DAEMON
\dˈiːmən], \dˈiːmən], \d_ˈiː_m_ə_n]\
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By Princeton University
By DataStellar Co., Ltd
By James Champlin Fernald
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/day'mn/ or /dee'mn/ (From the mythologicalmeaning, later rationalised as the acronym "Disk And ExecutionMONitor") A program that is not invoked explicitly, but liesdormant waiting for some condition(s) to occur. The idea isthat the perpetrator of the condition need not be aware that adaemon is lurking (though often a program will commit anaction only because it knows that it will implicitly invoke adaemon).For example, under ITS writing a file on the LPT spooler'sdirectory would invoke the spooling daemon, which would thenprint the file. The advantage is that programs wanting filesprinted need neither compete for access to, nor understand anyidiosyncrasies of, the LPT. They simply enter theirimplicit requests and let the daemon decide what to do withthem. Daemons are usually spawned automatically by thesystem, and may either live forever or be regenerated atintervals.Unix systems run many daemons, chiefly to handle requestsfor services from other hosts on a network. Most of theseare now started as required by a single real daemon, inetd,rather than running continuously. Examples are cron (localtimed command execution), rshd (remote command execution),rlogind and telnetd (remote login), ftpd, nfsd (filetransfer), lpd (printing).Daemon and demon are often used interchangeably, but seem tohave distinct connotations (see demon). The term "daemon"was introduced to computing by CTSS people (who pronouncedit /dee'mon/) and used it to refer to what ITS called adragon.
By Denis Howe
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