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Chapter 7 |  |
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Chapter 7 | |
Contents:
Beyond the Standard Library
Library Modules
This chapter describes the collection of Perl code that comes along with the Perl distribution. If you use this library and then share your program with others, they will not have to take special steps to execute the program, because the same library is available to Perl programs everywhere.
You'll save some time if you make the effort to get familiar with the standard library. There's no point in reinventing the wheel. You should be aware, however, that the library contains a wide range of material. While some modules may be extremely helpful, others may be completely irrelevant to your needs. For example, some are useful only if you are creating extensions to Perl. We offer below a rough classification of the library modules to aid you in browsing.
First, however, let's untangle some terminology:
A package is a simple namespace management device, allowing two different parts of a Perl program to have a (different) variable named $fred. These namespaces are managed with the package declaration, described in Chapter 5, Packages, Modules, and Object Classes.
A library is a set of subroutines for a particular purpose. Often the library declares itself a separate package so that related variables and subroutines can be kept together, and so that they won't interfere with other variables in your program. Generally, a library is placed in a separate file, often ending in ".pl ", and then pulled into the main program via require. (This mechanism has largely been superseded by the module mechanism, so nowadays we often use the term "library" to talk about the whole system of modules that come with Perl. See the title of this chapter, for instance.)
A module is a library that conforms to specific conventions, allowing the file to be brought in with a use directive at compile time. Module filenames end in ".pm", because the use directive insists on that. (It also translates the subpackage delimiter :: to whatever your subdirectory delimiter is; it is / on UNIX.) Chapter 5, Packages, Modules, and Object Classes describes Perl modules in greater detail.
A pragma is a module that affects the compilation phase of your program as well as the execution phase. Think of them as hints to the compiler. Unlike modules, pragmas often (but not always) limit the scope of their effects to the innermost enclosing block of your program. The names of pragmas are by convention all lowercase.
For easy reference, this chapter is arranged alphabetically. If you wish to look something up by functional grouping, Tables 7-1 through 7-11 display an (admittedly arbitrary) listing of the modules and pragmas described in this chapter.
| Module | Function |
|---|---|
| Benchmark | Check and compare running times of code |
| Config | Access Perl configuration information |
| Env | Import environment variables |
| English | Use English or awk names for punctuation variables |
| Getopt::Long | Extended processing of command-line options |
| Getopt::Std | Process single-character switches with switch clustering |
| lib | Manipulate @INC at compile time |
| Shell | Run shell commands transparently within Perl |
| strict | Restrict unsafe constructs |
| Symbol | Generate anonymous globs; qualify variable names |
| subs | Predeclare subroutine names |
| vars | Predeclare global variable names |
| Module | Function |
|---|---|
| Carp | Generate error messages |
| diagnostics | Force verbose warning diagnostics |
| sigtrap | Enable stack backtrace on unexpected signals |
| Sys::Syslog | Perl interface to UNIX syslog (3) calls |
| Module | Function |
|---|---|
| Cwd | Get pathname of current working directory |
| DirHandle | Supply object methods for directory handles |
| File::Basename | Parse file specifications |
| File::CheckTree | Run many tests on a collection of files |
| File::Copy | Copy files or filehandles |
| File::Find | Traverse a file tree |
| File::Path | Create or remove a series of directories |
| FileCache | Keep more files open than the system permits |
| FileHandle | Supply object methods for filehandles |
| SelectSaver | Save and restore selected filehandle |
| Module | Function |
|---|---|
| Pod::Text | Convert POD data to formatted ASCII text |
| Search::Dict | Search for key in dictionary file |
| Term::Cap | Terminal capabilities interface |
| Term::Complete | Word completion module |
| Text::Abbrev | Create an abbreviation table from a list |
| Text::ParseWords | Parse text into a list of tokens |
| Text::Soundex | The Soundex Algorithm described by Knuth |
| Text::Tabs | Expand and unexpand tabs |
| Text::Wrap | Wrap text into a paragraph |
| Module | Function |
|---|---|
| AnyDBM_File | Provide framework for multiple DBMs |
| DB_File | Tied access to Berkeley DB |
| GDBM_File | Tied access to GDBM library |
| NDBM_File | Tied access to NDBM files |
| ODBM_File | Tied access to ODBM files |
| SDBM_File | Tied access to SDBM files |
| Module | Function |
|---|---|
| integer | Do arithmetic in integer instead of double |
| Math::BigFloat | Arbitrary-length floating-point math package |
| Math::BigInt | Arbitrary-length integer math package |
| Math::Complex | Complex numbers package |
| Module | Function |
|---|---|
| IPC::Open2 | Open a process for both reading and writing |
| IPC::Open3 | Open a process for reading, writing, and error handling |
| Net::Ping | Check whether a host is online |
| Socket | Load the C socket.h defines and structure manipulators |
| Sys::Hostname | Try every conceivable way to get hostname |
| Module | Function |
|---|---|
| Time::Local | Efficiently compute time from local and GMT time |
| I18N::Collate | Compare 8-bit scalar data according to the current locale |
| Module | Function |
|---|---|
| AutoLoader | Load functions only on demand |
| AutoSplit | Split a module for autoloading |
| Devel::SelfStubber | Generate stubs for a SelfLoading module |
| DynaLoader | Automatic dynamic loading of Perl modules |
| SelfLoader | Load functions only on demand |
| Module | Function |
|---|---|
| ExtUtils::Install | Install files from here to there |
| ExtUtils::Liblist | Determine libraries to use and how to use them |
| ExtUtils::MakeMaker | Create a Makefile for a Perl extension |
| ExtUtils::Manifest | Utilities to write and check a MANIFEST file |
| ExtUtils::Miniperl | Write the C code for perlmain.c |
| ExtUtils::Mkbootstrap | Make a bootstrap file for use by DynaLoader |
| ExtUtils::Mksymlists | Write linker option files for dynamic extension |
| ExtUtils::MM_OS2 | Methods to override UNIX behavior in ExtUtils::MakeMaker |
| ExtUtils::MM_Unix | Methods used by ExtUtils::MakeMaker |
| ExtUtils::MM_VMS | Methods to override UNIX behavior in ExtUtils::MakeMaker |
| Fcntl | Load the C fcntl.h defines |
| POSIX | Interface to IEEE Std 1003.1 |
| Safe | Create safe namespaces for evaluating Perl code |
| Test::Harness | Run Perl standard test scripts with statistics |
| Module | Function |
|---|---|
| Exporter | Default import method for modules |
| overload | Overload Perl's mathematical operations |
| Tie::Hash | Base class definitions for tied hashes |
| Tie::Scalar | Base class definitions for tied scalars |
| Tie::StdHash | Base class definitions for tied hashes |
| Tie::StdScalar | Base class definitions for tied scalars |
| Tie::SubstrHash | Fixed-table-size, fixed-key-length hashing |
If you don't find an entry in the standard library that fits your needs, it's still quite possible that someone has written code that will be useful to you. There are many superb library modules that are not included in the standard distribution, for various practical, political, and pathetic reasons. To find out what is available, you can look at the Comprehensive Perl Archive Network (CPAN). See the discussion of CPAN in the Preface.
Here are the major categories of modules available from CPAN:
Allow us again to reiterate once more that these things are in a state of flux, and you will certainly find more and better stuff on CPAN than we can possibly describe here. The Perl of Great Price has outgrown its oyster, so to speak, because Perl is truly a community effort these days--see John 14:12.
