Linux Basic Commands

The command line is a text-based interface that can be used to take input from a user as an instruction to the computer system. In the Linux, the command line is provided by a program called the “shell”. There are so many shell program have been developed but “GNU Bourne-Again shell (bash)” is the default shell in some Linux distribution such as Centos and RHEL. Bash is an improved version of one of the most successful shells used on UNIX like the system the Bourne Shell (sh).

Using “bash” to execute command can be powerful. The “bash” shell provides a scripting language that can support the automation of tasks. The shell has additional capabilities that can simplify or can make some operation possible that are hard to accomplish with graphical tools.

Note: The “bash” shell is similar in concept to “cmd.exe” the command line interpreter of Microsoft Windows, although bash is a more sophisticated scripting language and it is also similar to “PowerShell”.

To access the terminal in a graphical mode of Centos and RHEL you just need to select Application > Utilities > Terminal or Just right click on an empty desktop > Open Terminal.

From the Activities Overview, select Terminal from the dash (either from the favorite’s area or by finding it with the grid button (inside utility grouping) or the search field at the top of the window overview).

Before starting to learn some commands let understand the difference between $ and #.

When a shell is used interactively. The shell displays a string when it is waiting for a command from the user. This is called the shell prompt. When a regular user starts a shell, it shows $ character to the end of the prompt by default.

The $ character gets replaced by a # if the shell is running as the superuser, root. This # character makes it more obvious that it is a superuser shell, which helps to avoid accidents and mistakes in the privileged account.

Linux Basic Commands

Let’s starts with simple Linux commands.

1. pwd command: “pwd” stands for present working directories that print the absolute path of the current working directories. 

2. cal command:  “cal” command display calendar of current month but by specifying month and year it will display a calendar of that specific month and year for example: “cal 5 2000”.

From the above example 5 stands for the month “may” and 2000 is the “year”. You can practice by specifying only a month after the “cal” command.

3. who command: “who” command displays all users who are currently logged in.

4. whoami command: “whoami” command displays the name of a current user who is logged-in into a particular terminal.

5. who am i command: There is a difference between “whoami” and “who am i” the command “who am i” display not only current user who is logged-in but also pseudo-terminal (pts), time and comment.

6. clear command: “clear” command is used to clear the current terminal.

7. date command: “date” command is used to displays the current date and time.

8. ls command: “ls” command display list of files and directories from current working directories, for example, if you are in the root directory and you type ‘ls” command then it will display all the files and directories under the root directory.

9. cd command: By using “cd” command you can change directory. For example: “cd /directory”.

10. touch command: with “touch” command you can create a file without any content. It extension can be .txt, .file, .zip, or etc. 

11. rm command: “rm” command stands for remove which is used to remove files, but not directories.

If you try to remove directory by just “rm “command it will give throw a message “cannot remove “dir”: Is a directory”.But if you want to remove directories you have to use –r (recursive) option.

12. mkdir command: when you want to make a directory then use “mkdir” to create directory and ‘mkdir” stands for make directory.

If you want to make subdirectory under a directory from a single command then use –p, this means parent option creates parent directories for the requesting destination.

13. rmdir command: To remove any directory you can use the “rmdir” command and “rmdir” stands for remove directory.

14. mv command: “mv” command is used to move files or directories from source to destination. The example for the command is “mv source destination”.

The move command can be used to rename the file or directories as well.

15. cp command: “cp” command is used to copy a file or directories from source to destination.

Useful command line-editing shortcuts

Shortcut	Description
Ctrl+l	Clear the current terminal.
Ctrl+a	Jump to the start of the command line.
Ctrl+e	Jump to the last line of the command.
Ctrl+u	Clear from the cursor to the start of the command line.
Ctrl+k	Clear from the cursor to the last line of the command.
Ctrl+left arrow	Jump to the beginning of the previous world on the command line.
Ctrl+right arrow	Jump to the end of the next word on the command line.
Ctrl+r	Search the history list of commands for a pattern.