book

Learning Perl, 6th Edition

by Randal L. Schwartz, brian d foy, Tom Phoenix

June 2011

Beginner

386 pages

11h 33m

English

O'Reilly Media, Inc.

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Typographical ConventionsCode ExamplesSafari® Books OnlineHow to Contact UsHistory of This BookChanges from the Previous EditionAcknowledgmentsFrom RandalFrom TomFrom brianFrom All of Us
Questions and AnswersIs This the Right Book for You?Why Are There So Many Footnotes?What About the Exercises and Their Answers?What Do Those Numbers Mean at the Start of the Exercise?What If I’m a Perl Course Instructor?What Does “Perl” Stand For?Why Did Larry Create Perl?Why Didn’t Larry Just Use Some Other Language?Is Perl Easy or Hard?How Did Perl Get to Be So Popular?What’s Happening with Perl Now?What’s Perl Really Good For?What Is Perl Not Good For?How Can I Get Perl?What Is CPAN?How Can I Get Support for Perl?Are There Any Other Kinds of Support?What If I Find a Bug in Perl?How Do I Make a Perl Program?A Simple ProgramWhat’s Inside That Program?How Do I Compile My Perl Program?A Whirlwind Tour of PerlExercises
NumbersAll Numbers Have the Same Format InternallyFloating-Point LiteralsInteger LiteralsNondecimal Integer LiteralsNumeric OperatorsStringsSingle-Quoted String LiteralsDouble-Quoted String LiteralsString OperatorsAutomatic Conversion Between Numbers and StringsPerl’s Built-in WarningsScalar VariablesChoosing Good Variable NamesScalar AssignmentBinary Assignment OperatorsOutput with printInterpolation of Scalar Variables into StringsCreating Characters by Code PointOperator Precedence and AssociativityComparison OperatorsThe if Control StructureBoolean ValuesGetting User InputThe chomp OperatorThe while Control StructureThe undef ValueThe defined FunctionExercises
Accessing Elements of an ArraySpecial Array IndicesList LiteralsThe qw ShortcutList AssignmentThe pop and push OperatorsThe shift and unshift OperatorsThe splice OperatorInterpolating Arrays into StringsThe foreach Control StructurePerl’s Favorite Default: $_The reverse OperatorThe sort OperatorThe each OperatorScalar and List ContextUsing List-Producing Expressions in Scalar ContextUsing Scalar-Producing Expressions in List ContextForcing Scalar Context<STDIN> in List ContextExercises
Defining a SubroutineInvoking a SubroutineReturn ValuesArgumentsPrivate Variables in SubroutinesVariable-Length Parameter ListsA Better &max RoutineEmpty Parameter ListsNotes on Lexical (my) VariablesThe use strict PragmaThe return OperatorOmitting the AmpersandNon-Scalar Return ValuesPersistent, Private VariablesExercises
Input from Standard InputInput from the Diamond OperatorThe Invocation ArgumentsOutput to Standard OutputFormatted Output with printfArrays and printfFilehandlesOpening a FilehandleBinmoding FilehandlesBad FilehandlesClosing a FilehandleFatal Errors with dieWarning Messages with warnAutomatically die-ingUsing FilehandlesChanging the Default Output FilehandleReopening a Standard FilehandleOutput with sayFilehandles in a ScalarExercises
What Is a Hash?Why Use a Hash?Hash Element AccessThe Hash As a WholeHash AssignmentThe Big ArrowHash FunctionsThe keys and values FunctionsThe each FunctionTypical Use of a HashThe exists FunctionThe delete FunctionHash Element InterpolationThe %ENV hashExercises
What Are Regular Expressions?Using Simple PatternsUnicode PropertiesAbout MetacharactersSimple QuantifiersGrouping in PatternsAlternativesCharacter ClassesCharacter Class ShortcutsNegating the ShortcutsExercises
Matches with m//Match ModifiersCase-Insensitive Matching with /iMatching Any Character with /sAdding Whitespace with /xCombining Option ModifiersChoosing a Character InterpretationOther OptionsAnchorsWord AnchorsThe Binding Operator =~Interpolating into PatternsThe Match VariablesThe Persistence of CapturesNoncapturing ParenthesesNamed CapturesThe Automatic Match VariablesGeneral QuantifiersPrecedenceExamples of PrecedenceAnd There’s MoreA Pattern Test ProgramExercises
Substitutions with s///Global Replacements with /gDifferent DelimitersSubstitution ModifiersThe Binding OperatorNondestructive SubstitutionsCase ShiftingThe split OperatorThe join Functionm// in List ContextMore Powerful Regular ExpressionsNongreedy QuantifiersMatching Multiple-Line TextUpdating Many FilesIn-Place Editing from the Command LineExercises

The unless Control StructureThe else Clause with unlessThe until Control StructureExpression ModifiersThe Naked Block Control StructureThe elsif ClauseAutoincrement and AutodecrementThe Value of AutoincrementThe for Control StructureThe Secret Connection Between foreach and forLoop ControlsThe last OperatorThe next OperatorThe redo OperatorLabeled BlocksThe Conditional Operator ?:Logical OperatorsThe Value of a Short Circuit OperatorThe defined-or OperatorControl Structures Using Partial-Evaluation OperatorsExercises
Finding ModulesInstalling ModulesUsing Your Own DirectoriesUsing Simple ModulesThe File::Basename ModuleUsing Only Some Functions from a ModuleThe File::Spec ModulePath::ClassCGI.pmDatabases and DBIDates and TimesExercises
File Test OperatorsTesting Several Attributes of the Same FileStacked File Test OperatorsThe stat and lstat FunctionsThe localtime FunctionBitwise OperatorsUsing BitstringsExercises
Moving Around the Directory TreeGlobbingAn Alternate Syntax for GlobbingDirectory HandlesRecursive Directory ListingManipulating Files and DirectoriesRemoving FilesRenaming FilesLinks and FilesMaking and Removing DirectoriesModifying PermissionsChanging OwnershipChanging TimestampsExercises
Finding a Substring with indexManipulating a Substring with substrFormatting Data with sprintfUsing sprintf with “Money Numbers”Interpreting Non-Decimal NumeralsAdvanced SortingSorting a Hash by ValueSorting by Multiple KeysExercises
The Smart Match OperatorSmart Match PrecedenceThe given StatementDumb MatchingUsing when with Many ItemsExercises
The system FunctionAvoiding the ShellThe Environment VariablesThe exec FunctionUsing Backquotes to Capture OutputUsing Backquotes in a List ContextExternal Processes with IPC::System::SimpleProcesses as FilehandlesGetting Down and Dirty with ForkSending and Receiving SignalsExercises
SlicesArray SliceHash SliceTrapping ErrorsUsing evalMore Advanced Error HandlingautodiePicking Items from a List with grepTransforming Items from a List with mapFancier List UtilitiesExercises
Answers to Chapter 1 ExercisesAnswers to Chapter 2 ExercisesAnswers to Chapter 3 ExercisesAnswers to Chapter 4 ExercisesAnswers to Chapter 5 ExercisesAnswers to Chapter 6 ExercisesAnswers to Chapter 7 ExercisesAnswers to Chapter 8 ExercisesAnswers to Chapter 9 ExercisesAnswers to Chapter 10 ExercisesAnswer to Chapter 11 ExercisesAnswers to Chapter 12 ExercisesAnswers to Chapter 13 ExercisesAnswers to Chapter 14 ExercisesAnswers to Chapter 15 ExercisesAnswers to Chapter 16 ExercisesAnswer to Chapter 17 Exercises
Further DocumentationRegular ExpressionsPackagesExtending Perl’s FunctionalityLibrariesWriting Your Own ModulesDatabasesDirect System Database AccessFlat-File Database AccessOther Operators and FunctionsTransliteration with tr///Here DocumentsMathematicsAdvanced Math FunctionsImaginary and Complex NumbersLarge and High-Precision NumbersLists and Arraysmap and grepBits and PiecesFormatsNetworking and IPCSystem V IPCSocketsSecurityDebuggingCommand-Line OptionsBuilt-in VariablesSyntax ExtensionsReferencesComplex Data StructuresObject-Oriented ProgrammingAnonymous Subroutines and ClosuresTied VariablesOperator OverloadingDynamic LoadingEmbeddingConverting Other Languages to PerlConverting find Command Lines to PerlCommand-Line Options in Your ProgramsEmbedded DocumentationMore Ways to Open FilehandlesThreads and ForkingGraphical User Interfaces (GUIs)And More…
UnicodeUTF-8 and FriendsGetting Everyone to AgreeFancy CharactersFancier CharactersDealing with Unicode in PerlUsing Unicode in Your SourceFancier Characters by NameReading from STDIN or Writing to STDOUT or STDERRReading from and Writing to FilesDealing with Command-Line ArgumentsDealing with DatabasesFurther Reading

Content preview from Learning Perl, 6th Edition

Colophon

The animal on the cover of Learning Perl, Sixth Edition, is a llama (Lama glama), a relation of the camel, and native to the Andean range. Also included in this llamoid group is the domestic alpaca and their wild ancestors, the guanaco and the vicuña. Bones found in ancient human settlements suggest that domestication of the alpaca and the llama dates back about 4,500 years. In 1531, when Spanish conquistadors overran the Inca Empire in the high Andes, they found both animals present in great numbers. These llamas are suited for high mountain life; their hemoglobin can take in more oxygen than that of other mammals.

Llamas can weigh up to 300 pounds and are mostly used as beasts of burden. A pack train may contain several hundred animals and can travel up to 20 miles per day. Llamas will carry loads up to 50 pounds, but have a tendency to be short-tempered and resort to spitting and biting to demonstrate displeasure. To other people of the Andes, llamas also provide meat, wool for clothing, hides for leather, and fat for candles. Their wool can also be braided into ropes and rugs, and their dried dung is used for fuel.

The cover image is a 19th-century engraving from the Dover Pictorial Archive. The cover font is Adobe ITC Garamond. The text font is Linotype Birka; the heading font is Adobe Myriad Condensed; and the code font is LucasFont’s TheSans Mono Condensed.