When in doubt – Quote!

Having established that variables are a type of parameter, we should always keep this in mind, especially, when reading manuals and HOWTOs. Often the documentation refers to parameters and in doing so they include variables, as well as, the bash special parameters, such as $1 and so on. In keeping with this, we will look at why it is advisable to quote the parameters when we use them on the command line or within scripts. Learning this now can save us a lot of pain and heartache later, especially, when we start looking at loops.

First, the correct term that we should use for reading the value of variables is parameter expansion. To you and me this is reading a variable, but to bash this would be too simple. The assignment of a correct name, such as parameter expansion reduces any ambiguity to its meaning but adds complexity at the same time. In the following example, the first line of code assigns the value of fred to the name parameter. The second line of code uses...