Nachos Project 2B: Multiprogramming - Operating System | CMSC 321 | Study Guides, Projects, Research Operating Systems

CMSC321—OperatingSystems

NachosProject2(b):Multiprogrammingi

DueDate:11:59pmWednesday01April2009

ThesespecificationsdescribethesecondsubprojecttocompletephasetwoofNachos.Continuingwith

thespecificationsfromNachosProject2(a),hereistheassignment:

1. TheExec()systemcalldoesnotprovideanywayfortheuserprogramtopassparametersor

argumentstothenewlycreatedaddressspace.UNIXdoesallowthis,forinstance,topassin

commandlineargumentstothenewaddressspace.Implementthisfeature.Theprototypeforthe

newimprovedExecis:

SpaceIdExec(char*name,char*args[]);

Here,argsisavectorofpointerstothestringswhicharetheargumentspassedintothechild

process.ANULLpointerterminatesthevector.Byconvention,args[0]shouldbesettobethename

oftheprograminvoked(i.e.,usuallythelastcomponentintheabsolutefilenameoftheExec‐ed

binary).WhentheExec‐eduserprocessbeginsexecution,themainfunctionisessentiallycalledas

main(intargc,char*argv[])

Theintegerargcistheargumentcount.Sinceargv[0]isalwayssetbyconvention,argcshouldbeat

least1.Thelastprogramargumentwillbedenotedbyargv[argc‐1].

2. Writeashellandsomeutilityprograms.Ashellreadsacommandfromtheuserviatheconsole,

thenrunsthecommandbyinvokingthekernelsystemcallExec().TheUNIXprogrambashisan

exampleofashell.Thereisalreadyasimpleshellinthetestdirectory.Enhanceittodosome

interestingthings.Alsoadapttheshelltoinvokeprogramswithcommandlinearguments(usingthe

Exec()youwroteabove).Testyourshellandsystemcallhandlingbywritingacoupleofutility

programs,suchasUNIXcat,cp,etc.





iFromtheoriginalNachosAssignment#2byTomAnderson;modifiedbyPhilKearnsandlaterJoelHollingsworth,

BarryLawsonandLewisBarnett

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CMSC 321 — Operating Systems