Effective_awk_Programming_4th_Edition.pdf

GAWK:EffectiveAWKProgramming aUser'sGuidelorgnuawk Edition4.1 April,2014 Arnoldd.robbins Toboldlygowherenomanhasgonebefore"isaRegisteredTrademarkofParamount PicturesCorporatiOn Publishedby FreeSoftwareFoundation 51Franklinstreet.FifthFloor Boston.Ma02110-1301USA Phone:+1-617-542-5942 Fax:+1-617-5422652 Email:gnu@gnu.org Url:http://www.gnu.org ISBN1882114280 Copyright1989,1991,1992,1993,1996-2005,2007,20092014 FreeSoftwareFoundation.Inc ThisisEdition4.1ofGAWK:EffectiveAWKProgramming:AUser'sGuideforGNUAwk forthe1.1.1(orlater)versionoftheGNUimplementationofAWK Permissionisgrantedtocopy,distributeandormodifythisdocumentunderthetermsof theGNUFreeDocumentationLicense,Version1.3oranylaterversionpublishedbythe FrccSoftwarcfoundationwiththcinvariantscctionsbcing"GNGcncralpublicliccnsc theFront-Covertextsbeing(a)(seebelow),andwiththeBack-CoverTextsbeing(b)(see belowAcopyofthelicenseisincludedinthesectionentitled"GNUFreeDocumentation License a.“AGNUManual b."YouhavethefreedomtocopyandmodifythisgNU manua Buyingcopiesfromthe FSFsupportsitindevelopinggnuandpromotingsoftwarefreedom ToMiriaTm,Jormakingmecomplele ToChana,forthejoyyoubringus ToRivka,fortheexponentialincrease ToNachum,fortheaddeddimension ToMalka,forthenewbeginning Shortcontents Foreword Preface PartI:Theawklanguage 1GettingStartedwithawk ....13 2Runningawkandgawk 27 3RegularExpressions 41 4ReadinginputFile ...53 5PrintingOutput 81 6Expressions.......... 7 7Patterns.ActionsandVariables .119 8Arraysinawk 145 9Functions ...,.,..,,..159 Partll:ProblemSolvingWithawk 10ALibraryofawkFunctions .....20 11Practicalawkprograms 233 PartIII:MovingBeyondStandardawkWithgawk 12AdvancedFeaturesofgawk 279 13Internationalizationwithgawk 293 4DebuggingawkPrograms ...,,,303 15ArithmeticandArbitraryPrecisionArithmeticwithgawk..319 16WritingExtensionsforgawk 335 PartIV:Appendices aTheEvolutionoftheawklanguage 391 bInstallinggawk .407 CImplementationNotes ,425 DBasicProgramming:Concepts 435 ossary 439 GNUGeneralPubliclicense .......449 GNUFreedocumentationlicense 461 Index 469 TableofContents Foreword Preface ·鲁 3 Historyofawkandgawk 4 arosebyanyotherName 4 UsingthisBook 0 TypographicalConventions 7 Darkcorners 7 ThegnUProjectandThisBook 9 Acknowledgments Partl:Theawklanguage GettingStartedwithawk 13 1.1Howtorunawkprograms .13 1.1.1One-ShotThrowawayawkPrograms 13 1.1.2RunningawkWithoutInputFiles 14 1.1.3RunningLongprograms 14 1.1.4Executableawkpros gram 15 1.1.5Commentsinawkprograms ,,,,16 1.1.6Shell-QuotingIssues 17 1.1.6.1QuotinginMS-WindowsBatchFiles 1.2DataFilesfortheexample 18 1.3SomeSimpleexamples 19 1.4AnExamplewithTwoRules ,21 1.5AMoreComplexexample 22 1.6awkStatementsVersusLines 23 1.7OtherFeaturesofawk 24 1.8Wh Useawk 24 2Runningawkandgawk ·.···· ....27 2.1Invokingawk 27 2.2Command-LineOptions ….27 2.3OtherCommand-LineArguments 33 2.4NamingStandardInput 34 2.5TheEnvironmentVariablesgawkUses 34 2.5.1TheAWKPATHEnvironmentVariable...........34 2.5.2TheAWKLATHEnvironmentvariable 2.5.3OtherEnvironmentVariables 35 2.6gawksExitStatus 37 2.7IncludingOtherFilesIntoYourProgram 37 ivGAWK:EffectiveAWKProgramming 2.8LoadingSharedLibrariesIntoYourProgram .38 29ObsoleteOptionsand/orfeatures……………39 2.10UndocumentedOptionsandFeatures ∴,.39 3RegularExpressions 3.1HowtoUscRegularExpressions 41 3.2Escapesequences 42 3.3RegularExprcssionOpcrators 44 3.4USingBracketExpressions 47 3.5gawk ficRegexpOperators 48 3.6CaseSensitivityinMatching ..49 3.7HowMuchTextMatches? 50 3.8UsingDynamicRegexps 51 4ReadingInputFiles 53 4.1HowInputIssplitintoRecords 53 1.2ExaminingFields 56 4.3Nonconstantfieldnumbers 57 4.4ChangingtheContentsofaField...............58 4.5SpecifyingHowFieldsAl 60 4.5.1WhitespaceNormallySeparatesFiclds 61 4.5.2USingRegularExpressionstoSeparateFields 61 4.5.3MakingEachCharacteraSeparateField 鲁鲁春 63 4.5.4SettingFSfromtheCommandline 63 4.5.5MakingTheFullLineBeaSingleField 64 4.5.6Field-SplittingSummary 64 4.6ReadingFixed-WidthData 66 4.7DefiningFieldsByContent 67 4.8Multiple-LineRecords 69 4.9ExplicitInputwithgetline 71 4.9.1UsinggetlinewithNoArguments 72 4.9.2USinggetlineintoavariable ..72 4.9.3U: ethinefromafile 73 4.9.4UsinggetlineintoaVariablefromaFile∴……73 4.9.5USinggetline[roInaPipe 74 4.9.6UsinggetlineintoaVariablefromaPipe 75 4.9.7UsinggetlineIronaCoprocess 4.9.8UsinggetlineintoaVariablefromaCoprocess.....76 4.9.9PointstoRememberAboutgetline 76 4.9.10SummaryofgetlineVariants 77 4.10ReadingInputWithATimeout 77 4.11DircctoricsOnThcCommandLinc..............79