Mastering Windows PowerShell Scriptingsentinel/roar/Mastering PowerShell-Packt...Table of Contents Mastering Windows PowerShell Scripting Credits Foreword About the Author About the

MasteringWindowsPowerShellScripting

TableofContents


Credits

Foreword

AbouttheAuthor

AbouttheReviewers

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Whysubscribe?

FreeaccessforPacktaccountholders

InstantupdatesonnewPacktbooks

Preface

Whatthisbookcovers

Whatyouneedforthisbook

Whothisbookisfor

Conventions

Readerfeedback

Customersupport

Downloadingtheexamplecode

Errata

Piracy

Questions

1.Variables,Arrays,andHashes

Variables

Objectsstoredinvariables

Arrays

Single-dimensionarrays

Jaggedarrays

Updatingarrayvalues

Hashes

Decidingthebestcontainerforyourscripts

Summary

2.DataParsingandManipulation

Stringmanipulation

Replacingandsplittingstrings

Countingandtrimmingstrings

TheTrimmethod

TheSubstringmethod

Thestringtrueandfalsemethods

Numbermanipulationandparsing

Formattingnumbers

Formattingbytes

Dateandtimemanipulation

Forcingdatatypes

Pipingvariables

Summary

3.ComparisonOperators

Comparisonoperatorbasics

Equalandnotequalcomparison

Greaterthanandlessthancomparison

Contains,like,andmatchoperators

And/ORcomparisonoperators

Bestpracticesforcomparisonoperators

Summary

4.Functions,Switches,andLoopsStructures

Functions

Loopingstructures

Switches

Combiningtheuseoffunctions,switches,andloops

Bestpracticesforfunctions,switches,andloops

Bestpracticesforfunctions

Bestpracticesforloopingstructuresandswitches

Summary

5.RegularExpressions

Gettingstartedwithregularexpressions

Regularexpressiongroupingconstructsandranges

Regularexpressionquantifiers

Regularexpressionanchors

Regularexpressionsexamples

Summary

6.ErrorandExceptionHandlingandTestingCode

Errorandexceptionhandling–parameters

Errorandexceptionhandling–Try/Catch

Errorandexceptionhandling–Try/Catchwithparameters

Errorandexceptionhandling–legacyexceptionhandling

Methodologiesfortestingcode

Testingthe–WhatIfargument

Testingthefrequency

Hittestingcontainers

Don’ttestinproduction

Summary

7.Session-basedRemoteManagement

UtilizingCIMsessions

Creatingasession

Creatingasessionwithsessionoptions

Usingsessionsforremotemanagement

Removingsessions

Summary

8.ManagingFiles,Folders,andRegistryItems

Registryprovider

Creatingfiles,folders,andregistryitemswithPowerShell

Addingnamedvaluestoregistrykeys

Verifyingfiles,folders,andregistryitems

Copyingandmovingfilesandfolders

Renamingfiles,folders,registrykeys,andnamedvalues

Deletingfiles,folders,registrykeys,andnamedvalues

Summary

9.File,Folder,andRegistryAttributes,ACLs,andProperties

Retrievingattributesandproperties

Viewingfileandfolderextendedattributes

Settingthemodeandextendedfileandfolderattributes

Managingfile,folder,andregistrypermissions

Copyingaccesscontrollists

AddingandremovingACLrules

Summary

10.WindowsManagementInstrumentation

WMIstructure

UsingWMIobjects

SearchingforWMIclasses

Creating,modifying,andremovingWMIpropertyinstances

Creatingpropertyinstances

Modifyingpropertyinstances

Removingpropertyinstances

InvokingWMIclassmethods

Summary

11.XMLManipulation

XMLfilestructure

ReadingXMLfiles

AddingXMLcontent

ModifyingXMLcontent

RemovingXMLcontent

Summary

12.ManagingMicrosoftSystemswithPowerShell

Managinglocalusersandgroups

Managinglocalusers

Managinglocalgroups

Queryingforlocalusersandgroups

ManagingWindowsservices

ManagingWindowsprocesses

InstallingWindowsfeaturesandroles

Summary

13.AutomationoftheEnvironment

Invokingprogramsforautomation

Usingdesiredstateconfiguration

Authoringphase

Stagingandremediationphase

Detectingandrestoringdriftingconfigurations

Summary

14.ScriptCreationBestPracticesandConclusion

Bestpracticesforscriptmanagement

#commentingheaders

Commentingcode

Bestpracticesforscriptcreation

Scriptstructure

Otherimportantbestpracticesforscriptcreation

Controllingsourcefiles

Bestpracticesforsoftwareautomation

Summary

MasteringWindowsPowerShellScripting–conclusion

Stayingconnectedwiththeauthor

Index

MasteringWindowsPowerShellScriptingCopyright©2015PacktPublishing

Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.

Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishing,anditsdealersanddistributorswillbeheldliableforanydamagescausedorallegedtobecauseddirectlyorindirectlybythisbook.

PacktPublishinghasendeavoredtoprovidetrademarkinformationaboutallofthecompaniesandproductsmentionedinthisbookbytheappropriateuseofcapitals.However,PacktPublishingcannotguaranteetheaccuracyofthisinformation.

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CreditsAuthor

BrentonJ.W.Blawat

Reviewers

TimAmico

ChristopheCRÉMON

TomasRestrepo

AcquisitionEditor

MeetaRajani

ContentDevelopmentEditor

RohitSingh

TechnicalEditor

TanviBhatt

CopyEditors

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ProjectCoordinator

MaryAlex

Proofreaders

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SafisEditing

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Indexer

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ProductionCoordinator

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CoverWork

AlwinRoy

ForewordWeallappreciatealittlesimplicitywhenitentersourbusy,complicatedlives.Technologyisnodifferent.Infact,thatiswhatweexpectfromtechnology—itshouldsimplifyourlives.Butitdoesn’talwaysworkthatway.

Sometimestechnologycanintroducevexingproblemswedon’tanticipate.

WitheveryversionofMicrosoftDOSandthenWindows,Microsoftincludedseparatecommand-lineinterfaceshells.Theshellcouldautomatesometasks,butnotallofthem.Sometaskshadtobeaccomplishedmanually,whichisantithetical—nearlyheretical—toourunderstandingoftechnology’srole.

Whatshouldhavebeensimple,automatedtasksbecameslow,frustrating,andmanualchores.Thatconundrumdidn’tgounnoticed.

Microsoftprovidedmuch-neededsimplicitywhenitintroducedPowerShellin2006.Taskautomationandconfigurationmanagementeliminatedagreatdealoftime-consumingmanualwork.Inshort,PowerShellwasagamechanger.

PowerShellhassolvedmanyofthecommand-lineandscriptingissuesthatcomplicatedourwork.Itintroducedsimplicity.Ithelpedorganizationsbecomemoreagile,moreproductive,andsavemoney.PowerShellisapowerfultool,andithasdemonstrateditspracticalvaluemanytimes.

Despiteitsutility,though,PowerShellremainsaconfusingtooltomanyITadministrators,andtheneedforgreaterclarityremains.

ItisthroughthislensthatMr.BrentonBlawatprovidesaninsightfulnewanalysisofPowerShell—avaluableguidebookforthosewhostruggletounderstandPowerShell.OthershaveofferednarrativesthatattempttoexplainPowerShell,buttheyrarelyprovidetheroadmap,background,orcontextthatadministratorsneedtogetfromPointAtoPointB.

So,thisistherighttimeforacomprehensivenewanalysis.

Ingeneralterms,Mr.Blawat’sbookwillhelpthosewhostruggletomanagetheircomputeenvironments.ItincludesimportantguidanceonprogramminginPowerShell,startingwithbasicconceptsandthenintroducingadvancedconfigurations.

Mr.Blawatdeconstructsanddemystifiesthisprogramminglanguage,sharinghisintimateknowledgeinaformatthatdemonstratestheclarityofthoughtandprosethatadifficultsubjectrequires.Manyauthorshaveattemptedthisclimb,butonlyMr.Blawathasreachedthesummit.Hisexaminationprovidesrelevantinformationforadministratorswhoworkwith—andsometimesstrugglewith—PowerShellonadailybasis.

AsMr.Blawatexplainsinthefollowingpages,therapidadoptionofcloud-basedtechnologiesparalleledthenever-endingneedforadditionalcomputingpowerindatacenters.Thiscreatedtheneedtoefficientlybuildandexpandsystemswithextremeprecision.Inadditiontoprovisioningthebasesystems,therewasaneedtodynamically

customizethesenewsystemstoworkinunisonwithcurrentrunningenvironments.

Thisdrovetheneedforthenextgenerationsystemautomationlanguagesthatwouldprovidefullconfigurationforsystemsonthefly.Notonlydotheseautomationlanguagesgreatlyreducetimetouse,buttheyalsoensurethatnomistakesaremadeduringtheconfigurationprocess.Allsystemsarecreatedequally.

PowerShellisa.NET-basednextgenerationautomationlanguagethatprovidesbothsystemsprovisioningandmanagementfunctionalityforWindows-basedsystems.Leveragingcommand-linelikeinteractions,PowerShellcanbecompiledintoscriptsthatcansystematicallyexecutetasksonasystem.Notlimitedtocreatingnewsystems,engineersareleveragingPowerShelltoautomatemundanetaskssothattheycanfocusonotherpressingactivitiesintheirenvironments.

MicrosofthasfullyembracedPowerShellinitsfullsoftwareportfoliotoofferfullintegrationwithitsproducts.NotonlycanyoudynamicallyinstalltheMicrosoftsoftware,butyoucanalsofullymanagetheentireMicrosoftsoftwareenvironmentusingPowerShell.PowerShellhasalsobeenembracedbythird-partymanufacturersthroughtheintegrationofPowerShellmodules.Thesemodulesprovidefullmanagementcapabilitiesforproductssuchasnetworkdevices,storagesubsystems,virtualizationguestsandhosts,securityappliances,andotherthird-partyapplications.

Likemanyorganizations,CDWhasbenefittedgreatlyfromPowerShell,sothisbookhitsveryclosetohomeforme.WeusePowerShellscriptstomanagecustomerenvironmentsinmanagedservicesandtheinstallationofmanagementtools.

WeuseMicrosoftOrchestratortoprovideback-endlogicforsimpleuserinterfacesforhelpdeskactivities,likeuser-drivenpasswordresetsanduser-drivensoftwareinstallations.WealsorelyonMicrosoftOrchestratortoautomaticallytroubleshootandremediatesystems.

CDW’scustomersalsobenefitfromPowerShellinmyriadways.WeassistawidevarietyofFortune500clientstodevelopPowerShellautomationscriptstobuildnewsystemsandmanagetheirenvironments,includinghealthcheckscripts,systemsdiscovery,andadvancedregulatorysecurityanalysis.

Clearly,PowerShell’sincredibleutilityhasmadeitinvaluabletoCDW,ourcustomers,andcountlessorganizationsacrosstheglobe.Butunderstandingallofitsmanyfacetsrepresentsadauntingtask.OrganizationsareunabletoleveragePowerShelliftheydon’tfullyunderstanditspotential.

That’swhereMr.Blawatexcels.

Mr.Blawat’scomprehensivenewworkwillserveasareferencetoolforengineerswhoworkwithWindowsbytakingthemysteryoutofcommontasksthataren’teasilyunderstoodandaren’talwaysintuitive.DiligentreaderswillnodoubtfindmanymorereasonstogiveMr.Blawat’sthoroughnarrativeaprominentplaceontheirbookshelves.

AsMr.Blawat’scoworker,Ialsofeelproudthatheissharinghisknowledgewiththeworld—notonlysootherscanbenefitfromhisexperience,butsotheycanseewhatthose

ofuswhoworkwithhimatCDWwitnessonadailybasis.

PowerShellhasproventobeanincrediblyusefultoolforITadministratorssinceitburstontothescene.NowthereisabookaboutPowerShellthatwillproveequallyuseful.

JonStevens

ChiefInformationOfficer

CDW

AbouttheAuthorBrentonJ.W.Blawatisanentrepreneur,strategictechnicaladvisor,author,andseniorconsultant,whohasapassionfortheprocurementoftechnologyinprofit-basedorganizations.Heisbusiness-centricandtechnology-minded.Brentonhasmanyyearsofexperienceinbridgingthegapbetweentechnicalstaffanddecision-makersinseveralorganizations.Hetakesprideinhisabilitytoeffectivelycommunicatewithadiverseaudienceandprovidestrategicdirectionforlargeandsmallorganizationsalike.

In2013,Brentonauthoredhisfirstbook,PowerShell3.0WMIStarter,PacktPublishing.ThisbookwasdesignedtobeastarterforthoseinterestedinmanipulatingWindowsManagementInstrumentationthroughtheuseofPowerShell3.0.Thisbookisavailableinallpopularbookstores,includingPacktPublishing’swebsite,http://bit.ly/18pcpGK.

BrentoncurrentlyworksatCDWasaseniorconsultingengineerinstrategicsolutionsandservices.CDWisaleadingmultibrandtechnologysolutionsproviderinthefieldsofbusiness,government,education,andhealthcare.AFortune500company,itwasfoundedin1984andemploysapproximately7,200coworkers.In2014,thecompanygeneratednetsalesofmorethan$12.0billion.FormoreinformationaboutCDW,youcanvisitwww.CDW.com.

Iwouldliketothanktheforewordcoordinationteam,MaryViola,ScottThomas,JimmyThomson,BrandonKing,SondraRagusin,MeredithBraselman,andBillGlanz.Iwouldliketodedicatethisbooktomybeautifulnieces,CaliettandEvie.

http://bit.ly/18pcpGKhttp://www.CDW.com

AbouttheReviewersTimAmicoisaconsultingengineeratCDW,whospecializesinConfigurationManagerandOperatingSystemDeployment.HestartedhiscareerinITbackin1998,whenheworkedasaconfigurationtechforCompuCom,learningaboutwhatisrequiredtobecomeanITprofessional.Sincethen,hehasclimbedtheladderfromhardwarefieldsupportandsoftwaredeploymentsupporttohiscurrentrole(forthelast10years)asanITconsultant,designingandimplementingendpointandmobilitymanagementsolutions.ApartfromConfigurationManagerandOSD,TimalsohasexperienceinPowerShell,BitLockerdriveencryptiondeployments,IntelvProprovisioningandusecasedesign,ActiveDirectory(bothinAzureandWindowsServer),SQLdesignandreporting,PKIdesign,andMicrosoftIntune.

ChristopheCRÉMONisaSharePointinfrastructurearchitect,with10yearsofexperienceininformationtechnology,especiallyMicrosoft.HehasbeenusingPowerShellsince2008,andhaspublishedusefulscriptsandmodulesforITAdministratorsatpowershell.codeplex.com.Hehasapersonalwebsiteatwww.christophecremon.com.

TomasRestrepohasbeenwritingsoftwareforover10years,startingwithC/C++andeventuallymovingtothe.NETplatform.Hecurrentlyspendsmostofhistimehelpingotherdeveloperssolvecomplexproblemsandtroubleshootingapplicationperformanceandscalabilityissues.

http://powershell.codeplex.comhttp://www.christophecremon.com

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PrefacePowerShellisanetworkscriptinglanguagethatprovidesasetoftoolstoadministerMicrosoftproducts.WhilePowerShellisbasedoncommand-lineinteractions,itismuchmorepowerfulthanwhatthestandardcommandlineoffers.Ithasbuilt-insectionsofcodecalledcmdlets.Theysimplifyfunctionsthatyoumayneedtoperformonasystem.Usingcmdletsgreatlyreducesthenumberoflinesofcodethatarerequiredtoperformactions,comparedtootherscriptinglanguages,suchasVBScript.

PowerShellisbasedontheverb-nounnamingconvention,whichallowsscripterstodeclareanactionfollowedbyanobjecttoconfigure.Forexample,theget-servicecmdleteasilydesignatesthatyouaregettingaWindowsservice.ThisliteralnamingconventionhelpsreadersquicklylearnhowtoprograminPowerShell,astheactionsareeasilyremembered.

CommunitysupportforPowerShellhasgrownastronomically.NotonlyhavelargecompaniesadoptedPowerShellintheirenvironments,butuniversitiesarealsoregularlyteachingPowerShellcoursestotheirstudents.PowerShell’sfeaturesetkeepsgrowingwitheveryreleaseoftheproduct.Itisconceivableinthenearfuturethatyouwillbeabletofullyautomatetheconfigurationofeverycomponentinadatacenter.Thiswillremovetheneedsofmultipleengineeringspecialiststoprovisionnetworking,storage,firewalls,operatingsystemsbuilds,andhigh-availabilityconfigurations.ItwillallbedoneviaPowerShellscriptingandthesystemswillbeabletobeconfiguredusingasingularnetworklanguage.

ThisbookprovidesastrongfoundationforlearningPowerShellusingreal-worldscenarios.Youwillnotonlybeabletoquicklylearnhowtoprograminthislanguage,butalsobeabletoproducescriptsthatyoucanuseinyourexistingenvironments.Thisbookwillalsobeagreatreferencebookforyoutolookbackonandrevisitasyouarecoding.Itwillprovidethepropersyntaxandshowyousuccessfulwaystoimplementyourcode.Whenyouaredonewithreadingthisbook,youwillbewellonyourwayto“masteringPowerShell”!

WhatthisbookcoversChapter1,Variables,Arrays,andHashes,exploresthedifferentdataandobjectcontainersthatyoucanuseinPowerShell.Thesecontainersincludevariables,arrays,andhashes.Thischapterprovidesexamplesonhowtousethesecontainerstostoreobjects.

Chapter2,DataParsingandManipulation,divesintothedifferentdatatypesandhowtomanipulatetheminyourscripts.Thesedatatypeexamplesincludestrings,integers,dates,XML,andmanymore.

Chapter3,ComparisonOperators,evaluatesmultiplecomparisonoperatorsanddisplayshowtouseeachofthesecomparisonoperators.Thischapteralsodisplayshowtoleverageimpliedtrueandfalsecomparisonoperators.

Chapter4,Functions,Switches,andLoopsStructures,displaystheuseofdifferentdatastructurestoperformrepeatableactions.Itprovidesexamplesonhowtoparselargearraysofdatathroughloopingstructuresandhowtoincludeoverloadparametersinthesestructures.

Chapter5,RegularExpressions,exploresPowerShell’simplementationofregularexpressions.Itevaluatesthebuilt-incomparisonoperatorsthatprovideexpressionvalidationandhowtocreatecomplexexpressions.

Chapter6,ErrorandExceptionHandlingandTestingCode,showsyouhowtocreatecodeinarobustmannertoavoidexceptionsduringexecution.Thischapterexplainsvariousbuilt-inerrorandexceptionhandlingtechniques,aswellassupportforlegacysystemsthatdon’tsupportPowerShellcmdlettriggers.Italsoexplainsthedifferentitemstobeawareofduringthetestingcycleofyourcode.

Chapter7,Session-basedRemoteManagement,providesaninsightintosession-basedmanagementthroughPowerShell.Itdisplayshowtoleveragethebuilt-inWinRMtoexecuteitemsonremotesystems.

Chapter8,ManagingFiles,Folders,andRegistryItems,displayshowtoquery,create,modify,anddeleteitemsinthefilesystemandregistry.Thisincludesfiles,folders,registrykeys,registry-namedvalues,andproperties.

Chapter9,File,Folder,andRegistryAttributes,ACLs,andProperties,divesdeepintotheinterworkingoffiles,folders,andregistries.Thischapterexplainshowtosetfileandfolderstandardsandadvancedattributes.ItalsodisplayshowtomanipulateACLstosetpermissionsonfiles,folders,andregistryitems.

Chapter10,WindowsManagementInstrumentation,explainshowtouseWindowsManagementInstrumentation(WMI)toquerylocalandremotesystemsforadvancedsysteminformationandthedifferentcmdletsthatprovideaccesstoasystem’sWMI.

Chapter11,XMLManipulation,exploreseXtensibleMarkupLanguage(XML)andshowsyouhowtointeractwithitusingPowerShell.ThischapterexplainsthedifferentcomponentsthatmakeupaproperXMLdocumentandhowtointeractwiththeseindividualcomponents.

Chapter12,ManagingMicrosoftSystemswithPowershell,providesinformationonhowtoworkwithWindowsusersandgroups,Windowsservices,Windowsprocesses,andthemanipulationofWindowsfeaturesandroles.

Chapter13,AutomationoftheEnvironment,explainshowtoinvokeitemsforusewithautomationscripts.Thischapterexplainsparentandchildrelationshipsbecausetheypertaintolinkingscriptstogether.ItalsoexploresDesiredConfigurationManagement(DCM)andconfigurationbaselines.

Chapter14,ScriptCreationBestPracticesandConclusion,providesbestpracticerecommendationsforutilizingPowerShellinyourenvironment.Thischapterconcludeswithsomefinalthoughtsfromtheauthor.

WhatyouneedforthisbookToworkthroughtheexamplesprovidedinMasteringWindowsPowerShellScripting,youwillneedaccesstoWindows7orahigherWindowsoperatingsystem.YouwillalsoneedServer2008R2orahigherWindowsServeroperatingsystem.ThechaptersinthisbookrelyhighlyonWindowsManagementFramework4.0(PowerShell4.0)andRemoteServerAdministrationTools.Youwillneedtodownloadandinstallbothofthesesoftwarepackagesonthesystemsyouarerunningtheseexampleson.

WhothisbookisforMasteringWindowsPowerShellScriptinghasbeendesignedforPowerShellscripterswhocanbebothbeginnersandadvanced-levelcoders.Byreadingthisbook,youwillbeabletogainin-depthknowledgeofPowerShellandthebestpracticestodevelopscriptsusingthisautomationlanguage.Previousscriptingandcodingexperiencewillbehelpful,thoughitisnotrequired.

ConventionsInthisbook,youwillfindanumberofstylesoftextthatdistinguishbetweendifferentkindsofinformation.Herearesomeexamplesofthesestyles,andanexplanationoftheirmeaning.

Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnames,dummyURLs,userinput,andTwitterhandlesareshownasfollows:“Theget-servicecmdletisusedtoretrievedetailedinformationaboutWindowsservices.”

Anycommand-lineinputoroutputiswrittenasfollows:

#Retrievetheservicesstatusandstarttheserviceifitisstopped.$status=(Get-service–DisplayName"WindowsAudio").StatusIf($status–like"Stopped"){start-service–DisplayName"WindowsAudio"}

Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,inmenusordialogboxesforexample,appearinthetextlikethis:“Toaddafirewallruleonasystemusingthenetshcommand,youneedtoopenPowerShellwiththeRunasAdministratoroption”

NoteWarningsorimportantnotesappearinaboxlikethis.

TipTipsandtricksappearlikethis.

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Chapter1.Variables,Arrays,andHashesPowerShellprovidesavarietyofmechanismstostore,retrieve,andmanipulatedatausedinyourscripts.Thesestorage“containers”arereferredtoasvariables,arrays,andhashes.Theycanbeusedascontainerstostorestrings,integers,orobjects.Thesecontainersaredynamicastheyautomaticallydetectwhattypeofdataisbeingplacedwithinthem.Unlikeotherobject-orientedlanguages,thereisnoneedtodeclarethecontainerpriortouse.Todeclareoneofthesecontainers,youusethedollarsign($)andthecontainername.

Anexampleofacontainerwouldlooklikethis:

$myVariable

Duringthischapter,youwilllearnthefollowingconcepts:

VariablesArraysHashesDecidingthebestcontainerforyourscripts

Whenyouarecreatingnamesforcontainers,itisindustrybestpracticetousenamesthatarerepresentativeofthedatatheyarestoring.WhilecontainersarenotcasesensitiveinPowerShell,itisacommonpracticetousecamelCasewhenwritingcontainernames.camelCaseisachievedbykeepingthefirstletterofthecontainerlowercaseandthesubsequentfirstlettersofeachwordcapitalized.SomevariationsofcamelCasepermitthefirstlettertobecapitalized.Thisformattingaidsineasyreadingofthecontainers.

AnexampleofacontainerusingcamelCasewouldlooklikethis:

$webServerIPAddress

VariablesVariablesareoneofthemostwidelyusedcontainersinPowerShellduetotheirflexibility.Avariableisacontainerthatisusedtostoreasinglevalueoranobject.Variablescancontainavarietyofdatatypesincludingtext(string),numbers(integers),oranobject.

Ifyouwanttostoreastring,dothefollowing:

$myString="MyStringHasMultipleWords"$myString

Theoutputofthisisshowninthefollowingscreenshot:

TheprecedingvariablewillnowcontainthewordsMyStringHasMultipleWords.Whenyououtputthe$myStringvariable,asshownintheprecedingscreenshot,youwillseethatthestringdoesn’tcontainthequotations.ThisisbecausethequotationstellthePowerShellcommand-lineinterpretertostorethevaluethatisbetweenthetwopositionsorquotations.

TipYouareabletoreusevariableswithoutdeletingthecontentalreadyinsidethevariable.ThePowerShellinterpreterwillautomaticallyoverwritethedataforyou.

Subsequently,ifyouwanttostoreanumber,dothefollowing:

$myNumber=1$myNumber


Thismethoddifferentiateswhilestoringastringasyoudonotusequotations.ThiswilltellthePowerShellinterpretertoalwaysinterpretthevalueasanumber.Itisimportanttonotusequotationswhileusinganumber,asyoucanhaveerrorsinyourscriptifthePowerShellinterpretermistakesanumberforastring.

Anexampleofwhathappenswhenyouusestringsinsteadofintegerscanbeseenhere:

$a="1"$b="2"$c=$a+$b$c


The$cvariablewillcontainthevalueof12.ThisisduetoPowerShellinterpretingyour$astringof1and$bstringof2andputtingthecharacterstogethertomake12.

Thecorrectmethodtodothemathwouldlooklikethis:

$a=1$b=2$c=$a+$b$c


Sincethe$aand$bvariablesarestoredasnumbers,PowerShellwillperformthemathonthenumbersappropriately.The$cvariablewillcontainthecorrectvalueof3.

ObjectsstoredinvariablesObjectsarevastlydifferentthanstringsandnumbers.ObjectsinPowerShellaredatastructuresthatcontaindifferentattributessuchaspropertiesandmethodswithwhichonecaninteract.Objectpropertiesaredescriptorsthattypicallycontaindataaboutthatobjectorotherrelatedobjects.Objectmethodsaretypicallysectionsofcodethatallowyoutointeractwiththatobjectorotherobjectsonasystem.Theseobjectscaneasilybeplacedinvariables.Youcansimplyplaceanobjectinavariablebydeclaringavariableandplacinganobjectinit.Toviewalloftheobject’sattributes,youcansimplycallthevariablecontainingtheobject,useapipecharacter|,andusetheget-membercmdlet.

Toplaceanobjectinavariableandretrieveitsattributes,youneedtodothis:

$date=get-date$date$date|get-member

Theoutputisshowninthefollowingscreenshot:

Inthisexample,youwilllearnhowtoplaceanobjectintoavariable.Youfirststartbydeclaringthe$datevariableandsettingitequaltotheoutputfromtheget-datecmdlet.Whenyouexecutethis,theget-datecmdletreferencestheSystem.Dateclass,andthe$datevariableinheritsallofthatobject’sattributes.Youthencallthe$datevariableandyouseethattheoutputisthedateandtimefromwhenthatcommandwasrun.Inthisinstance,itisdisplayingtheDateTimeScriptPropertyattributeonthescreen.ToviewalloftheattributesoftheSystem.Dateobjectinthe$datevariable,youpipethoseresultstotheget-membercmdlet.Youwillseealloftheattributesofthatobjectdisplayedonthescreen.

Ifyouwanttousethepropertiesandmethodattributesofthatobject,youcansimplycallthemusingdotnotation.Thisisdonebycallingthevariable,followedbyaperiod,and

referencingthepropertyormethod.

Toreferenceanobject’spropertiesandmethodattributes,youneedtodothis:

$date=get-date$date.Year$date.addyears("5")


Thisexampleshowsyouhowtoreferenceanobject’spropertiesandmethodattributesusingdotnotation.Youfirststartbydeclaringthe$datevariableandsettingitequaltotheoutputfromtheget-datecmdlet.Whenyouexecutethis,theget-datecmdletreferencestheSystem.Dateclass,andthe$datevariableinheritsallofthatobject’sattributes.YouthenleveragedotnotationtoreferencetheYearpropertyattributebycalling$date.Year.Theattributewillreturn2015astheYearproperty.YouthenleveragedotnotationtousetheAddYears()methodtoincreasetheyearsby5.Afterenteringthe$date.addyears("5")command,youwillseeanoutputonthescreenofthesamemonth,day,andtime;however,theyearisincrementedby5years.

ArraysArraysarethesecondmostusedcontainersinPowerShell.Anarray,insimpleterms,isamulti-dimensionalvariableoravariablecontainingmorethanonevalue.Thetwocorecomponentstoanarrayaretheindexnumberandthepositionvalue.Whenyouuseanarray,youreferenceanindexnumberanditwillreturnthepositionvalue.

Single-dimensionarraysThefollowingtablerepresentsanarraywithasingledimension:

Indexnumber Positionvalue

0 Example1

1 Example2

2 Example3

3 Example4

4 Example5

Whenyouarestoring,manipulating,orreadingthedatainanarray,youhavetoreferencethepositioninthearraythedataisresiding.Thenumberspopulatedinthetable’sIndexnumbercolumnarerepresentativeofthelocationwithinthearray.Youwillseethatarray’snumberingstartsatthenumber0,andsothefirstdatawouldbeincell0.Ifyoucallthearrayatposition0,theresultwouldbethepositionvalueofExample1.Whenbuildingthearray,youwillseethateachvalueinthearrayvaluesisseparatedbyacomma.ThistellsthePowerShellinterpretertosetanewarrayvalue.

First,youcanstartbybuildingthearrayintheprecedingtablebyenteringthefollowingcommand:

$myArray="Example1","Example2","Example3","Example4","Example5"$myArray


Theprecedingexampledisplayshowtocreateanarrayofstrings.Youfirststartbydeclaringavariablenamed$myArray.Youthenplacemultiplestringsoftextseparatedbycommastobuildthearray.Afterdeclaringthearray,youcallthe$myArrayarraytoprintthevaluestotheconsole.ItwillreturnExample1,Example2,Example3,Example4,andExample5.

Retrievingdataataspecificpositioninanarrayisdonethroughtheuseofbrackets.Toretrievethevalueof0fromthearray,youwoulddothefollowing:

$myArray="Example1","Example2","Example3","Example4","Example5"$myArray[0]


Theprecedingexampledisplayshowyoucanobtainarraydataataspecificposition.Youfirststartbydeclaringavariablenamed$myArray.Youthenplacemultiplestringsoftextseparatedbycommastobuildthearray.Afterdeclaringthearray,youcall$myArray[0]toaccessthepositionvalueofindexnumber0fromthearray.TheprecedingexamplereturnsthevalueofExample1fortheindexnumber0.

JaggedarraysArrayscanbecomemorecomplexasyoustartaddingdimensions.Thefollowingtablerepresentsajaggedarrayoranarrayofarrays:

Indexnumber Positionvalue0 Positionvalue1

0 Example1 Red

1 Example2 Orange

2 Example3 Yellow

3 Example4 Green

4 Example5 Blue

Whileaccessingdatainajaggedarray,youwillneedtoreadthecellvaluescountingat0forbothdimensions.Whenyouareaccessingthedata,youstartreadingfromtheindexnumberfirstandthenthepositionvalue.Forexample,theExample1dataisintheindexnumberof0andthepositionvalueof0.Thiswouldbereferencedasposition[0][0].Subsequently,thedataBlueisintheindexnumberof4andpositionvalueof1.Thiswouldbereferencedasposition[4][1].

Todothisforyourself,youcanbuildtheprecedingtablebyenteringthefollowingcommand:

$myArray=("Example1","Red"),("Example2","Orange"),("Example3","Yellow"),("Example4","Green"),("Example5","Blue")$myArray[0][0]$myArray[4][1]

Theoutputisshowninthefollowingscreenshot:

Thisexampledisplayshowtocreateajaggedarrayandaccessingvaluesinthearray.Youfirststartbuildingthejaggedarraybydeclaringthefirstarrayof"Example1""Red",secondarrayof"Example2""Orange",thirdarrayof"Example3""Yellow",fourtharrayof"Example4""Green",andfiftharrayof"Example5""Blue".Afterbuildingthearray,youaccessthewordExample1byreferencing$myArray[0][0].YouthenaccessthewordBluebyreferencing$myArray[4][1].

UpdatingarrayvaluesAfteryoucreateanarray,youmayneedtoupdatethevaluesinsidethearrayitself.Theprocessforupdatingvaluesinanarrayissimilartoretrievingdatafromthearray.Firstyouneedtofindthecelllocationthatyouwanttoupdate,andthenyouneedtosetthatarraylocationasequaltothenewvalue:


0 John Doe

1 Jane Smith

Giventheprecedingtable,ifJane’slastnameneededtobeupdatedtodisplayDoeinsteadofSmith,youwouldfirstneedtolocatethatdatarecord.Thatincorrectlastnameislocatedatindexnumber1andpositionvalue1,or[1][1].Youwillthenneedtosetthatdatalocationequal(=)toDoe.

Todothis,youneedtoenterthefollowingcommand:

$myArray=("John","Doe"),("Jane","Smith")$myArray$myArray[1][1]="Doe"$myArray


Thisexampledisplayshowyoucancreateanarrayandupdateavalueinthearray.Youfirststartbydefining$myArrayanduse"John","Doe","Jane",and"Smith"asthearrayvalues.Aftercallingthevariabletoprintthearraytothescreen,youupdatethevalueinindexnumber1,positionvalue1,or$myArray[1][1].BysettingthispositionequaltoDoe,youchangethevaluefromSmithtoDoe:


0 John Doe

1 Jane Smith

2 Sam Smith

Ininstanceswhereyouwanttoappendadditionalvaluestothearray,youcancallthearrayvariablewiththe+=commandandthedatayouwanttoaddtothearray.Thislookslike$array+="NewArrayValues".The+=commandisamoreefficientmethodofperformingthecommands$array=$array+"NewArrayValues".

Toadddataintoanarrayandmaketheprecedingtable,youcandothefollowingoperation:

#CreatetheArray$myArray=("John","Doe"),("Jane","Smith")$myArray#AppendDatatotheArray$myArray+=("Sam","Smith")$myArray


Inthisexample,youaddvaluestoanexistingarray.Youfirststartbydefininganarrayof$myArray.Youthenprinttheexistingcontentsofthearraytothescreen.Youthenaddadditionalcontentbysettingthearray+=tothenewarraydataof("Sam","Smith").Afterreprintingthecontentsofthearraytothescreen,youseethevaluesSamandSmithaddedtothearray.

TipTosearchandremoveitemsfromanarray,youwillneedtocreateaForEachlooptocyclethroughalloftheindexnumbersandpositionvalues.Chapter4,Functions,Switches,andLoopStructures,explorestheForEachloopingstructure.

HashesHashesareusedlikearrays.Themaindifferenceisthattheyusethevaluesasindexesversussequentiallynumberedindexes.Thisprovideseasyfunctionalitytoadd,remove,modify,andfinddatacontainedinthehashtable.Hashtablesareusefulforstaticinformationthatneedsadirectcorrelationtootherdata:

Name Value

John.Doe Jdoe

Jane.Doe jdoe1

AgoodexampleofahashtablewouldbeintheinstanceofanActiveDirectorymigration.InmostActiveDirectorymigrations,youwouldneedtocorrelateoldusernamestonewusernames.Theprecedingtablerepresentsausernamemappingtableforthesetypesofmigrations.Whileatraditionalarraywouldwork,ahashtablemakesthismucheasiertodo.

Tocreatetheprecedinghashtable,enterthefollowingcommand:

$users=@{"john.doe"="jdoe";"jane.doe"="jdoe1"}$users


Afteryoucreatethetable,youmaywanttofindaspecificuser.Youcansearchahashtablebyusingthehash’sindexingfunction.Thisisdonebycalling$hashName["value"].Anexampleofthiswouldlooklikethefollowingcommand:

$users=@{"john.doe"="jdoe";"jane.doe"="jdoe1"}$users["john.doe"]


Afterenteringthecommand,youwillseethat$users["john.doe"]returnsjdoeasthecorrelatingvalueinthehash.

Oneofthemostpopularmethodstousewithhashtablesistheaddmethod.Theadd

methodallowsyoutoenternewvalueswithinthehashtable.Youcanusethiswhilebuildingthehashtable,asmosthashtablesarebuiltwithinascript.Ifyouwanttoaddanotherusertothehashtable,usetheaddmethodasshownhere:

$users=@{"john.doe"="jdoe";"jane.doe"="jdoe1"}$users$users.add("John.Smith","jsmith")$users


YouwillseethatJohn.Smithwiththevalueofjsmithisnowaddedtothehashtable.

Youcanalsoupdatevaluesinahashbyleveragingthehash’sindex.Thisisdonebysearchingforavalueandthensettingitscorrelatinghashvalueequaltoanewvalue.Thislookslike$arrayName["HashIndex"]="Newvalue".Anexampleofthisisgivenhere:

$users=@{"john.doe"="jdoe";"jane.doe"="jdoe1"}$users$users["jane.doe"]="jadoe"$users


YouwillseethatthemappedvalueforJane.Doenowreadsjadoe.Thisisvastlydifferent

fromanarray,whereyouwouldhavetosearchforaspecificvaluelocationtoreplacethevalue.

Ifyouwanttoremoveauserfromthehashtable,usetheremovemethod,asshownhere:

$users=@{"john.doe"="jdoe";"jane.doe"="jdoe1"}$users$users.remove("Jane.Doe")$users


YouwillseethatJane.Doeisnowremovedfromthehashtable.Thismethodishelpfulwhenyouneedtoremovespecificvalues,whichmeetcertaincriteria,fromthehashtable.

DecidingthebestcontainerforyourscriptsWhenyouarescripting,itisimportanttoputconsiderationintowhatkindofcontaineryouwillbeusing.Sometimesthesimplicityofcreatingasingularvariableandupdatingthatvariableislesscomplexthancreatinganarrayorhashtabletosearchthrough.Atothertimes,itmaybemoreefficienttopullthewholedatasetanduseindividualpiecesofthatdatawithinyourscript.

Single-linevariablescanbeusedfor:

MathoperationsthatrequirecalculationsofsingleormultiplevaluesCatchingsingle-lineoutputfromexecutinganon-PowerShellcommandTrackingcurrentpositioninalooplike“percentcomplete”

Arraysarebestusedfor:

StoringalistofitemsforindividualprocessingwithinascriptDumpingerrorinformationfromaPowerShellcmdlet

Hashesarebestusedfor:

MappingdatafromonevaluetoanothervalueDatathatrequiresfrequentsearching,updating,orbuildingduringscriptexecutionStoringmultiplevaluesofcorrelateddatalikeuserobjectattributes

SummaryThischapterexplorestheuseofavarietyofcontainers.Youlearnedthatvariables,arrays,andhasheshavethecommonalityofbeingabletostoredata,buttheydoitindifferentways.Youlearnedthatdifferenttypesofdatacanbestoredinthesecontainers.Thesetypesofdataincludenumbers,strings,andobjects.

Thischapterexploredthatvariablesarebestusedforthestorageofsingle-dimensionaldatasets.ThesedatasetscancontainstringsbutalsoincludemathematicalequationsthatPowerShellhastheabilitytoinherentlycalculate.Youalsonowknowthatarraysareprimarilyusedinsituationswhereyouwanttostoremorethanonesetofdata.Youareabletonavigate,add,andremovevaluesinthearraybasedoffofastartingvalueof0.Last,youlearnedthathashesarebestusedwhilecorrelatingdatafromonevaluetoanother.Youareabletoadd,remove,andsearchdatacontainedinthehashtableswiththeuseofsimplecommands.Inthenextchapter,youwilllearntechniquestoperformdataparsingandmanipulationbyleveragingvariablesandarrays.

Chapter2.DataParsingandManipulationOneofthemostpowerfulfeaturesofPowerShellisitsabilitytoretrieveandmanipulatedata.ManyatimeswhenyouretrievedatafromaPowerShellsession,theformatinwhichitisavailableisdifferentfromwhatyouwouldwanttodisplayinthePowerShellwindoworinalogfile.Forthispurpose,PowerShellprovidespowerfulcmdletsandmethodstoperformdatamanipulationtobestsuityourneedsasaPowerShellscripter.

Whilereadingthischapter,you’lllearnthefollowingconcepts:

StringmanipulationNumbermanipulationandparsingDate/timemanipulationForcingdatatypesPowerShellpipeline

StringmanipulationStringmanipulationissomethingthatyou’llneedtodoinalmosteveryscriptyoucreate.Whilesomeofthestringmethodswillbeusedmoreoftenthanothers,theyallservedifferentpurposesforyourscript.Itisultimatelyuptoyourcreativityonhowyouwantdatatolookwhenitisdisplayedonthescreen.

Tochangethetexttouppercase,executethefollowingcommand:

$a="Error:Thisisanexampleerror"$a.toUpper()


ThetoUpper()methodisusedtoformatthetexttouppercase.Thisishelpfulinsituationswheremessagesneedtobeemphasizedorshouldstandout.Theresultofthiscommandwillchangethecase.

Tochangethestringtolowercase,executethefollowingcommand:

$string="TheMACAddressis"$mac="00:A0:AA:BB:CC:DD"$message=$string+$mac.toLower()$message


TheinverseoftoUpper()istheuseoftoLower().Thiscommandwillconverttheentirestringtolowercaseintheinstancewhenyoudonotwanttoemphasizeastring.toLower()istypicallyusedinsituationswhereasinglewordoravariableisuppercase,andyouwanttotransitionittolowercase.Thiscommandshowstakingtwoseparatestrings,formattingthe$MACstringtothelowercase,andoutputtingbothvariablestogether.

ReplacingandsplittingstringsPowerShellalsoprovidestheabilitytoreplacecharactersinstringsusingtheReplace()method.Thisisusefulwithinyourscriptswhenyouhavetoreplacecharactersfromtheoutputofanothermethod.Forinstance,ifyoupullalistofcommonusernamesfromActiveDirectory,theyareprefixedwithcn=.IfyouwantedtoreplaceCN=withnothing(""),youcaneasilyaccomplishthiswiththeReplace()method.

Toreplaceitemsinastring,executethefollowingcommand:

$usernames="CN=juser,CN=jdoe,CN=jsmith,CN=bwhite,CN=sjones"$usernames=$usernames.replace("CN=","")$usernames


ThisscriptwillreplacethecharactersCN=withnothingasdesignatedby"".Theoutputofthisscriptisalistofusernameswithcommaseparators.Asyoucansee,thisisveryhelpfulinthemanipulationofthedatabeingoutputfromActiveDirectory.Buildingonthepriorexample,ifyouwantedtoprocesstheusernamesindividually,youcanleveragethesplit()method.Thesplit()methodwillseparatevaluesinastring,bydeclaringaspecificcharactertosplit.

Tosplititemsinastring,executethefollowingcommand:

$usernames="juser,jdoe,jsmith,bwhite,sjones"$userarray=$usernames.split(",")$userarray


Whenyouleveragethesplit()method,asshowninthisexample,thescriptusesthecommaasdesignationthatthenextitemneedstobeanewvaluewithinthearray.Theoutputfromthisscriptallowsyoutointeractwiththeseusernamesindividually.Youwillfrequentlyusethesplit()methodwhileworkingwithcommaseparatedvalues(CSV)filesorXMLfiles.It’scommonforthesetypesoffilestocontainmultipleobjectsperline,whichmakessensetoleveragethesplit()method.

CountingandtrimmingstringsPowerShellhastwomethodstocountobjectswithinvariablesandarrays.ThefirstisdonebyusingtheCountmethod.TheCountmethodisusedtocountthenumberofobjectsthatarecontainedwithinanarray.Thisisusefulwhenyouareattemptingtodeterminethequantityofitemsyou’llbeprocessingwithinyourscript.

Tocountitemsinanarray,executethefollowingcommand:

$services=get-service$services.count


Agoodexampleofdetermininghowmanyobjectsarepresentinanarrayisobtainingthenumberofservicesrunningonasystem.ThepreviouscommanddisplaysaqueryoftheservicesonaboxandusestheCountmethodtoobtainthequantityofservices.Thesysteminthisexamplehas210services.

Thesecondmethodtocountobjectsisusedforinstancesinyourscriptswhereyouneedtodeterminethelengthorthenumberofcharactersinastring.ThisiscompletedbyusingtheLengthmethod.TheLengthmethodwillcountthenumberofcharactersinastring,includingspaces,andoutputthequantityofcharacters.

AcommonscenariowhereyouwouldusetheLengthmethodiswithWindowsfileandfolderpaths.SincetheWindowsoperatingsystemsarewellknownforhavingafilepathlimitationof255characters,wecanleveragetheLengthmethodtoqualifyincaseswherethepathisoverthatlimitation.

Togetthelengthofastring,executethefollowingcommand:

$path="c:\windows\system32\drivers\1394bus.sys"$path.length


Inthisexample,youarecountingthenumberofcharactersinafileandfolderpathtoensurethatyoudonotexceedthemaximumnumberofcharacters.Thiscommandcountedthelengthof$pathtobe39characters.Throughthiscommand,you’vedeterminedthatitisnotoverthelimitationsoftheWindowsoperatingsystem.

TheTrimmethodAsyouscript,you’llrunintosituationswheretheoutputfromacommandortheinputfromafilemaynotbeinaformatthatcanbeeasilyparsed.Forexample,ifyouimportvaluesfromaCSVfileandthosevalueshaveextraspaces,itcancauseyourscripttofail.PowerShellprovidestheabilitytotrimstringsofspacesandothercharacterswiththeTrim()method.TheTrim()methodcomesinthreedifferentvariations,whichareTrim(),TrimStart(),andTrimEnd().

Totrimthespacesoutofastring,usethefollowingcommand:

$csvValue="servername.mydomain.com"$csvValue.trim()


Bydefault,whenyouusetheTrim()methodwithoutdeclaringanycharacterstotrim,itwillautomaticallyremovethespacesthatsurroundthetextvaluesinastring.Thisexampledisplaysacomputernamethatissurroundedbyspaces.AfterrunningtheTrim()method,you’llseethatthespacesaresuccessfullytrimmedfromthestring.

Totrimvaluesoutofastring,executethefollowingcommand:

$csvValue="servername.mydomain.com"$csvValue=$csvValue.trim(".mydomain.com")$csvValue


Ifyouwanttotrimaspecificvaluefromastring,youcandeclareitwithintheTrim()method.Byexecutingtheprecedingscript,you’llseethatdeclaringatextvalueof.mydomain.comwithintheTrim()methodwillremovethosecharactersfromtheentirestring.

TheTrimStart()methodprovidesthesamefunctionalityoftheTrim()method;however,itonlyremovescharactersfromthebeginningofthestring.Likewise,theTrimEnd()methodwillonlyremovecharactersfromtheendingofthestring.Thesearehelpfulinsituationswhereyouneedtoparsethedataintovaluesthatcanbereadeasily.

Totrimthebeginningandendofastring,executethefollowingcommand:

$csvValue="FQDN:servername.mydomain.com"

$csvValue=$csvValue.trimStart("FQDN:")$csvValue=$csvValue.trimEnd(".mydomain.com")$csvValue


TheprecedingexampledisplaystheuseofbothTrimStart()andTrimEnd()methods.Inthisexample,youtrimthe"FQDN:"charactersfromthestartofthestringand.mydomain.comfromtheendofthestring.Thefinaloutputofthisisservername.

WhenyouusetheTrim()method,you’llwanttorememberthatitwillremoveallinstancesofthewordsfoundatthebeginningandendingofthestring.Ifyouusedcomputernameinsteadofservername,youwouldhavenoticedthattheoutputfromthemethodwouldhaveputername.TheTrim()methodwouldhavematchedthewordscomandremoveditfromthestring.ItisbesttousetheTrim()methodtoremovespacesandunneededcharactersinstrings.UsetheReplace()methodtoremoveseriesofstringssuchas.mydomain.com.

Thiswouldlooklikethis:

$csvValue="computername.mydomain.com"$csvValue.Trim("com")


TheprecedingexampledisplayshowtheTrim()methodwillremovestringsfromthefrontandtheendofastring.Youfirstneedtostartbydeclaringthe$csvValuevariableasequaltocomputername.mydomain.com.YouthenneedtoleveragetheTrim()methodonthevariablesearchingforthewordcom.You’llseethatthemethodtrimsboththebeginningcomandendcomonthestringitself.Theendresultisputername.mydomain.

TheSubstringmethodTheSubstring()methodisanotherstringmanipulatorwithinthePowerShelltoolset.Itisbasedontherequirementthatyoumaywanttoremovecharacterspresentatafixedpositionwithinastring.ThefollowingtabledisplaysthestringpositionsforthestringTESTING123.Likeanarray,thestringpositionstartscountingat0,asshownhere:

Stringposition 0 1 2 3 4 5 6 7 8 9

Stringvalue T E S T I N G 1 2 3

Toobtainasubstringfromastring,executethefollowingcommand:

$string="TESTING123"$string=$string.substring("7")$string


TheSubstring()methodisdesignedtoextractdatapresentatspecificlocationsinastring.Ifyouwantedtoextractthenumbers123fromtheprecedingtable,youcanusetheSubstring()methodreferencingthestartpositionof7.Alloftheremainingcharactersafterposition7willbedisplayedandtheoutputofthemethodis123.

Toobtainasubstringrangefromastring,executethefollowingcommand:

$string="TESTING123"$string=$string.substring("0","4")$string


TheSubstring()methodallowsyoutoenterasecondvaluewithinthemethod.Whilethefirstvaluedesignatesthestartposition,thesecondvaluedesignateshowmanycharactersafterthestartpositionyouwanttoinclude.Inthepreviousscriptexample,thescriptstartsatposition0andcounts4spacesafterthepositionof0.TheresultofthiscommandisTEST.

ThestringtrueandfalsemethodsPowerShellhasbuilt-instringsearchingcapabilitiesthatprovideyouwiththeabilitytoquicklydeterminewhetherastringcontainsaspecificvalue.ThethreemethodsthatcanperformthesearchinginastringareContains(),Startswith(),andEndswith().Allofthesemethodsarebasedonthesameprinciple,thatis,findingaspecificvalueandreportingTrueorFalse.

Toseewhetherastringcontainsavalue,dothis:

$ping=pingThisDoesNotExistTesting.com–r1$ping$deadlink=$ping.contains("Pingrequestcouldnotfindhost")$deadlink


Thisexampleleveragesthepingcommandtodeterminewhetheraspecificwebsiteorhostisalive.Inourexample,youcapturethepingcommandinthe$pingvariable.YouthensearchthatvariablefortextthatmatchesPingrequestcouldnotfindhost.Astheoutputfromthepingcommandreturnsthevalueyouarelookingfor,theContains()methodwillreturnTrueandthe$deadlinkvariableissettoTrue.

Toseewhetherastringstartswithavalue,executethefollowingcommand:

$ping=pingThisDoesNotExistTesting.com–r1$ping$deadlink=$ping.StartsWith("Pingrequestcouldnotfindhost")$deadlink


WhenyourunthesamescriptwiththeStartswith()method,itwillreturnthesameresultofTrue.ThatisbecausethevaluethatyouaresearchingforstartswithPingrequestcouldnotfindhost.

Toseewhetherastringendswithaspecificvalue,executethefollowingcommand:

$ping=pingThisDoesNotExistTesting.com–r1$ping

$deadlink=$ping.EndsWith("Pleasecheckthenameandtryagain.")$deadlink


WhenyourunasimilarscriptwiththeEndswith()method,itwillreturntheresultofTrue.ThatisbecausethevaluethatyouaresearchingforendswithPleasecheckthenameandtryagain.

NumbermanipulationandparsingPowerShellisapowerfulmathematicscalculator.Infact,PowerShellhasanentireWindowsclassdedicatedtomathematicscalculationsthatcanbecalledbyusingthe[System.Math].NETclass.Whenyouareworkingwiththe[System.Math]classes,itiscommontocallstaticfieldswithinaclass.Staticfieldsarestaticproperties,methods,andobjectsthatcanbecalledtodisplaydataordoactions.Tocallastaticfield,youcallthe[Math](shortenedversionof[System.Math])class,followedbytwocolons::andthestaticfieldname.

Tousethemathoperationtocalculatepi,executethefollowingcommand:

[math]::pi


ThissimplecommandwillprovidePIifyoueverneeditforacalculationbyusingthepimethodofthemathclass.Theresultofthiscommandreturns3.14159265358979.

TousethemathoperationtocalculateEuler’snumber,executethefollowingcommand:

[math]::e


Likewise,ifyoueverneedtoreferenceEuler’sNumber(e),youcanachievethisbyleveragingtheemethodofthemathclass.Theresultofthiscommandreturns2.71828182845905.

Tocalculatethesquarerootofanumber,executethefollowingcommand:

[math]::sqrt("996004")


Ifyouneedtocalculatethesquarerootofalargenumber,youcanusethesqrtmethodofthemathclass.Theresultofthiscommandreturns998.

Toroundanumber,executethefollowingcommand:

$number="214.123857123495731234948327312341657"[math]::Round($number,"5")


Roundingisverycommonforintegersinyourscripts.WhenyouwanttousetheRound()method,you’llhavetospecifyanumberandthenumberofdigitsyouwanttorounditto.Inthiscommand,youtakethenumberof214.123857123495731234948327312341657androundittothefifthdigit.Theresultofthiscommandreturns214.12386.

FormattingnumbersWhilePowerShellcanperformmathematicsverywell,itdoesnothaveanynativecommandsfortheformattingofnumbers.Inordertoformatnumbers,you’llneedtoleveragePowerShell’sabilitytousethe.NETFramework’sformattingmethods.Theconstructforthe.NETFrameworkformatmethodsiscalledbyspecifying"{StartingCharacter:FormatTypePrecision}"–f$variable.Thestartcharacteristhepositionwhereyouwanttostartformattingthenumber.Themostcommonformattypesarecurrency(C),decimal(D),numeric(N),percentage(P),andhexadecimal(X).Theprecisionfieldisthenumberofdecimalplacesyouwantthenumbertobeaccurateto.

Toformatyournumberinanumericformatting,executethefollowingcommand:

$number=12375134.132412"{0:N4}"–f$number


Inthisexample,youaretakingthe12375134.132412numberandformattingitinnumericformatstartingatthefirstcharacter.Thiscommandalsoroundsthenumbertothefourthdigit.

Toformatanumbertomakeithexadecimal,executethefollowingcommand:

$number=12375134$number="{0:X0}"–f$number$number


Ifyouwanttoconvertanintegertohexadecimal,youcanformattheintegertohexadecimalbyspecifying"{0:X0}"–f$number.TheoutputofthiscommandisBCD45E.Itisimportanttorememberthathexadecimalonlysupportsformattingfromwholenumbers.Ifyoudonotusewholenumbers,thescriptwillfailduetoitbeinginaninvalidformat.

FormattingbytesPowerShellhastheabilitytodirectlyconvertnumberstokilobytes(KB),megabytes(MB),gigabits(GB),andterabytes(TB)throughpredefinedaliasesforconversions.Thisishelpfulwhenyouarepullingdatavalues,whichbydefault,areformattedinbytes.Someofthesemayincludediskspaceandmemoryonasystem.Theuseofthealiasisnumberinbytesdividedbyoneunitofmeasure.

ToformatbytestoKB,MB,GB,andTB,usethefollowingoperations:

#16GBofMemoryinBytes$ComputerMemory=16849174528$ComputerMemory/1TB$ComputerMemory/1GB$ComputerMemory/1MB$ComputerMemory/1KB


Whenyouexecutetheprecedingscript,PowerShellwilltakethememorysizeofacomputerinbytesandconvertittoterabytes,gigabytes,megabytes,andkilobytes.Asyoucansee,PowerShellprovidesaquickabilitytodeterminedatacalculationsusingthepredefinedaliases.

DateandtimemanipulationWhenyouarescripting,therearetimeswhereyoumayneedtogetthedateandtimeofasystem.PowerShellofferstheget-datecmdlet,whichprovidesthedateandtimeinmanydifferentformatsofyourchoice.

Toobtainthedateobject,executethefollowingcommand:

$time=get-date$time


Thestandardget-datecmdlet,withoutanytriggers,willgeneratethelongdateandtimeformat.Whenyoustorethedateobjectinavariable,itisimportanttorememberthatthedatacapturedfromthecmdletisasnapshotintime.You’llhavetocalltheget-datecmdletagaintogetnewvaluesfortheupdateddateandtime.

Thefollowingtabledisplaysallofthedatetimeformattingcodes:

Formatcode Result Example

MM Monthinnumericformat 04

DD Dayinnumericformat 15

YYYY Yearinnumericformat 2014

HH Hourinnumericformat(24hrs) 14

hh Hourinnumericformat(12hrs) 02

mm Minutesinnumericformat 15

ss Secondsinnumericformat 12

tt AM/PM(12hr) PM

Whenyoucalltheget-datecommand,youalsohavetheabilitytoformatitinmultiplewaysusingthe–formatproperty.Theprecedingtabledisplaysdifferentformattingoptionsyoucanusetocreateyourowndatetimeformat.Thesevaluesarecase-sensitive.

Toformatthedateobjecttospecificvalues,executethefollowingcommand:

$date=get-date–format"MM/dd/yyyyHH:MM:sstt"$date


Thepreviouscommanddisplayshowyouleveragetheget-datecmdletwiththe-formattrigger.Whenyouexecutethecommand,itreturnsthevaluesforthemonth,day,year,hours,minutes,seconds,andtheAM/PMindicator.Asyoucansee,youcanleveragethedatetimeformattinginconjunctionwithstringsandothercharacterstocreatethetimeformatyoudesire.

Toformatthedateobjectandinsertitbetweenstrings,youcanexecutethefollowingcommand:

$date=get-date–format"MMddyyyyHHMMss"$logfile="Script"+$date+".log"$logfile


Theprecedingexampledisplayshowyoucanleveragetheget-datecmdlet,withthe-formattriggertogenerateanameforalogfile.ThisishelpfulinsituationswhereyoumayhavetorunacommandinPowerShellfrequently,andyouhavetolabeltheexecutiontime.Theprecedingscriptwillgeneratethedateandtime,appendthewordScriptinfront,and.logattheendofthestring.Theresultingfilenamefromthisisunique.

Toadddaysusingthedateobject,executethefollowingcommand:

$date=(get-date).AddDays(30).ToString("MM/dd/yyyy")$date


Theget-datecmdletisalsorobustenoughtobeabletoperformmathoperationswithdates.Theprecedingexamplewilltakethecurrentdate,add30daystoit,andsetittothe$datevariable.YoucanalsouseAddYears(),AddMonths(),AddHours(),AddSeconds(),AddMilliseconds(),andAddTicks()toincreasethetime.Ifyouwanttousesubtraction,youcanenteranegativevalueinthemethodanditwillsubtractthatvaluefromthemethods.ThiswouldlooklikeAddDays(-30)tosubtract30days.

NoteFormoreinformationondatetimeformattingvalues,youcangotohttp://technet.microsoft.com/en-us/library/ee692801.aspx.

Thelastformattingtechniqueimportantforscriptingisconvertingsystemtime/tickstolegibletimeformats.Thisisachievedbycallingthe[DateTime]classandleveragingtheFromFileTimemethod.Theprecedingexampledisplaysformattingtheticknumberof130752344000000000,leveragingthe[DateTime]class,andformattingittoMonday,May04,20151:33:20PM.ThisisusefulforsystemattributesthatareonlydisplayedintickformatsuchasLastLogonTimestamporLastBootUpTime.

Toconvertfiletimetoadifferentformat,executethefollowingcommand:

$date=[datetime]::FromFileTime("130752344000000000")$date


Theprecedingexampledisplayshowtotakesystemticksandconvertthemintoalegibledatetimeformat.Youfirststartbydeclaringa$datevariable.Youthencallthe[datetime]classandreferencetheFromFileTimestaticfiled.Youfeedtheticktimeof130752344000000000intothestaticfiled.Thisformatstheticktimetothedefaultdatetimeformatandstoresthevalueinthe$datevariable.Youthencallthe$datevariable,andyouseetheconvertedvalueofMonday,May04,20151:33:20PM.

http://technet.microsoft.com/en-us/library/ee692801.aspx

ForcingdatatypesWhiledevelopingscripts,youmayrunintoinstanceswhereyoumaywanttoforceaspecificdatatype.ThisishelpfulincaseswherePowerShellautomaticallyinterpretstheoutputfromacommandincorrectly.Youcanforcedatatypesbytheuseofbracketsspecifyingadatatypeandavariable.

Toforceastringdatatype,executethefollowingcommand:

[string]$myString="ForcingaStringContainer"$myString


Theprecedingcommandforcesthestringdatatypetothe$myStringvariable.Theresultisthatthe$myStringvariablewillalwaysremainastring.Itisimportanttoknowthatiftheobjectoritemthatyouaretryingtoforcetoadatatypedoesn’thaveadirectconversiontothatdatatype,itwillthrowanerrororexception.Thiswouldbethecaseifyoutrytoinsertastringintoanintegerdatatype.

Toforceastringdatatypeandgenerateadataexception,executethefollowingcommand:

[int]$myInt="TryingtoPlaceaStringinanIntContainer"


Theprecedingexampledisplaystryingtoinsertastringintoan[int]datatype.Youfirststartbyforcingthe$myIntvariabletobea[int]datatype.Youthentrytosetthatequaltoastringvalueof"TryingtoPlaceaStringinanIntContainer".Afterenteringthecommand,youimmediatelyreceiveanexceptionofCannotconvertvalue"TryingtoPlaceaStringinanIntContainer"totypeSystem.Int32.Thisexampleshowsthatyoucannotmixandmatchdatatypesthatdonothavedirectconversionstoeachother.

ThereareavarietyofdatatypesthatyoucanforcewithinPowerShell.ThefollowingtablerepresentsthecommondatatypesforusewithPowerShellandanexplanationandanexampleofitsuse:

Datatype Explanation Example $avalue

[string] StringofUnicodecharacters [string]$a="Hello" Hello

[char] AUnicode16-bitcharacter [char]$a=0xA9 ©

[byte] An8-bitcharacter [byte]$a=0x0001D 29

[int] 32-bitinteger [int]$a=12345 12345

[long] 64-bitinteger [long]$a=1234.243 1234

[bool] BooleanTrue/Falsevalue [bool]$a=1 True

[decimal] A128-bitdecimal [decimal]$a=1234.243 1234.243

[single] Asingle-precision32-bitnumber[single]$a=1234.243 1234.243

[double] Adouble-precision64-bitnumber[double]$a=1234.243 1234.243

[datetime] Adatatimevalue [datetime]$a="01-APR-2014" Tuesday,April1,201412:00:00AM

[xml] AXML-styledvalue[xml]$a="Testing"

$a.test.aTesting

[array] Anarray-styledvalue [array]$a=1,2,31

2

3

[hashtable] Ahashtable-styledvalue [hashtable]$a=@{"Old"="New"}Name

--------

Old

Value

--------

New

PipingvariablesTheconceptofpipingisn’tanythingnewtothescriptingworld.Piping,bydefinition,isdirectingtheoutputofanobjecttoanotherobject.WhenyouusepipinginPowerShell,youaretakingtheoutputofonecommandandsendingthedataforusewithanothersectionofcode.Themanipulationcanbeeithertoamorelegibleformat,orcanbebyselectingaspecificobjectanddiggingdeeperintothoseattributes.Apipeisdesignatedbythe‘|‘symbolandisusedafteryouenteracommand.Theconstructofapipelookslikethis:command|ResultManipulation|SortingObjects.Ifyouneedtoaccesstheindividualitemsinthepipeline,youcanleveragethepipelineoutput$_command.Thistellsthepipelinetoevaluatetheresultsfromthepipelineandtheirattributes.

Thepipelineoffersawidevarietyofuses;youcanleveragecommandssuchassort-objecttosortbyaspecificattribute,format-listtoformattheobjectsintoalist,andeventheselect-objectwhereyoucanselectspecificattributestoformthepipelineforadditionalprocessing.Select-objectalsoallowsyoutoleveragethe–firstand–lastparameterswithanumbertoselectarecordsetfromthebeginningorendingofthepipeline.Anotherpopularcommandisthewherecommand,whichallowsyoutowriteanexpressiontoselectitemsinthepipelinethatmeetcertaincriteria.

Topipevaluesfromacmdlet,executethefollowingcommand:

$services=get-service|where{$_.name–like"*Event*"}|Sort-objectname$services


Thisexampledisplaystheuseofpipingtheget-servicescmdlet.Itstartsbygettingalltheservicesonasystem,theuserthenpipesthoseresultstotheselectioncriteriawheretheobject’snameislikethewordevent,whichthenpipesthoseresultstothesortingofobjectsinalphabeticalorderbytheirnameproperty.TheoutputisonlytheserviceswiththenamesthatcontainEventinalphabeticalorder.

Toobtainallfilesthatarelargerthanaspecificsize,executethefollowingcommand:

$largeFiles=get-childitem"c:\windows\system32\"|where{$_.length–gt20MB}$count=$largeFiles.countWrite-host"Thereare$countFilesover20MB"write-host"FilesOver20MBinc:\Windows\System32\:"$largefiles|select-objectname,length,lastwritetime|format-list


Whenyouleveragethepipecommand,youhavetheabilitytofindspecificdatapertainingtoanobject.Inthisexample,yousearchallofthefilesinc:\windows\system32todeterminewhetherthereareanyfilesthathaveasizegreaterthan20MB.Youwereabletopipetheget-childitemcmdlettothewhereoperatorwiththeselectioncriteria$_.lengthisgreaterthan20MB.Theseresultswereplacedinthe$largeFilesvariable.Fromthere,youusethecount()methodtocountthenumberoffilesthatarelargerthan20MB.YouthenprinttoscreenthetextThereare$countfilesover20MB.YoualsoprinttothescreenFilesover20MBinc:\Windows\System32\:toprovidetextforthefollowingpipedcommand.Youthenneedtotaketheresultsinthe$largeFilesvariableandpipetheresultstotheselect-objectcommandtoselectthename,length,andlastwritetime.Finally,youpipethoseresultstotheformat-listcommand,whichprovidesaformattedlistofresults.

SummaryThischapterexploresthemanymethodsyoucanusetomanipulateandparsedatawithPowerShell.Youlearnedtechniquesthatwillhelpyoubetterworkwithdataandprovidearicherexperienceforindividualsusingyourscripts.

Thestringmanipulationsectiontaughtyoumanydifferentmethodstoworkwithstrings.Thisincludedchangingthecase,splittingandreplacingstrings,countingandtrimmingstrings,searchingstrings,andviewingsubstrings.ThenumbermanipulationsectiontaughtyouhowtousemathematicaloperationswithinPowerShell.Thissectiondisplayeddifferentwaystoformatnumbers,roundnumbers,andcalculatingcomplexmathematicaloperations.Thedatetimesectionofthischapterprovidedyouwithtoolstousewhenyouneedtogatherdateandtimeinformationfromasystem.Youlearnedhowtoformattheget-datecmdlet,manipulatetheresults,andaddorsubtractfromdatevalues.

Thischapteralsoexploredtheforcingofdatatypeswhileworkingwithvariables.Thissectionprovidedexamplesofdifferentdatatypesthatareavailabletouse,andprovidedanexampleonhowtoforceaspecificdatatype.Youthenwrappedupwithanexplanationonpipingandhowtoconstructproperpipingclauses.Itexploredhowtoleveragepipingtosortdataafteraresultisreturnedandprovidedexamplesofpipingwithandwithoutadatasort.

DataparsingandmanipulationisessentialtosuccessfulscriptingwithPowerShell.Withoutusingthesemanipulationtechniquesinthischapter,youmaybeoverlycomplicatingyourscripts.Whileitmaytaketimetofullylearnthesetechniques,it’sessentialtobecomeagoodPowerShellscripter.Inthenextchapter,you’lllearnhowthemanipulateddatayougeneratecanbecorrelatedtoseewhetheritmatchescertaincriteria.You’lllearnthatthecomparisonsaredonewiththeuseofcomparisonoperators.

Chapter3.ComparisonOperatorsPowerShellcomparisonoperatorsareusedtovalidatedatapresentwithinyourscripts.Theseoperatorsenableyoutocomparedataandexecutecodebasedonthedata.ThismakesPowerShellanextremelyeffectivetooltouseforprocessingcomplicateddatawiththeavailablecomparisonoperators.

Inthischapter,youwilllearnthefollowingconcepts:

ComparisonoperatorbasicsEqualandnotequalcomparisonoperatorsGreaterthanandlessthancomparisonoperatorsContains,like,andmatchcomparisonoperators-AND/-ORcomparisonoperatorsBestpracticesforcomparisonoperators

ComparisonoperatorbasicsWhenyouareusingcomparisonoperators,youarecreatingexpressionsthatevaluatetoeitherTrueorFalse.Inprogramming,thisisknownasBoolean.Inthesimplestform,youareaskingPowerShelltoevaluatesimilaritiesordissimilaritiesbetweentwoitems.Basedonthefindingsfromthatexpression,itwillreturnTrueorFalse.WhenthewholeexpressionreturnsFalse,PowerShelldoesn’tcontinuetoprocessitemsinthestatement.WhenthewholeexpressionreturnsTrue,PowerShellwillproceedforwardintothestatementandexecutethecodewithinthestatement.

Ofthemanybuilt-invariablesthatPowerShellhas,therearetwobuilt-inBooleanvariables.Thesetwovariablesare$Trueand$False.Whenyoucall$True,itimpliesthatthevalueisBooleanandissettoTrue.Whenyoucall$False,itimpliesthatthevalueisBooleanandissettoFalse.

Ascriptthatshowshowtousebasiccomparisonoperatorswouldlooklikethis:

$TrueVariable=$True$FalseVariable=$Falseif($TrueVariable){Write-Host"StatementisTrue."}if($FalseVariable){Write-Host"StatementisFalse."}

Theoutputofthiscommandisshowninthefollowingscreenshot:

ThisexampledisplayshowtodoabasicBooleancomparison.Youfirststartbydeclaring$TrueVariableandsettingitequaltoTrue.Youthendeclare$FalseVariableandsetittoFalse.Youthencreateanifstatementtoevaluatetheexpression$TrueVariabletoseewhetheritevaluatestoTrue.SincethevariableissettoTrue,itwillevaluatetoTrueandcontinuetoprocesstheremainingitemsinthestatement.PowerShellwillprinttothescreenthemessageStatementisTrue.Youthencreateanotherifstatementtoevaluatetheexpression$FalseVariabletoseewhetheritevaluatestoTrue.AsthevariableissettoFalse,theexpressionwillevaluatetoFalseandstopprocessingthestatement.

EqualandnotequalcomparisonThemostbasicandmostusedcomparisonoperatorisequalto(-eq).Thisoperatorisflexibleinnatureasitcanbeusedforstrings,integers,andobjects.The-eqoperatorisusedbycallingvalue1isequaltovalue2.Whenthe–eqoperatorevaluatesthestatement,itwillreturnaBooleanvalueofeitherTrueorFalse.IftheexpressionevaluatestobeTrue,PowerShellwillcontinuetoproceedtoexecutethecode.

Ascriptthatshowshowtouseequalcomparisonoperatorswouldlooklikethis:

$value1="PowerShell"$value2="PowerShell"if($value1–eq$value2){Write-Host"It'sEqual!"}


Fromtheprecedingexample,youwillseethattheequalcomparisonoperatordeterminesthat$value1isequalto$value2anditwritestothescreenIt'sEqual!.Intheinstancethatyouwanttodeterminewhethertwovaluesarenotequal,youcanusethe–neoperator.Thisdoestheinverseofthe–eqoperator.

Ascriptthatshowshowtousenotequalcomparisonoperatorswouldlooklikethis:

$value1="PowerShell"$value2="POSH"if($value1–ne$value2){Write-Host"ValuesAreNotEqual"}


Whenyouruntheprecedingscript,PowerShellwilldeterminethat$value1and$value2arenotequal.ThescriptwillwritetothescreenthemessageValuesAreNotEqual.Whilescripting,itisimportanttominimizetheuseofthenotequal–neoperator.Whenyoustartlayeringisequaltoandnotequaltoinyourscripts,thelogicalcomplexityofthescriptsignificantlyincreases.Thisiswhyitisrecommendedthatbeginnersshouldtypicallyonlyusethe–neoperatorininstanceswhereavaluecannotequalaspecificvalueandeveryothervalueisacceptable.

Ascriptthatshowshowtouse“notequal”comparisonoperatorswouldlooklikethis:

$value="Thisisavalue."$length=$value.length

If($length–ne0){Write-Host"Thevariablehasdatainit.Dothisaction"}


Theprecedingexampledisplaystheproperuseofthe–neoperatorforbestpractices.Thisscriptcountsthecharactersin$value,andifthelengthofthevariableisnotequalto0,thescriptwillwritetotheconsoleThevariablehasdatainit.Dothisaction.Inyourscripting,youwillwanttofollowsuitwhereyouuse–neforverificationthatthedataisnotvalidbeforecontinuingwithyourscript.

GreaterthanandlessthancomparisonPowerShellhastwooperatorstocomparetwovaluestodeterminewhethertheyaregreaterthan(–gt)orlessthan(-lt)eachother.Thisisnotjustlimitedtonumbers,butalsohastheabilitytocomparedatesandtimesaswell.Thesearehelpfulininstanceswhereyouneedtocomparefilesizesormodificationdatesonfiles.

Ascriptthatshowshowtousethe“lessthan”comparisonoperatorwouldlooklikethis:

$number1=10$number2=20If($number1–lt$number2){Write-Host"Value$number1islessthan$number2"}


Intheprecedingexample,yousetthe$number1variableto10andthe$number2variableto20.Youthenusethe“lessthan”(–lt)operatortodeterminewhetherthe$number1variableislessthan$number2.Sincethisatruestatement,theconsoleoutputsthemessageValue$number1islessthan$number2.

Ascriptthatshowshowtousethe“greaterthan”comparisonoperatorwouldlooklikethis:

$olddate=Get-DateStart-Sleep–seconds2$newdate=Get-DateIf($newdate–gt$olddate){Write-Host"Value$newdateisgreaterthan$olddate"}


Inthisscript,youstartbysettingthe$olddatevariabletothecurrentdateandtime.Thestart-sleepcmdletisthenusedtopausethescriptfor2seconds.Whenthescriptcontinues,youset$newdateandtimevariableto2secondslater.Byusingthegreaterthan(-gt)operator,youdeterminethatthevaluesaredifferentandthatthe$newdatevalueisgreaterthanthe$olddatevalue.

TipInadditionto“greaterthan”and“lessthan”operators,youalsohavetheoptionto

compare“greater”or“equal”(-ge)and“less”or“equal”(-le).Thesecomparisonoperatorscanbehandywhencreatingcountersorloopsthatrequireyoutoincrementanumberuntilitequalsorisgreaterthanaspecificvalue.

Contains,like,andmatchoperatorsThe-contains,-like,and-matchoperatorsareverysimilarinfunction.Whiletheyallcomparedata,theyallhavetheirownpurposeinyourscripts.Eachoftheseoperatorsarecase-insensitive.Thismeansthatwhenyouaresearchingforitemsusingtheseoperators,theywillmatchallinstancesofthevalueintheexpression.Ininstanceswhereyouneedthesearchtobecase-specific,youcanappendcinfrontoftheoperatortoforcecasesensitivity.Thesewouldlooklike–ccontains,-clike,and–cmatch.Toforcecaseinsensitivity,youcanalsoappendiinfrontoftheoperator.Thesewouldlooklike–icontains,-ilike,and–imatch.

Eachoftheseoperatorsalsohasaninverseoperatorthatisformedbyappendingtheword“not”infrontoftheoperator.Examplesoftheseoperatorsinclude–notcontains,-notlike,and-notmatch.Youmayalsoappendcasesensitivityandcaseinsensitivitytotheseoperators.

The-containsoperatorlooksforanexactmatchtoavalueinanexpression.ItwillthenreturnaTrueandFalseresult.The–containsoperatorisflexibleasitcanevaluatetheindividualvaluesinanarraywithasingleexpression.Thisallowsyoutocreateefficiencyinyourcodebyevaluatingmorethanoneitemperlineofcode.

Ascriptthatshowshowtousethe-Containscomparisonoperatorwouldlooklikethis:

$myarray="this","is","my","array"If($myarray–contains"this"){Write-Host"Thearraycontainstheword:this"}If($myarray–notcontains"that"){Write-Host"Thearraydoesnotcontaintheword:that"}


Intheprecedingexample,youcreateanarraywithfourvaluesinit.Youthenusethe–containsoperatortodeterminewhetherthearrayhasthethisvalue.Asthearraydoeshavethisvalue,itthenevaluatesthestatementtobeTrue,andproceedstowritetotheconsolethemessageThearraycontainstheword:this.Thesecondpartofthisevaluationistochecktoseewhether$myarraydoesnotcontainthewordthatbyusingthe–notcontainsoperator.Since$myarraydoesnothavethewordthat,itproceedstowritetotheconsoleThearraydoesnotcontaintheword:that.

The-likecomparisonoperatorisdifferentthanthe-containsoperator.The–likeoperatorrequiresthatbothsidesoftheexpressionshouldbeevaluatedtomatchthefullstring.Youcanquicklydeterminewhethertherearevaluesthatareclosetoavalueyouarelookingfor,whichwillthenreturnTrueorFalse.Thisiswhythe–likecomparison

operatortypicallyuseswildcardcharactersdesignatedbyanasterisk(*)orquestionmark(?).Itprovidestheflexibilitytoquicklysearchavarietyofvaluesusingasingleexpression.Theasteriskwildcarddesignatesthattheexpressioncanmatchanyvaluesbeforeorafterthestatedword,dependingonwheretheasteriskisplaced.Thequestionmarkallowsyoutomatchanyvaluespresentbetweentwostrings.Forexample,youcanuse–like"myfile?.txt",whichwillmatchanyvaluethatstartswithmyfileandendswiththeextension.txt.AnyvaluesbetweenthosecharacterswillbereturnedasTrue.

Ascriptthatshowshowtousethe–likecomparisonoperatorwouldlooklikethis:

$myexample="ThisisaPowerShellexample."If($myexample–like"*shell*"){Write-Host"Thevariablehasawordthatislikeshell"}If($myexample–notlike"*that*"){Write-Host"Thevariabledoesn'thaveawordthatislikethat"}


Theprecedingscriptdisplaysthestring$myexample,forwhichyousearchforthevalueofshell.Asthevalueispartofanotherword,youneedtoappendthewildcardcharacteronbothsidesoftheword“shell”.Whenyousearchfortheword*shell*,includingthewildcardcharacters,theresultreturnstrue.TheconsolethenoutputsthemessageThevariablehasawordthatislikeshell.Whenyouexecutethesecondcomparisonusingthe–notlikeoperator,youareabletosearchthestringforwordsthatarenotlikethat.Sinceyouusethewildcardsoneachsideoftheword,itdoesasecondarycomparisontomakesurethattherearen’tpartialvaluesinthevariablethatreflectthat.Sincetherearenovaluesinthevariablethatevaluatetobelikethat,itoutputstothescreenthemessageThevariabledoesn'thaveawordthatislikeshell.

TipYouhavetouseanasterisk(*)onbothsidesofthesearchevaluationcriteriaasPowerShellinterpretseverycharacterinthesentenceasavalue.Whileinherentlyyoumaybreakaparteachwordinthevariableasseparatevalues,PowerShellseesitasonecontiguousgroupofcharacters.Tofindasubstringofavariableandhaveitevaluateto“True”usingthe–likeoperator,youwillneedtouseanasterisk(*)onbothsides.

Thematchcomparisonoperatorusesregularexpressionstomatchinformationbetweentwovariables.The-matchoperatorisuniqueinthefactthatitautopopulatesavariablenamed$matcheswiththewordthatmatchesyoursearch.Thisishelpfulintheinstancewhereyouneedtoonlyretrieveobjectsthatmatchacertaincriteria.With“match”,youcanalsoleveragetheuseofregularexpressionstomatchcriteriatoavariable.

Ascriptthatshowshowtousethe–matchand-notmatchcomparisonoperatorswouldlooklikethis:

$myexample="Thenetworkwentdown."If($myexample–match"[o]"){Write-Host"Thevariablematchedthelettero.(Containstwoo's)"}$matchesIf($myexample–notmatch"[U]"){Write-Host"ThevariabledoesnotmatchU.(Doesn'thaveaU)"}


Theprecedingexamplecreatesanewvariablenamed$myexamplewiththestringvalueofThenetworkwentdown..Youthencomparethe$myexamplevariabletotheregularexpression[o]oronethatcontainsaninstanceofotoseethatit’samatch.Sinceoexistsatleastoncecontainedin$myexample,theexpressionreturnsTrueandtheconsoleoutputsthemessageThevariablematchedthelettero.(Containstwoo's).Afteryoumakethatcomparison,youthendisplaythecontentsofthe$matchesvariable.Youwillseethatthe$matchvariableautopopulateswiththevalueofanindexof0andnameofo.Thelastpartofthescriptisanevaluationtoseewhether$myexampledoesnotmatchtheregularexpressionof[U]ordoesnotcontainaninstanceofU.SincethevariabledoesnotcontainaninstanceoftheletterU,itevaluatestobeTrueandwritestotheconsolethemessageThevariabledoesnotmatchU.(Doesn'thaveaU).

And/ORcomparisonoperatorsThe–andand–orcomparisonoperatorsareusedtoevaluatemultipleexpressionspresentwithinasinglelineofcode.TheseareusedtoseewhethertwoormoreexpressionsevaluatetobeTrue.The–andcomparisonoperatormandatesthatbothevaluationsmustevaluatetobeTruetoproceedinthestatement.Thismeansthatexpression1andexpression2mustbeTruetocontinue.The–orcomparisonoperatoronlyrequiresoneofthetwoexpressionstobeTrue.Thismeansthatexpression1orexpression2canbeTruetocontinue.AsyouarelearningPowerShell,youwillwanttousecautionwhileusingthe-andand-orcomparisonoperatorsastheycanquicklycomplicatethelogicofyourscripts.

Ascriptthatshowshowtouse–andand-orcomparisonoperatorswouldlooklikethis:

$myvar=$True$myothervar=$FalseIf($myvar–eq$True–AND$myothervar–eq$False){Write-Host"BothstatementsevaluatetobeTrue"}If($myvar–eq$True–OR$myothervar–eq$True){Write-Host"AtleastonestatementevaluatestobeTrue"}


Theprecedingexamplebrieflydisplayshowtousethe–andoperatorandthe–oroperator.Inthisexample,youcreatetwodifferentvariables.Youthenchecktoseewhether$myvarequalsTrue,whichevaluatestobeTrue.Youevaluatewhether$myothervarisequaltoFalse,whichevaluatestobeTrue.Inorderforthe–andoperatortobesuccessful,bothstatementshavetoevaluatetobeTrueintheevaluationcriteria.SinceboththestatementsevaluatetobeTrue,theconsoleoutputsthemessageBothstatementsevaluatetobeTrue.Eventhoughthe$myothervarvariableissettoFalse,theevaluationtoseewhetherthatvariableissettoFalsemakesthatstatementTrue.

Thesecondstatementyouevaluateiswheneither$myvaror$myothervarequalsTruebyusingthe–ORoperator.Likethefirstevaluation,thefirstvariableevaluatestobeTrue.However,thesecondvariableevaluatestobeFalse.Sincethe–oroperatoronlyrequiresoneofthetwostatementstobeTrue,theentirestatementevaluatestobeTrue.TheconsolewilloutputthemessageAtleastonestatementevaluatestobeTrue.

BestpracticesforcomparisonoperatorsPowerShelloffersmanydifferentcomparisonoperatorsforusewithinyourscripts.ItiseasytostartbuildingoverlycomplexscriptsbyoverusingcomparisonoperatorsorbyevaluatingitemsthatyoumaynothavetouseinPowerShellfunctioning.Refertothefollowingguidelinestosticktowhenyouaredevelopingyourscripts.Thesewillhelpyouavoidoveruseofcomparisonoperators:

Assumethescriptisdesignedtoproceed:Whenyouassumeyourscriptisdesignedtoproceedtothenextstep,youcanreducethenumberofcomparisonoperatorsyouuse.IfyouexpectavaluetobeTrue,onlymakeastatementtocatchwhetherthestatementisFalse.Don’tchecktoseewhetherthestatementisTrue,asPowerShellisdesignedtosequentiallyproceedanywaytothenextstep.Avoiddoublenegativestatements:Whenyouaredevelopingyourcode,avoidtheuseofdoublenegativestatements.AvoidcheckingtoseewhetheravaluedoesnotequalFalse.Whatyou’rereallytryingtodoischecktoseewhetherastatementevaluatestobeTrue.Doublenegativescanbeconfusingtoyouandotherdevelopersreadingyourcode.Staypositive(True)whileyou’recoding:Alwaysattempttoavoidtheuseofnotandnegativeevaluationstatements.Whiletherecanbeaplaceforthenotbasedoperators,trytocreatecodethatevaluateswhenstatementsareTrue.Thenotbasedoperatorsgrowsignificantlyincomplexitywhenusedwithregularexpressionsandcanbeconfusingtoyouandotherdevelopersreadingyourcode.

SummaryThischapterexploredthemanymethodswithwhichyoucanusePowerShelloperators.Youstartedbylearningthecomparisonoperatorbasics.Youthenlearnedabouttheequalandnotequalandgreaterthanandlessthancomparisonoperators.Youlearnedthatyoucanusetheseoperatorstocomparenumbers,strings,dates,andtimes.Youthenproceededtoexplorethe-contains,-like,and-matchoperators.Youlearnedthatyoucanaddnottotheseoperatorstocreatetheinverseoftheoperator.Youalsounderstoodthatyoucanaddcforcasesensitivityandiforcaseinsensitivitytothecomparisonoperators.Youalsosawhowtojoinmultipleoperatorsusingthe-and/-oroperators.

Thechapterendsbyprovidingthebestpracticesfortheimplementationofcomparisonoperators.Bytheendofthischapter,youshouldbeproficientinusingcomparisonoperators,knowwhattoavoid,andbewellonyourwaytoevaluatingvariablesandarrays.Inthenextchapter,youwillexplorehowyoucancreatecodethatcanbecalledmultipletimesandleveragecomparisonoperatorswithfunctions,loops,switches,andmethods.

Chapter4.Functions,Switches,andLoopsStructuresWhenyouarescriptinginPowerShell,youwillfindthatalotofyourcodingeffortswillrequirethecodetoberepeatedmultipletimesinthesamescript.Whilerepeatingthesamecodemayhelpyouaccomplishthetask,therearemanyotheroptionsforcodingmoreefficientscripts.Thischapterexploresdifferenttechniquesforwhichyoucanreusecodeinsteadofrepeatingthesamecodesegmentswithinthesamescript.

Inthischapter,youwilllearnaboutthefollowingconcepts:

CreationoffunctionsCreationofloopsCreationofswitchesCombiningtheuseoffunctions,switches,andloopsBestpracticesforfunctions,switches,andloops

FunctionsWhenyouneedtoqueryorexecutecodemorethanonce,thegeneralruleisthatyoushouldcreateafunctiontoperformtheaction.Functionsareblocksofreusablecode,whichyoucanexecutemultipletimesbycallingthefunction’sname.Youmustplaceafunctionnearthebeginningortopofthescript.ThisallowsPowerShelltointerpretthewholefunctionbeforeyouuseitlaterinthecode.Allothercode,includinginvokingthefunctions,shouldfollowthefunctionssection.IfyoucallafunctionthathasnotyetbeenparsedbyPowerShell,itwillthrowanexceptionstatingthatnosuchcmdletorfunctionexists.

Functionnamescanbeanywordorsetofwords;however,itisrecommendedtonamethefunctionsimilartotheverb-nouncmdletnamingsyntax.Tocreateafunction,youneedtousethewordFunctionanddeclareafunctionnamelikedisplay-text.Youthenneedtoenclosetherepeatablecommandsincurlybracketsafterthefunctionname.

Thepropersyntaxofafunctionlookslikethis:

FunctionDisplay-Text{Write-Host"ShowingText"}Display-Text


Thisexampledisplayshowtoproperlydeclareafunction.YoufirstcalltheFunctioncommandwiththeDisplay-Textfunctionname.YouthenplaceWrite-Host"ShowText"inthecurlybracketsafterdeclaringthefunctionname.YouthencallthefunctionbytypingDisplay-Text.Afterexecutingthescript,theconsolewillprinttothescreenthemessageShowingText.

Functionsalsoallowyoutopassindataforprocessing.Oneofthemethodstopassindataintoafunctionistodeclarevariablesafterthefunctionnameinparentheses.Thisfunctionwillthenbeabletousethosevariablesandthedatainthosevariableswithinitself.Ifyouwanttopassinmultipleargumentsintoafunction,youcanseparateeachvariablewithacomma.

Theformattodeclareafunctionwithparametersinparentheseslookslikethis:

FunctionDisplay-Text($variable1,$variable2){Write-Host"FirstFunctionArgument:$variable1"Write-Host"SecondFunctionArgument:$variable2"}Display-Text"Hello""Readers"


Thisexampledisplayshowtoproperlydeclareafunctionwiththeparameterinparentheses.YoufirstcalltheFunctioncommandwiththeDisplay-Textfunctionname.Youthenplacethevariables,$variable1withacommaand$variable2inparentheses,beforethecurlybrackets.Insidethecurlybrackets,youdeclareWrite-Host"FirstFunctionArgument:$variable1"andWrite-Host"SecondFunctionArgument:$variable2".YouthencallthefunctionbytypingDisplay-TextwiththeargumentsofHelloandReaders.Afterexecutingthescript,theconsolewillprinttothescreenFirstFunctionArgument:HelloandSecondFunctionArgument:Readers.

AnothermethodtopassindatatoafunctionisthroughtheuseofaparameterblockofParam.Paramtakesinwhateverdatayoupassintothefunctionandstoresthatdataindeclaredvariables.Ifyouwanttopassinmultipleargumentsintoafunction,youcanseparateeachvariablewithacomma.Whenyouaredeclaringparametersusingthismethod,Paramneedstobethefirstitemdeclaredaftertheopencurlybracketinafunction.

Theformattodeclareafunctionwithparamlookslikethis:

FunctionDisplay-Text{Param($variable1,$variable2)Write-Host"FirstFunctionArgument:$variable1"Write-Host"SecondFunctionArgument:$variable2"}Display-Text"Hello""Readers"


ThisexampledisplayshowtoproperlydeclareafunctionwithparametersinaParamblock.YoufirstcalltheFunctioncommandwiththeDisplay-Textfunctionname.YouthencalltheParamblockasthefirstcommandinsidethecurlybrackets.InsidetheParamblock,youdeclarethevariables$variable1withacommaand$variable2.AftertheParamblock,youdeclareWrite-Host"FirstFunctionArgument:$variable1"andWrite-Host"SecondFunctionArgument:$variable2".YouthencallthefunctionbytypingDisplay-TextwiththeargumentsHelloandReaders.Afterexecutingthescript,theconsolewillprinttothescreenFirstFunctionArgument:HelloandSecondFunctionArgument:Readers.

TheParamblockisspecialasitcanalsoacceptadditionaldecoratorswhendeclaringthevariables.The[Parameter()]decoratorallowsyoutoincludeadditionalargumentsthatenableyoutovalidatevariablesandevenprovidehelpinformationforvariablesinfunctions.WhenyoudeclaretheMandatoryargumentandsetitequalto$True,itwillrequirethatthevariableisusedinthefunctiontocontinue.IfyousettheMandatoryargumentto$False,itwillnotberequiredwhenusingthefunction.YoucanalsocallthePositionargument,whichdeclareswhatpositionthevariablewillbedeclared.ThismeansthatifyousetthePositionargumentto1,itmustbethefirstargumentpassedintothefunction.Ifyoudon’tusethePositionargument,youwillonlybeabletopassinthevariablesusingparameterthatreferencesthevariablename.AnotherpopularargumentistheHelpMessageargument,

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