General C Programming Examples.docx

General C Programming Examples.docx

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GeneralCProgrammingExamples

GeneralCProgrammingExamples

TableofContents

Introduction

1.ProgramFormat

CProgramFormat

User-DefinedFunctionsinC

LoadRunnerScriptsandC

2.DataTypes

IntegerType

FloatType

CharType

FormatControl

Exercise2.1

3.ControlFlow

BooleanOperators

IfStatements

SwitchStatement

Exercise3.1

ForLoops

While

DoWhile

breakandcontinue

Exercise3.2

The?

operator

4.ArraysandStrings

Arrays

Strings

Exercise4.1

StringManipulation

Multi-DimensionalArrays

5.FileProcessing

FileDeclaration

FileOpening

FileReading

Exercise5.1

FileWriting

Exercise5.2

6.Functions

User-definedFunctions

Exercise6.1

IncludeFiles

Exercise6.2

7.MiscellaneousFunctions

System

RandomNumbers

Solutions

Exercise2.1

Exercise3.1

Exercise3.2

Exercise4.1

Exercise5.1

Exercise5.2

Exercise6.1

Introduction

MyinitialplanwastocreateaCreferencemanualfortheMercuryTestTeam.ThisisbecauseLoadRunnerscriptsconsistofcallstoLoadRunnerfunctions,whichareessentiallyCfunctionlibraries.SinceCformsthebasisforLoadRunnerscripts,mostofthefunctionsinCaresupportedinLoadRunner.ExpertiseinCwillhelpyoucustomizeandimprovethescriptsgreatly.SowethoughtthataCreferencemanualwouldbeveryuseful.

ThoughLoadRunnerisbasedonC,thereareafewvariationsandexceptionstotheCfunctionsthataresupportedinLoadRunner.Moreover,IdidnotwanttoaddtheoverheadofowningaCcompilertogothroughtheexercisesinthismanual.SoIthoughtI’dcreateamanualthatwouldworkwithVirtualUserGenerator（Vugen）.Iamhopingthatbythetimeyougettothismanual,youarealreadyfamiliarwiththecomponentsofLoadRunner.

AllexercisesinthismanualcanbecompiledandruninVugen.AsIdiscusseachtopicinC,I’llalsodiscusshowitdiffersinLoadRunnerandthecontextinwhichthisfunctionmightbeuseful.ThiswillbothfamiliarizeyouwithCfromaLoadRunnerperspective,andmakeyoucomfortablewithusingcustomcodinginLoadRunner.

IfyouarealreadycomfortablewithC,youmightbeabletoskimthroughthismanualinnotime.PleasenotethatthepurposeofthismanualisnottomakeaCexpertoutofyou;mostoftheconceptsandexercisesinhereareveryelementary.ThiswilljustbeaquickC/LoadRunnerreference.

Hopeyoufindthisworkuseful.

1.ProgramFormat

Inthissection,wewilldiscusstheCprogramformatandhowitrelatestoLoadRunner.

CProgramFormat

Everyprogramminglanguagehasasetofrules,calledsyntaxofthelanguage,thatgovernhowlegalprogramsareconstructed.AprograminCcanbemadeupofmanycomponents,sometimesspreadoverseveralfiles.

WewilltakealookataverysimplebutpopularCprogram:

#include

main（）

{

/*Thisprogramprints

“HelloWorld!

”*/

printf（“HelloWorld!

”）;

}

Thefirstline,#include,isasignalthatsomeinformationshouldbeaddedtotheprogramfromanexternalfile,eitherasystemfileasinthiscase（isastandardinputandoutputlibrary）,orauserdefinedfile.

Thebodyoftheprogramiscontainedinmain（）,encapsulatedby{}.

CommentsinCaresurroundedby/*and*/.TheCcompilerignoresalltextwithinthecomments.

Theonlystatementintheprogram,printf（“HelloWorld!

”）instructstheprogramtoprintthe“HelloWorld!

”tothestandardoutput.Now,thefunctionprintfisdefinedinstdio.h,andthatisthereasonweincludedstdio.habovethemain.

User-DefinedFunctionsinC

WeareviolatingeveryruleintheartofC-instructionbyintroducinguser-definedfunctionssoearlyinthegame.Butitisveryimportanttounderstanduser-definedfunctionstointroducehowLoadRunnerscriptstieintoCprogramming.Atthispoint,wewillintroduceuser-definedfunctionsataconceptuallevel,andgetintothedetailsinalatersection.

IntheHelloWorldprogram,weusedthefunctionprintf,whichprintsthegivenmessagetothestandardoutput.Theprintffunctionisastandardbuilt-infunctioninC.Sothecompilerunderstandstheactionrequestedbytheuseofthatfunction.Butitisoftennecessaryinprogrammingtocreateyourownfunctionstoaccomplishcertaintasks.Thesefunctionsarecalleduser-definedfunctions.

Forexample,letssayyouhavetoprintthefollowingtextanumberoftimesinyourprogram:

$$$$$$$$$$$

HelloWorld!

$$$$$$$$$$$

Thiscanbeaccomplishedbycreatingafunctionthatwillprinttheabovetextandcallingthefunctionanumberoftimesasrequired.

Thisiswhatyourprogramwilllooklike:

#include

my_function（）

{

/*Textgeneratingcode*/

printf（“$$$$$$$$$$$\n”）;

printf（“HelloWorld!

\n”）;

printf（“$$$$$$$$$$$\n\n”）;

}

main（）

{

my_function（）;/*call1*/

printf（“Thisprogramdemonstratesuser-definedfunctions.\n\n”）;

my_function（）;/*call2*/

}

Intheaboveprogram,wedefinedafunctionnamedmy_function,whichwascalledtwiceinthemain（call1andcall2）.Thefollowingwillbetheoutputoftheaboveprogram.Youcanseethateverytimethefunctionmy_functionwascalled,the3-linetextoutputwasgenerated.

$$$$$$$$$$$

HelloWorld!

$$$$$$$$$$$

Thisprogramdemonstratesuser-definedfunctions

$$$$$$$$$$$

HelloWorld!

$$$$$$$$$$$

Bycreatingafunctiontogeneratethetextoutput,weavoidedtheneedtowritethetext-generatingcodeoverandoverinthemainprogram.Wecansimplycallthefunctionasmanytimesasweneed.

Theaboveisatrivialexampleofauser-definedfunctionwithasinglepurpose.Multi-purposeandreusablefunctionscanbecreatedbyuseofparameters.Thiswillbediscussedinalatersection.

NowthatwehaveanideaofwhataCfunctionis,letuslookathowLoadRunnerscriptsrelatetoC.

LoadRunnerScriptsandC

InVugen,youmayhavenoticedthataLoadRunnerscriptconsistsofinit,actionsandendsections.InLoadRunner6.0andabove,youcanhavemultipleactionssectionsasshowninfigure1.1.

Figure1.1:

Vugen

LetslookattheabovescriptfromaCprogrammingpointofview.WhenyourecordascriptintodifferentsectionsofVugen,eachsectionwillberecordedlikearegularCfunction.Intheabovefigure,vuser_init,Action1,Action2andvuser_endwillbeour4functions.Iftheabovescriptissettorun3iterations,thisishowanequivalentCprogramwouldlooklike:

main（）

{

/*callinginitsection*/

vuser_init（）;

/*callingactionssectioniteration1*/

Action1（）;

Action2（）;

/*callingactionssectioniteration2*/

Action1（）;

Action2（）;

/*callingactionssectioniteration3*/

Action1（）;

Action2（）;

vuser_end（）;

}

whereeachfunctionisdefinedintheVugenscript.ThereisnomaininLoadRunner.Itisautomaticallytakencareofbehindthescenes.Differentsectionsofthescriptsaretheonlyvisiblepartsoftheprogram.

Whatgoesonbehindthescenesisalotmoreugly,buttheaboveisasimplisticrepresentationoftheidea.Thevuserwillexecuteallactionscorrespondingtothatsectionwhenafunctioniscalled.Itisimportanttounderstandthateachsectioninthescriptistreatedlikeauser-definedfunction.

Example:

Intheabovescript,letssayeachsectionprintsamessageidentifyingitself.ThefollowingwillbetheoutputintheexecutionlogofVugen:

VirtualUserScriptstarted

vuser_init.c（3）:

Youareinvuser_init

RunningVuser...

Startingiteration1.

Action1.c（3）:

YouareinActions1

Action2.c（3）:

YouareinActions2

Endingiteration1.

Startingiteration2.

Action1.c（3）:

YouareinActions1

Action2.c（3）:

YouareinActions2

Endingiteration2.

Startingiteration3.

Action1.c（3）:

YouareinActions1

Action2.c（3）:

YouareinActions2

Endingiteration3.

EndingVuser...

vuser_end.c（3）:

Youareinvuser_end

VuserTerminated.

Inarealscript,eachofthesefunctionsmightbeexercisingtheapplicationundertest（AUT）,ratherthanjustprintingprettylittlemessages.

TheideabehindthischapterwasjusttofamiliarizeyouwiththeLoadRunnerprogramstructureandcompareittoC.WewillfocusondifferentelementsofCintheupcomingsections.

2.DataTypes

Ithink“HelloWorld”istheonlyrespectedprogramintheworldthatdoesnotcontainvariables.Ifyouwantyourprogramtodoanythingremotelyinteresting,youwillhavetousevariables.Inthischapter,wewillseethedifferentdatatypesinwhichavariablecanbedeclared.

Forexample,avariablecalledcountcanbedeclaredasanintegertype.

intcount=0;

Nowthevariablecountcanassumeanyintegervalueduringtheprogramexecution.Therearelimitationsonthesizeandprecisionofeachdatatype,whichwewilldiscussshortly.AllvariablesinCmustbedeclaredbeforetheycanbeused.

IntegerType

Asthenamesuggests,thistypeisusedtodeclarevariablestocontainintegervalues.Typically,shortintegersrangeinvaluesbetween–32,768to32767（Theprecisiondependsonthenumberofbitsused）.Longinteger,orjustdeclaredasintinLoadRunner,rangesinvaluesfrom–2147483648to2147483648（Noshortageofvaluesthere!

）.Unlessyouareusingawholelotofvariables,whichisnotthecasetypicallyinLoadRunner,youdon’thavetoworryaboutmemoryconsiderations.Butnotethatashortinttakeslesserspaceinmemorycomparedtoaregularinteger.

FloatType

Floattypeisusedfornon-integralvaluesliketheonebelow:

floatx=2.564;

Floatrangesinvaluesfrom10-38to1038.Forgreaterrange,youcanusedouble,whichrangesinvaluesfrom10-308to10308.Wewillrarelyneedthisdatat