Demon
See also: Demon
In the field of the Data-processing , the term demon (or demon in English) indicates a type of program. The term was created by the inventors of Unix to refer to a process which is carried out in background rather than under the direct control of a user. It comes from the English word demon , transcription of the Greek δαιμων. The acronym Disk And Execution Monitor (monitor of disc and execution) was invented to justify the term demon after it became popular.
The demons are often started during the loading of the operating system, and are in general used to answer requests of the network, the activity of the material or other programs by carrying out certain tasks. On Microsoft Windows, these functions are carried out by programs called “ services ”, even if the term “ démon ” seems more and more used.
On a strictly technical side, a demon on a Unix-compatible system Unix or can be any process which has the process number 1 like relative ( Init ). Any process whose relative dies without awaiting the statute of his process child is adopted by init. A common way to launch a demon is thus “ fourcher ” ( Fork ) one or twice and to make stop the relative when the child begins his normal operations. This way of doing is some times summarized by the sentence fork off and die (“ fourcher and mourir ”). In the common use, a demon can be any process which functions in background, it does not matter that he is or not a child of init.
The demons can also be used to configure the material (like devfsd on the systems GNU/Linux), to carry out repetitive tasks (like Cron d) or to make a variety of other tasks.
Anecdote
The waiters emails, which must turn permanently, are demons: look at the emails which to you are returned if the recipient is non-existent, most of the time the shipper is " mailer-demon@fai.fr".
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