A very useful command
echo is used to display one or more lines of text
displays Hello, World!
-e → enables interpretation of backslash escapes
-n → disables new line
it escapes special characters
-E → forces backslash interpretation
you can use it as a calculator by adding $(())
it calculates the result of 2*6 and prints it on the screen
prints everything in the directory
prints all files/directories starting with d
prints all files/directories ending with 1
prints all directories between kronos and d2 directories
prints user's home directory
prints the $USER variable
use printenv to display all the OS variables