book

Perl by Example, Fourth Edition

Name: Perl by Example, Fourth Edition
Author: Ellie Quigley
ISBN: 9780132381826

by Ellie Quigley

November 2007

Intermediate to advanced

1008 pages

20h 15m

English

Pearson

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Copyright
Praise for Ellie Quigley’s Books
Preface
Acknowledgments
1. The Practical Extraction and Report Language
1.1. What Is Perl?1.2. What Is an Interpreted Language?1.3. Who Uses Perl?1.3.1. Which Perl?1.3.2. What Is Perl 6?1.4. Where to Get Perl1.4.1. What Version Do I Have?1.5. What Is CPAN?1.6. Perl Documentation1.6.1. Perl Man Pages1.6.2. HTML Documentation1.7. What You Should Know1.8. What’s Next?
2. Perl Quick Start
2.1. Quick Start, Quick Reference2.1.1. A Note to Programmers2.1.2. A Note to Non-Programmers2.1.3. Perl Syntax and ConstructsRegular ExpressionsPassing Arguments at the Command LineReferences, PointersObjectsCreating a ClassInstantiating a ClassLibraries and ModulesPath to LibrariesTo include a FileDiagnostics2.2. Chapter Summary2.3. What’s Next?
3. Perl Scripts
3.1. Script Setup3.2. The Script3.2.1. StartupUNIX/Mac OSWindows3.2.2. Finding a Text Editor3.2.3. Naming Perl Scripts3.2.4. Statements, Whitespace, and Linebreaks3.2.5. Comments3.2.6. Perl Statements3.2.7. Using Perl Built-in Functions3.2.8. Executing the Script3.2.9. Sample Script3.2.10. What Kinds of Errors to Expect3.3. Perl at the Command Line3.3.1. The -e Switch3.3.2. The -n SwitchReading from a FileReading from a Pipe3.3.3. The -c Switch3.4. What You Should Know3.5. What’s Next?
4. Getting a Handle on Printing
4.1. The Filehandle4.2. Words4.3. The print Function4.3.1. QuotesBreaking the Quoting Rules4.3.2. Literals (Constants)Numeric LiteralsString LiteralsSpecial Literals4.3.3. Printing LiteralsPrinting Numeric LiteralsPrinting String LiteralsPrinting Special Literals4.3.4. The warnings Pragma and the -w Switch4.3.5. The diagnostics Pragma4.3.6. The strict Pragma and Words4.4. The printf Function4.4.1. The sprintf Function4.4.2. Printing without Quotes—The here documentHere Documents and CGI4.5. What You Should Know4.6. What’s Next?
5. What’s in a Name
5.1. About Perl Variables5.1.1. Types5.1.2. Scope and the Package5.1.3. Naming Conventions5.1.4. Assignment Statements5.1.5. Quoting RulesDouble QuotesSingle QuotesBackquotesPerl’s Alternative Quotes5.2. Scalars, Arrays, and Hashes5.2.1. Scalar VariablesAssignmentCurly BracesThe defined FunctionThe undef FunctionThe $_ Scalar Variable5.2.2. ArraysAssignmentSpecial Scalars and Array AssignmentThe Range Operator and Array AssignmentAccessing ElementsArray SlicesMultidimensional Arrays—Lists of Lists5.2.3. HashesAssignmentAccessing ElementsHash Slices5.2.4. Complex Data StructuresHashes of HashesArray of Hashes5.3. Reading from STDIN5.3.1. Assigning Input to a Scalar Variable5.3.2. The chop and chomp Functions5.3.3. The read Function5.3.4. The getc Function5.3.5. Assigning Input to an Array5.3.6. Assigning Input to a Hash5.4. Array Functions5.4.1. The chop and chomp Functions (with Lists)5.4.2. The exists Function5.4.3. The delete Function5.4.4. The grep Function5.4.5. The join Function5.4.6. The map Function5.4.7. The pack and unpack Functions5.4.8. The pop Function5.4.9. The push Function5.4.10. The shift Function5.4.11. The splice Function5.4.12. The split Function5.4.13. The sort FunctionASCII and Numeric Sort Using SubroutineUsing an Inline Function to Sort a Numeric List5.4.14. The reverse Function5.4.15. The unshift Function5.5. Hash (Associative Array) Functions5.5.1. The keys Function5.5.2. The values Function5.5.3. The each Function5.5.4. Sorting a HashSort Hash by Keys in Ascending OrderSort Hash by Keys in Reverse OrderSort Hash by Keys NumericallyNumerically Sort a Hash by Values in Ascending OrderNumerically Sort a Hash by Values in Descending Order5.5.5. The delete Function5.5.6. The exists Function5.6. More Hashes5.6.1. Loading a Hash from a File5.6.2. Special HashesThe %ENV HashThe %SIG HashThe %INC Hash5.6.3. Context5.7. What You Should Know5.8. What’s Next?
6. Where’s the Operator?
6.1. About Perl Operators6.2. Mixing Data Types6.3. Precedence and Associativity6.3.1. Assignment Operators6.3.2. Relational OperatorsNumericString6.3.3. Equality OperatorsNumericString6.3.4. Logical Operators (Short-Circuit Operators)6.3.5. Logical Word Operators6.3.6. Arithmetic Operators6.3.7. Autoincrement and Autodecrement Operators6.3.8. Bitwise Logical OperatorsA Little Bit about BitsBitwise Operators6.3.9. Conditional Operators6.3.10. Range Operator6.3.11. Special String Operators and Functions6.3.12. Arithmetic FunctionsGenerating Random NumbersThe rand/srand Functions6.4. What You Should Know6.5. What’s Next?

7. If Only, Unconditionally, Forever
7.1. Control Structures, Blocks, and Compound Statements7.1.1. Decision Making—Conditional Constructsif and unless StatementsThe if ConstructThe if/else ConstructThe if/elsif/else ConstructThe unless Construct7.2. Repetition with Loops7.2.1. The while Loop7.2.2. The until LoopThe do/while and do/until Loops7.2.3. The for Loop7.2.4. The foreach Loop7.2.5. Loop ControlLabelsA Labeled Block without a LoopNested Loops and LabelsThe continue Block7.2.6. The switch StatementThe Switch.pm Module7.3. What You Should Know7.4. What’s Next?
8. Regular Expressions—Pattern Matching
8.1. What Is a Regular Expression?8.2. Expression Modifiers and Simple Statements8.2.1. Conditional ModifiersThe if Modifier8.2.2. The DATA FilehandleThe unless Modifier8.2.3. Looping ModifiersThe while ModifierThe until ModifierThe foreach Modifier8.3. Regular Expression Operators8.3.1. The m Operator and MatchingThe g Modifier—Global MatchThe i Modifier—Case InsensitivitySpecial Scalars for Saving PatternsThe x Modifier—The Expressive Modifier8.3.2. The s Operator and SubstitutionChanging the Substitution DelimitersThe g Modifier—Global SubstitutionThe i Modifier—Case InsensitivityThe e Modifier—Evaluating an Expression8.3.3. Pattern Binding Operators8.4. What You Should Know8.5. What’s Next?
9. Getting Control—Regular Expression Metacharacters
9.1. Regular Expression Metacharacters9.1.1. Metacharacters for Single CharactersThe Dot MetacharacterThe s Modifier—The Dot Metacharacter and the NewlineThe Character ClassThe POSIX Character Class9.1.2. Whitespace Metacharacters9.1.3. Metacharacters to Repeat Pattern MatchesThe Greed FactorMetacharacters that Turn off GreedinessAnchoring MetacharactersThe m ModifierAlternationGrouping or ClusteringRemembering or CapturingTurning Off CapturingMetacharacters that Look Ahead and Behind9.1.4. The tr or y FunctionThe tr Delete OptionThe tr Complement OptionThe tr Squeeze Option9.2. Unicode9.2.1. Perl and Unicode9.3. What You Should Know9.4. What’s Next?
10. Getting a Handle on Files
10.1. The User-Defined Filehandle10.1.1. Opening Files—The open Function10.1.2. Open for ReadingClosing the FilehandleThe die FunctionReading from the Filehandle10.1.3. Open for Writing10.1.4. Win32 Binary Files10.1.5. Open for Appending10.1.6. The select Function10.1.7. File Locking with flock10.1.8. The seek and tell FunctionsThe seek FunctionThe tell Function10.1.9. Open for Reading and Writing10.1.10. Open for PipesThe Output FilterSending the Output of a Filter to a FileInput Filter10.2. Passing Arguments10.2.1. The ARGV Array10.2.2. ARGV and the Null Filehandle10.2.3. The eof Function10.2.4. The -i Switch—Editing Files in Place10.3. File Testing10.4. What You Should Know10.5. What’s Next?
11. How Do Subroutines Function?
11.1. Subroutines/Functions11.1.1. Defining and Calling a SubroutineA Null Parameter ListForward ReferenceScope of Variables11.2. Passing ArgumentsCall-by-Reference and the @_ ArrayCall-by-Value with local and myThe local FunctionThe my OperatorUsing the strict Pragma (my and our)11.2.1. Prototypes11.2.2. Return Value11.2.3. Context and SubroutinesThe wantarray Function and User-Defined Subroutines11.3. Call-by-Reference11.3.1. Symbolic References—TypeglobsDefinitionPassing by Reference with AliasesMaking Aliases Private—local versus myPassing Filehandles by ReferenceSelective Aliasing and the Backslash Operator11.3.2. Hard References—PointersDefinitionDereferencing the PointerPointers as ArgumentsPassing Pointers to a Subroutine11.3.3. Autoloading11.3.4. BEGIN and END Subroutines (Startup and Finish)11.3.5. The subs Function11.4. What You Should Know11.5. What’s Next?
12. Modularize It, Package It, and Send It to the Library!
12.1. Packages and Modules12.1.1. Before Getting Started12.1.2. An Analogy12.1.3. Definition12.1.4. The Symbol Table12.2. The Standard Perl Library12.2.1. The @INC ArraySetting the PERL5LIB Environment Variable12.2.2. Packages and .pl FilesThe require FunctionIncluding Standard Library RoutinesUsing Perl to Include Your Own Library12.2.3. Modules and .pm FilesThe use Function (Modules and Pragmas)12.2.4. Exporting and ImportingThe Exporter ModuleUsing perldoc to Get Documentation for a Perl ModuleUsing a Perl 5 Module from the Standard Perl Library12.2.5. How to “use” a Module from the Standard Perl Library12.2.6. Using Perl to Create Your Own Module12.3. Modules from CPANThe Cpan.pm Module12.3.1. Using PPMCreating Extensions and Modules for CPAN with the h2xs Tool12.4. What You Should Know12.5. What’s Next?
13. Does This Job Require a Reference?
13.1. What Is a Reference? What Is a Pointer?13.1.1. Symbolic versus Hard ReferencesThe strict Pragma13.1.2. Hard References, PointersThe Backslash OperatorDereferencing the Pointer13.1.3. References and Anonymous VariablesAnonymous ArraysAnonymous Hashes13.1.4. Nested Data StructuresLists of ListsArray of HashesHash of HashesHash of Hashes with Lists of Values13.1.5. References and SubroutinesAnonymous SubroutinesSubroutines and Passing by Reference13.1.6. Filehandle References13.1.7. The ref Function13.2. What You Should Know13.3. What’s Next?
14. Bless Those Things! (Object-Oriented Perl)
14.1. The OOP Paradigm14.1.1. Packages and Modules Revisited14.1.2. Some Object-Oriented Lingo14.2. Classes, Objects, and Methods14.2.1. Real World14.2.2. The Steps14.2.3. Classes and Privacy14.2.4. ObjectsThe House Class14.2.5. The bless Function14.2.6. MethodsDefinitionTypes of MethodsInvoking MethodsClass Method InvocationInstance Method Invocation14.2.7. What an Object-Oriented Module Looks LikeThe Class Constructor MethodThe Class and Instance MethodsPassing Parameters to Constructor MethodsPassing Parameters to Instance MethodsNamed ParametersThe user/driver ProgramThe Object-Oriented Module14.2.8. Polymorphism and Dynamic BindingThe :: versus –> Notation14.2.9. Destructors and Garbage Collection14.3. Anonymous Subroutines, Closures, and Privacy14.3.1. What Is a Closure?14.3.2. Closures and ObjectsUser of the Module14.4. Inheritance14.4.1. The @ISA Array and Calling Methods14.4.2. $AUTOLOAD, sub AUTOLOAD, and UNIVERSAL14.4.3. Derived Classes14.4.4. Multiple Inheritance14.4.5. Overriding a Parent Method14.5. Public User Interface—Documenting Classes14.5.1. pod Files14.5.2. pod Commands14.5.3. How to Use the pod Interpreters14.5.4. Translating pod Documentation into Text14.5.5. Translating pod Documentation into HTML14.6. Using Objects from the Perl Library14.6.1. Another Look at the Standard Perl Library14.6.2. An Object-Oriented Module from the Standard Perl Library14.6.3. Using a Module with Objects from the Standard Perl Library14.7. What You Should Know14.8. What’s Next?
15. Those Magic Ties and DBM Stuff
15.1. Tying Variables to a Class15.1.1. The tie Function15.1.2. Predefined Methods15.1.3. Tying a Scalar15.1.4. Tying an Array15.1.5. Tying a Hash15.2. DBM Files15.2.1. Creating and Assigning Data to a DBM File15.2.2. Retrieving Data from a DBM File15.2.3. Deleting Entries from a DBM File15.3. What You Should Know15.4. What’s Next?
16. CGI and Perl: The Hyper Dynamic Duo
16.1. Static and Dynamic Web Pages16.2. How It all Works16.2.1. Internet Communication between Client and ServerThe HTTP ServerHTTP Status Codes and the Access Log FileThe URL (Uniform Resource Locator)File URLs and the Server’s Root Directory16.3. Creating a Web Page with HTMLCreating TagsA Simple HTML Document16.4. How HTML and CGI Work Together16.4.1. A Simple CGI ScriptThe HTTP Headers16.4.2. Error Log FilesError Logs and STDERR16.5. Getting Information Into and Out of the CGI Script16.5.1. CGI Environment VariablesAn HTML File with a Link to a CGI Script16.6. CGI and Forms16.6.1. Input Types for Forms16.6.2. Creating an HTML FormA Simple Form with Text Fields, Radio Buttons, Check Boxes, and Pop-up Menus16.6.3. The GET MethodThe CGI Script16.6.4. Processing the Encoded DataThe Encoded Query StringDecoding the Query String with PerlParsing the Form’s Input with PerlDecoding the Query String16.6.5. Putting It All TogetherThe GET Method16.6.6. The POST Method16.6.7. Handling E-mailThe SMTP Server16.7. The CGI.pm Module16.7.1. Introduction16.7.2. Advantages16.7.3. Two Styles of Programming with CGI.pmThe Object-Oriented StyleFunction-Oriented Style16.7.4. An Important Warning!16.7.5. HTML Form MethodsCreating the HTML Form16.7.6. How CGI.pm Works with FormsThe start_html MethodThe start_form MethodThe submit MethodThe param MethodChecking the Form at the Command Line16.7.7. CGI.pm Form Elements16.7.8. Methods Defined for Generating Form Input FieldsThe textfield() MethodThe checkbox() MethodThe radio_group() and popup_menu() MethodsLabelsThe popup_menu() MethodThe submit() and reset() MethodsClearing FieldsThe override ArgumentThe defaults Method16.7.9. Error HandlingThe carpout and fatalsToBrowser MethodsChanging the Default Message16.7.10. HTTP Header Methods
17. Perl Meets MySQL—A Perfect Connection
17.1. Introduction17.2. What Is a Relational Database?17.2.1. Client/Server Databases17.2.2. Components of a Relational DatabaseThe Database ServerThe DatabaseTablesRecords and FieldsColumns/FieldsRows/RecordsPrimary Key and IndexesThe Database Schema17.2.3. Talking to the Database with SQL (the Structured Query Language)English-like GrammarSemicolons Terminate SQL StatementsNaming ConventionsReserved WordsCase SensitivityThe Result Set17.3. Getting Started with MySQL17.3.1. Why MySQL?17.3.2. Installing MySQL17.3.3. Connecting to MySQLEditing Keys at the MySQL ConsoleSetting a Password17.3.4. Graphical User ToolsThe MySQL Query BrowserThe phpMyAdmin ToolThe MySQL Privilege System17.3.5. Finding the DatabasesCreating and Dropping a Database17.3.6. Getting Started with Basic CommandsCreating a Database with MySQLSelecting a Database with MySQLCreating a Table in the DatabaseData TypesAdding Another Table with a Primary KeyInserting Data into TablesSelecting Data from Tables—The SELECT CommandSelecting by ColumnsSelect All ColumnsThe WHERE ClauseSorting TablesJoining TablesDeleting RowsUpdating Data in a TableAltering a TableAdd a ColumnDrop a ColumnAdd a Primary KeyDropping a TableDropping a Database17.4. What Is the Perl DBI?17.4.1. Installing the DBIDBI-MySQL with PPMPPM QuickstartSteps to Install with PPMThe PPM GUIUsing PPM with LinuxInstalling DBI Using CPAN17.4.2. The DBI Class Methods17.4.3. How to Use DBI17.4.4. Connecting to and Disconnecting from the DatabaseThe connect() Method17.4.5. The disconnect() Method17.4.6. Preparing a Statement Handle and Fetching ResultsSelect, Execute, and Dump the ResultsSelect, Execute, and Fetch a Row as an ArraySelect, Execute, and Fetch a Row as a Hash17.4.7. Handling Quotes17.4.8. Getting Error MessagesAutomatic Error HandlingThe PrintError AttributeThe RaiseError AttributeManual Error HandlingError Diagnostic MethodsError Diagnostic VariablesExamples of Error MesssagesBinding Columns and Fetching ValuesBinding ColumnsThe ? PlaceholderUsing a PlaceholderUsing Multiple PlaceholdersUsing Placeholders to Insert Multiple RecordsBinding Parameters and the bind_param() MethodCached Queries17.5. Statements that Don’t Return Anything17.5.1. The do() methodAdding EntriesDeleting EntriesUpdating Entries17.6. TransactionsCommit and Rollback17.7. Using CGI and the DBI to Select and Display Entries17.8. What’s Left?17.9. What You Should Know17.10. What’s Next?
18. Interfacing with the System
18.1. System Calls18.1.1. Directories and FilesBackslash IssuesThe File::Spec Module18.1.2. Directory and File AttributesUNIXWindows18.1.3. Finding Directories and Files18.1.4. Creating a Directory—The mkdir FunctionUNIXWindows18.1.5. Removing a Directory—The rmdir Function18.1.6. Changing Directories—The chdir Function18.1.7. Accessing a Directory via the Directory FilehandleThe opendir FunctionThe readdir FunctionThe closedir FunctionThe telldir FunctionThe rewinddir FunctionThe seekdir Function18.1.8. Permissions and OwnershipUNIXWindowsThe chmod Function (UNIX)The chmod Function (Windows)The chown Function (UNIX)The umask Function (UNIX)18.1.9. Hard and Soft LinksUNIXWindowsThe link and unlink Functions (UNIX)The symlink and readlink Functions (UNIX)18.1.10. Renaming FilesThe rename Function (UNIX and Windows)18.1.11. Changing Access and Modification TimesThe utime Function18.1.12. File StatisticsThe stat and lstat Functions18.1.13. Low-Level File I/OThe read Function (fread)The sysread and syswrite FunctionsThe seek FunctionThe tell Function18.1.14. Packing and Unpacking Data18.2. Processes18.2.1. UNIX Processes18.2.2. Win32 Processes18.2.3. The Environment (UNIX and Windows)18.2.4. Processes and FilehandlesLogin Information—The getlogin FunctionSpecial Process Variables (pid, uid, euid, gid, euid)The Parent Process ID—The getppid Function and the $$ VariableThe Process Group ID—The pgrp Function18.2.5. Process Priorities and NicenessThe getpriority FunctionThe setpriority Function (nice)18.2.6. Password InformationUNIXWindowsGetting a Password Entry (UNIX)—The getpwent FunctionGetting a Password Entry by Username—The getpwnam FunctionGetting a Password Entry by uid—The getpwuid Function18.2.7. Time and ProcessesThe times functionThe time Function (UNIX and Windows)The gmtime FunctionThe localtime Function18.2.8. Process Creation UNIXThe fork FunctionThe exec FunctionThe wait and waitpid FunctionsThe exit Function18.2.9. Process Creation Win32The start CommandThe Win32::Spawn ModuleThe Win32::Process Module18.3. Other Ways to Interface with the Operating System18.3.1. The syscall Function and the h2ph Script18.3.2. Command Substitution—The Backquotes18.3.3. The Shell.pm Module18.3.4. The system Function18.3.5. here documents18.3.6. Globbing (Filename Expansion and Wildcards)The glob Function18.4. Error HandlingThe Carp.pm Module18.4.1. The die Function18.4.2. The warn Function18.4.3. The eval FunctionEvaluating Perl Expressions with evalUsing eval to Catch Errors in a ProgramThe eval Function and the here document18.5. SignalsCatching SignalsSending Signals to Processes—The kill FunctionThe alarm FunctionThe sleep FunctionAttention, Windows Users!18.6. What You Should Know18.7. What’s Next?
19. Report Writing with Pictures
19.1. The Template19.1.1. Steps in Defining the Template19.1.2. Changing the Filehandle19.1.3. Top-of-the-Page Formatting19.1.4. The select Function19.1.5. Multiline Fields19.1.6. Filling Fields19.1.7. Dynamic Report Writing19.2. What You Should Know19.3. What’s Next?
20. Send It Over the Net and Sock It to ’Em!
20.1. Networking and Perl20.2. Client/Server Model20.3. Network Protocols (TCP/IP)20.3.1. Ethernet Protocol (Hardware)20.3.2. Internet Protocol (IP)20.3.3. Transmission Control Protocol (TCP)20.3.4. User Datagram Protocol (UDP)20.4. Network Addressing20.4.1. Ethernet Addresses20.4.2. IP Addresses20.4.3. Port Numbers20.4.4. Perl Protocol FunctionsThe getprotoent FunctionThe getprotobyname FunctionThe getprotobynumber Function20.4.5. Perl’s Server FunctionsThe getservent FunctionThe getservbyname FunctionThe getservbyport Function20.4.6. Perl’s Host Information FunctionsThe gethostent FunctionThe gethostbyaddr FunctionThe gethostbyname Function20.5. Sockets20.5.1. Types of SocketsStream SocketsDatagram Sockets20.5.2. Socket DomainsThe UNIX Domain and the AF_UNIX FamilyThe Internet Domain and the AF_INET FamilySocket Addresses20.5.3. Creating a Socket20.5.4. Binding an Address to a Socket NameThe bind Function20.5.5. Creating a Socket QueueThe listen Function20.5.6. Waiting for a Client RequestThe accept Function20.5.7. Establishing a Socket ConnectionThe connect Function20.5.8. Socket ShutdownThe shutdown Function20.6. Client/Server Programs20.6.1. Connection-Oriented Sockets on the Same MachineThe Server ProgramThe Client Program20.6.2. Connection-Oriented Sockets on Remote Machines (Internet Clients and Servers)20.7. The Socket.pm ModuleThe ServerThe Client20.8. What You Should Know
A. Perl Built-ins, Pragmas, Modules, and the Debugger
A.1. Perl FunctionsA.2. Special VariablesA.3. Perl PragmasA.4. Perl ModulesA.5. Command-Line SwitchesA.6. DebuggerA.6.1. Getting Information about the DebuggerA.6.2. The Perl DebuggerA.6.3. Entering and Exiting the DebuggerA.6.4. Debugger Commands
B. SQL Language Tutorial
B.1. What Is SQL?B.1.1. Standarizing SQLB.1.2. Executing SQL StatementsThe MySQL Query BrowserB.1.3. About SQL Commands/QueriesEnglish-like GrammarSemicolons Terminate SQL StatementsNaming ConventionsReserved WordsCase SenstivityThe Result SetB.1.4. SQL and the DatabaseThe show databases CommandThe USE CommandB.1.5. SQL Database TablesThe SHOW and DESCRIBE CommandsB.2. SQL Data Manipulation Language (DML)B.2.1. The SELECT CommandSelect Specified ColumnsSelect All ColumnsThe SELECT DISTINCT StatementLimiting the Number of Lines in the Result Set with LIMITThe WHERE ClauseUsing QuotesUsing the = and <> OperatorsWhat Is NULL?The > and < OperatorsThe AND and OR OperatorsThe LIKE and NOT LIKE ConditionPattern Matching and the % WildcardThe _ WildcardThe BETWEEN StatementSorting Results with ORDER BYB.2.2. The INSERT CommandB.2.3. The UPDATE CommandB.2.4. The DELETE StatementB.3. SQL Data Definition LanguageB.3.1. Creating the DatabaseB.3.2. SQL Data TypesB.3.3. Creating a TableB.3.4. Creating a KeyPrimary KeysForeign KeysB.3.5. RelationsTwo Tables with a Common KeyUsing a Fully Qualified Name and a Dot to Join the TablesAliasesB.3.6. Altering a TableB.3.7. Dropping a TableB.3.8. Dropping a DatabaseB.4. SQL FunctionsB.4.1. Numeric FunctionsUsing GROUP BYB.4.2. String FunctionsB.4.3. Date and Time FunctionsFormatting the Date and TimeThe MySQL EXTRACT CommandB.5. Appendix SummaryB.6. What You Should Know
C. Perl and Biology
C.1. What Is Bioinformatics?C.2. A Little Background on DNAC.3. Some Perl ExamplesC.4. What Is BioPerl?C.5. Resources
D. Power and Speed: CGI and mod_perl
D.1. What Is mod_perl?D.2. The mod_perl Web SiteWhat Is mod_perl?Success StoriesDownloadDocumentationReporting BugsGetting HelpMailing ListsProductsContributeGot mod_perl?About mod_perlmod_perl SubprojectsJobsSite MapD.3. Installing mod_perlInstalling mod_perl for ActiveState with PPMApache’s conf Directory (Configuration Files)Editing Apache’s httpd.conf FileCreate the Locations for mod_perl ScriptsWhere Are the Apache Perl Modules Stored?The PerlRequire DirectiveEditing Apache’s httpd.conf FileIs mod_perl Installed?Testing mod_perl with a CGI ScriptUNIX/Linux Installationmod_perl DocumentationConventions Used in the mod_perl Documentationmod_perl 1.0 Documentationmod_perl 2.0 DocumentationGeneral DocumentationOffsite ResourcesD.4. Resources

Content preview from Perl by Example, Fourth Edition

Chapter 11. How Do Subroutines Function?

Subroutines/Functions

In addition to the large number of Perl functions already available, you can create your own functions or subroutines. Some languages distinguish between the terms function and subroutine. Perl doesn’t. If you say “subroutine,” everyone will know you are talking about a “function,” and if you say “function,” everyone will know you are talking about a “subroutine.”^[1] Technically, a function is a block of code that returns a value, whereas a subroutine is a block of code that performs some task, but doesn’t return anything. Perl subroutines and functions can do both, so we’ll use the two ...

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Perl by Example, Fourth Edition

by Ellie Quigley

Chapter 11. How Do Subroutines Function?

Subroutines/Functions

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