In programming, a metasyntactic (which derives from meta and syntax ) variable is a variable (a changeable value) that is used to temporarily represent a function . Examples of metasyntactic variables include (but are by no means limited to) ack, bar , baz, blarg, wibble, foo , fum, and qux. Metasyntactic variables are sometimes used in developing a conceptual version of a program or examples of programming code written for illustrative purposes.
Any filename beginning with a metasyntactic variable denotes a scratch file. This means the file can be deleted at any time without affecting the program.