It is possible to pass options from the command line or from another shell script to your shell program.
These options are supplied to the shell program by Linux as positional parameters, which have special names provided by the system. The first parameter is stored in a variable called 1 (number 1) and can be accessed by using $1 within the program. The second parameter is stored in a variable called 2 and can be accessed by using $2 within the program, and so on. One or more of the higher numbered positional parameters can be omitted while you're invoking a shell program.
Understanding how to use these positional parameters and how to access and use variables retrieved from the command line is necessary when developing more advanced shell programs.
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