TERMINAL and common commands

HOW TO WORK ON TERMINAL

When we talk about Linux, then first thing comes in our mind is that- how to work and where to work?

Usually, we operate a Linux-based system through a Command Line Interface (CLI) or a Graphical User Interface (GUI). We usually interact with a modern UNIX shell using a Command Line Interface known as TERMINAL EMULATOR Window or some separate Virtual Console. Common terminals as we know already are- xterm and GNOME Terminal.

WHAT IS A TERMINAL?

Terminal is the graphical platform where the commands can be executed. There are various other terminals used in different Linux-based System. Commands tell the operating system to perform set of operations. All these commands are going to be written in a command line interface i.e. Terminal.

When we log into a terminal then we see some text written in the terminal window as: user_name@linux_machine_name:_~current_path$

          Keertendra@keertendra-virtual-machine:_~$

In Linux system, there is one special user for administrator, which has all permissions and access to all files. This user is known as “SUPER USER” or “ROOT”. The Dollar sign “$” indicates that we are not the root user and the path starts with a symbol “_~”, which corresponds to “/home/user_directory/”. User is also having his own directory known as Home Directory. For example:

Keertendra@keertendra-virtual-machine:_~/Desktop/Linux_Programs$

Now to login as Super User or root, we have to use a command “sudo su” then it will ask for the password, type the correct password and we will successfully logged in as root/ Super User. It can e verified by Pound sign “#” instead of Dollar sign “$”. Now the path is shown from the root “/” directory. For example:

root@keertendra-virtual-machine:/home/keertendra#

HOW TO USE COMMANDS?

Commands are the set of key words and arguments which are used to perform some specified operation. In Linux-based System, there are a numerous commands to perform various tasks. These commands are written according to a specified syntax.

SYNTAX:COMMAND_NAME   [-OPTIONS]   ARGUMENTS

COMMAND_NAME: indicates the name of the respective command say, help, man, ls, cd, etc.

[-OPTIONS]: Options are used to perform the operation on the selected item in selected manner. The square brackets “[ ]” shows that the use of options in the command is optional. It starts with a hyphen sign (-).

ARGUMENTS: arguments can be any value passed to the command to execute an operation. The operation is to be performed on the arguments. It can be file name, path, text, etc.

**** The Linux is Case- Sensitive. The Command_name, Options and Arguments are separated by a SPACE (“ “) in between.

For example: a command List command (ls) is used here to show details of all the files and folder of the Linux_Programs directory as-

$ ls –l Desktop/Linux_Programs/

WHAT ARE OPTIONS?

The command options are used in the command. Some of the common command options used in LINUX are given below:

-a: it lists all the files and directories, even hidden ones which are preceded by (“.”)

 -l: lists the size, creation date and permissions about all the files and directories in the current directory

 -d: lists the directory

 -c: don’t create file if it already present

 -f: force

 -k: block Size

 -R: recursive

 -t: type

 -V: version.

SOME CONTROL KEYS:

Control Keys performs special function. The control keys used in LINUX are:

Ctrl+S (^S)   : Pause Display

Ctrl+Q (^Q)   : Restart Display

Ctrl+C (^C)    : Cancel Operation

Ctrl+U (^U)    : Cancel Line

Ctrl+D (^D)    : Signal end of file

Ctrl+V (^V)     : Treat control character as normal character

SOME BASIC COMMANDS:

1.    GENERAL PURPOSE UTILITY COMMAND:

MAN, RESET, CLEAR, CAL, DATE, ECHO, PRINTF, BC, XCAL, EXIT etc.

2.    USER LOGIN AND PASSWORD COMMANDS:

SUDO, SU, PASSWD, WHO, WHO AM I, WHOAMI, USERADD, USERDEL, MOUNT, UMOUNT, DF, SHUTDOWN, etc.

3.    FILE COMMANDS:

ls, pwd, cd, TOUCH, mkdir, rmdir, cp, mv, rm, etc.

4.    FILE DISPLAYING COMMANDS:

CAT, TAC, MORE / LESS, etc.

5.    FILE PERMISSION COMMANDS:

CHMOD, CHOWN, etc.

6.    FILTER COMMANDS:

GREP, FIND, LOCATE, PIPE, TEE, HEAD, TAIL, WC, CMP, COMM, SORT, PASTE, CUT, etc.

7.    PROCESS MANAGEMENT COMMANDS:

KILL, KILLALL, PS, TOP, etc.

8.    COMPRESSING & ARCHIVING COMMANDS:

GZIP/ GUNZIP, ZIP/ UNZIP, TAR, etc.

****if there comes any difficulty in using any command then see the MANUAL of that respective command by using a command i.e. “man”. We can also use “help” command and “info” commands as well.

For example: to open the manual entry of command “chmod”.

                $ man chmod

For example: to get help on the command i.e. “cd”

                $ help cd

For example: to get information about the command i.e. “mkdir”

                $ info mkdir

Ok, this is little bit sufficient for terminal commands and their usage.