live data

1. Data that is written to be interpreted and takes over program flow when triggered by some un-obvious operation, such as viewing it. One use of such hacks is to break security. For example, some smart terminals have commands that allow one to download strings to program keys; this can be used to write live data that, when listed to the terminal, infects it with a security-breaking virus that is triggered the next time a hapless user strikes that key. For another, there are some well-known bugs in vi that allow certain texts to send arbitrary commands back to the machine when they are simply viewed.

2. In C, data that includes pointers to functions (executable code).

3. An object, such as a trampoline, that is constructed on the fly by a program and intended to be executed as code.

4. Actual real-world data, as opposed to "test data". For example, "I think I have the record deletion module finished." "Have you tried it out on live data?" This usage usually carries the connotation that live data is more fragile and must not be corrupted, or bad things will happen. So a more appropriate response to the above claim might be: "Well, make sure it works perfectly before we throw live data at it." The implication here is that record deletion is something pretty significant, and a haywire record-deletion module running amok on live data would probably cause great harm.

[Jargon File]

Live Free Or Die!

1. The state motto of New Hampshire, which appears on that state's automobile licence plates.

2. A slogan associated with Unix in the romantic days when Unix aficionados saw themselves as a tiny, beleaguered underground tilting against the windmills of industry. The "free" referred specifically to freedom from the fascist design philosophies and crufty misfeatures common on commercial operating systems. Armando Stettner, one of the early Unix developers, used to give out fake licence plates bearing this motto under a large Unix, all in New Hampshire colours of green and white. These are now valued collector's items.



/li:v'lok/ When two or more processes continuously change their state in response to changes in the other process(es) without doing any useful work.

This is similar to deadlock in that no progress is made but differs in that neither process is blocked or waiting for anything.

A human example of livelock would be two people who meet face-to-face in a corridor and each moves aside to let the other pass, but they end up swaying from side to side without making any progress because they always move the same way at the same time.

[Jargon File]

Last updated: 1998-07-05




/li:v'weir/ 1. A less common synonym for wetware

2. (Cambridge) Vermin. "Waiter, there's some liveware in my salad."

[Jargon File]

Last updated: 1995-10-30

Nearby terms:

little-endianLittle Smalltalklive dataLive Free Or Die!livelock

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