CHAPTER 9 Shell Programming
Bourne shell C shell
param=value set param = value
where value is any valid string, and can be enclosed within quotations, either single ('value) or double ("value"), to allow spaces within the string value. When enclosed with backquotes ('value') the string is first evaluated by the shell and the result is substituted. This is often used to run a command, substituting the command output for value, e.g.:
$ day='date +%a'
$ echo $day
Wed
After the parameter values has been assigned the current value of the parameter is accessed using the $param, or ${param}, notation.