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UNIXIntroductionWhatisUNIX?UNIXisanoperatingsystemwhichwasfirstdevelopedinthe1960s,andhasbeenunderconstantdevelopmenteversince.Byoperatingsystem,wemeanthesuiteofprogramswhichmakethecomputerwork.Itisastable,multi-user,multi-taskingsystemforservers,desktopsandlaptops.UNIXsystemsalsohaveagraphicaluserinterface(GUI)similartoMicrosoftWindowswhichprovidesaneasytouseenvironment.However,knowledgeofUNIXisrequiredforoperationswhicharen'tcoveredbyagraphicalprogram,orforwhenthereisnowindowsinterfaceavailable,forexample,inatelnetsession.TypesofUNIXTherearemanydifferentversionsofUNIX,althoughtheysharecommonsimilarities.ThemostpopularvarietiesofUNIXareSunSolaris,GNU/Linux,andMacOSX.HereintheSchool,weuseSolarisonourserversandworkstations,andFedoraLinuxontheserversanddesktopPCs.TheUNIXoperatingsystemTheUNIXoperatingsystemismadeupofthreeparts;thekernel,theshellandtheprograms.ThekernelThekernelofUNIXisthehuboftheoperatingsystem:itallocatestimeandmemorytoprogramsandhandlesthefilestoreandcommunicationsinresponsetosystemcalls.Asanillustrationofthewaythattheshellandthekernelworktogether,supposeausertypesrmmyfile(whichhastheeffectofremovingthefilemyfile).Theshellsearchesthefilestoreforthefilecontainingtheprogramrm,andthenrequeststhekernel,throughsystemcalls,toexecutetheprogramrmonmyfile.Whentheprocessrmmyfilehasfinishedrunning,theshellthenreturnstheUNIXprompt%totheuser,indicatingthatitiswaitingforfurthercommands.TheshellTheshellactsasaninterfacebetweentheuserandthekernel.Whenauserlogsin,theloginprogramcheckstheusernameandpassword,andthenstartsanotherprogramcalledtheshell.Theshellisacommandlineinterpreter(CLI).Itinterpretsthecommandstheusertypesinandarrangesforthemtobecarriedout.Thecommandsarethemselvesprograms:whentheyterminate,theshellgivestheuseranotherprompt(%onoursystems).Theadeptusercancustomisehis/herownshell,anduserscanusedifferentshellsonthesamemachine.Staffandstudentsintheschoolhavethetcshshellbydefault.Thetcshshellhascertainfeaturestohelptheuserinputtingcommands.F
