= M =
magic cookie n.
[Unix; common] 1. Something passed
between routines or programs that enables the receiver to perform
some operation; a capability ticket or opaque identifier.
Especially used of small data objects that contain data encoded in
a strange or intrinsically machine-dependent way. E.g., on
non-Unix OSes with a non-byte-stream model of files, the result of
ftell(3) may be a magic cookie rather than a byte offset; it
can be passed to fseek(3), but not operated on in any
meaningful way. The phrase `it hands you a magic cookie' means
it returns a result whose contents are not defined but which can be
passed back to the same or some other program later. 2. An in-band
code for changing graphic rendition (e.g., inverse video or
underlining) or performing other control functions (see also
cookie). Some older terminals would leave a blank on the
screen corresponding to mode-change magic cookies; this was also
called a glitch (or occasionally a `turd'; compare mouse droppings). See also cookie.
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.