Sams Teach Yourself Shell Programming in 24 Hours, Second Edition

Parameters and Variables

This section describes parameters and variables.

User-Defined Variables

Any variable defined by a programmer is a user defined variable. User-defined variable names

• Must start with letters

• Can contain only letters or digits

• Are often in capital letters to differentiate them from UNIX commands

Variables are assigned values using the assignment operator, =, as follows:

							VAR=value
						

Here, VAR is the name of the variable and value is the value you want to assign to it.

Variables are unset using the unset command as follows:

unset var1 ... varN
						

Here var1 … varN are the names of the variables to unset.

Variable Substitution

The value stored in a variable can be accessed using the $ operator as follows:

$VAR
							

Here VAR is the ...