Metasyntactic variable

A metasyntactic variable is name used in examples and understood to stand for whatever thing is under discussion, or any random member of a class of things under discussion. The word foo is the canonical example. To avoid confusion, hackers never (well, hardly ever) use ‘foo’ or other words like it as permanent names for anything. In filenames, a common convention is that any filename beginning with a metasyntactic-variable name is a scratch file that may be deleted at any time.

Metasyntactic variables are so called because (1) they are variables in the metalanguage used to talk about programs etc; (2) they are variables whose values are often variables (as in usages like “the value of f(foo,bar) is the sum of foo and bar”). However, it has been plausibly suggested that the real reason for the term “metasyntactic variable” is that it sounds good. To some extent, the list of one's preferred metasyntactic variables is a cultural signature. They occur both in series (used for related groups of variables or objects) and as singletons. Here are a few common signatures:

• foo, bar, baz, quux, quuux, quuuux...: A common recent mutation of this sequence inserts qux before quux.

• bazola, ztesch: Stanford (from mid-'70s on).

• foo, bar, bletch: Waterloo University. We are informed that the CS club at Waterloo formerly had a sign on its door reading “Ye Olde Foo Bar and Grill”; this led to an attempt to establish “grill” as the third metasyntactic variable, but it never caught on.

• foo, bar, fum: This series is reported to be common at XEROX PARC.

• flarp: Popular at Rutgers University and among GOSMACS hackers.

• zxc, spqr, wombat: Cambridge University (England).

• shme: Berkeley, GeoWorks, Ingres. Pronounced /shme/ with a short /e/.

• foo, bar, baz, bongo: Yale, late 1970s.

• spam, eggs: Python programmers.

• snork: Brown University, early 1970s.

• foo, bar, zot: Helsinki University of Technology, Finland.

• blarg, wibble: New Zealand.

• toto, titi, tata, tutu: France.

• pippo, pluto, paperino: Italy. Pippo /pee´po/ and Paperino /pa·per·ee'·no/ are the Italian names for Goofy and Donald Duck.

• aap, noot, mies: The Netherlands. These are the first words a child used to learn to spell on a Dutch spelling board.

• oogle, foogle, boogle; zork, gork, bork: These two series (which may be continued with other initial consonents) are reportedly common in England, and said to go back to Lewis Carroll.

Of all these, only foo and bar are universal (and baz nearly so). The compounds foobar and foobaz also enjoy very wide currency. Some jargon terms are also used as metasyntactic names; mumble, for example.

This article is based, in whole or in part, on an entry in the Jargon File.