Variables in Shell

• In Linux (Shell), there are two types of variable:
  1. System variables - Created and maintained by Linux itself. This type of variable defined in CAPITAL LETTERS.
     • We have learned the command printenv to see environment variables. You can see system variables by giving command like some of the important System variables are:
       

       Table 3.1: Some of the important System variables

       System	Variable Meaning
       BASH	Our shell name
       BASH_VERSION	Our shell version name
       COLUMNS	No. of columns for our screen
       LINES	No. of columns for our screen
       PS1	Our prompt settings
       HOME	Our home directory
       OSTYPE	Our Os type
       PATH	Our path settings
       PWD	Our current working directory
       SHELL	Our shell name
       LOGNAME	Our logging name
       USERNAME	User name who is currently login to this PC

       
       
  2. User defined variables - Created and maintained by user. This type of variable defined in lower letters. The following script defines three variables; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/variscriptvariscript

     #
     # Script to test MY knowledge about variables!
     #
     myname=Vivek
     myos = TroubleOS
     myno=5
     echo "My name is $myname"
     echo "My os is $myos"
     echo "My number is myno, can you see this number ?"