Variables can represent lists of file names, options to pass to compilers, programs to run, directories to look in for source files, directories to write output in, or anything else you can imagine. Variable names are case-sensitive. A few variables have names that are a single punctuation character or just a few characters. These are the automatic variables , and they have particular specialized uses. See section Automatic Variables .
Variables come in two flavors.
Advanced features for referencing a variable. All the ways variables get their values. Variable values can come from the environment. Go to the first , previous , next , last section, table of contents .