General assignment of values

As we already saw, Bash understands many different kinds of variables or parameters. Thus far, we haven't bothered much with what kind of variables we assigned, so our variables could hold any value that we assigned to them. A simple command line example demonstrates this:

[bob in ~] VARIABLE=12

[bob in ~] echo $VARIABLE
12

[bob in ~] VARIABLE=string

[bob in ~] echo $VARIABLE
string

There are cases when you want to avoid this kind of behavior, for instance when handling telephone and other numbers. Apart from integers and variables, you may also want to specify a variable that is a constant. This is often done at the beginning of a script, when the value of the constant is declared. After that, there are only references to the constant variable name, so that when the constant needs to be changed, it only has to be done once. A variable may also be a series of variables of any type, a so-called array of variables (VAR0VAR1, VAR2, ... VARN).