
          The kernal itself does not interact  directly with the user but rather interacts with the shell and other programs as well as with the hardware device on the system including the CPU, Memory and Disk drive.
A kernal can be contrasted with a, which is the program that interacts with user commands.