Linux

Linux is an opensource operating system.The kernel of this operating system is written by Linus Torvalds.

Basic Commands:

1. pwd:

   This command returns the present working directory as output.

   Syntax:- pwd

   Example:

   [user1@node1~] $pwd

   /users/home/user1

2. ls :

   This command lists the files and directories under the present working directory.

   Syntax: ls -[options]

   Example:

   [user1@node1~]$ls

   bin dev tmp usr

   It can be used with multiple options:

   l - lists in longname

   a - lists all files including hidden files

   R - lists all subdirectories recursively.

   r - lists files in reverse chronological order

   t - lists latest files by modification time

   h- lists all files and directories in human-readable format

3. <command> --help

   This gives a brief documentation of the command.

   Example:- $ls --help

4. grep

   This command is used to search pattern in file

   Syntax: grep -[option] pattern file_path

   Example:

   [user1@node1~]$ grep passed /root/tmp/certificate.pdf

   has passed the examination of

   It can be used with multiple options:

   -i: Ignores the case

   -v: Excludes the pattern found

   -E: Extended grep - Regular expressions can be used with patterns

5. whoami

   This command outputs the username of current user logged in

   Example:

   [user1@node1~]$whoami

   user1