MAN page from Old RedHat 5.X perl-5.004-4.i386.rpm

PERL

Section: Perl Programmers Reference Guide (1)
Updated: perl 5.004, patch 04
Index

NAME

perl - Practical Extraction and Report Language

SYNOPSIS

perl   [ -sTuU ]
        [ -hv ] [ -V[:configvar] ]
        [ -cw ] [ -d[:debugger] ] [ -D[number/list] ]
        [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal] ]
        [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ]
        [ -P ]
        [ -S ]
        [ -x[dir] ]
        [ -i[extension] ]
        [ -e 'command' ] [ -- ] [ programfile ] [ argument ]...

For ease of access, the Perl manual has been split up into a numberof sections:

    perl        Perl overview (this section)    perldelta   Perl changes since previous version    perlfaq     Perl frequently asked questions

    perldata    Perl data structures    perlsyn     Perl syntax    perlop      Perl operators and precedence    perlre      Perl regular expressions    perlrun     Perl execution and options    perlfunc    Perl builtin functions    perlvar     Perl predefined variables    perlsub     Perl subroutines    perlmod     Perl modules: how they work    perlmodlib  Perl modules: how to write and use    perlform    Perl formats    perllocale  Perl locale support

    perlref     Perl references    perldsc     Perl data structures intro    perllol     Perl data structures: lists of lists    perltoot    Perl OO tutorial    perlobj     Perl objects    perltie     Perl objects hidden behind simple variables    perlbot     Perl OO tricks and examples    perlipc     Perl interprocess communication

    perldebug   Perl debugging    perldiag    Perl diagnostic messages    perlsec     Perl security    perltrap    Perl traps for the unwary    perlstyle   Perl style guide

    perlpod     Perl plain old documentation    perlbook    Perl book information

    perlembed   Perl ways to embed perl in your C or C++ application    perlapio    Perl internal IO abstraction interface    perlxs      Perl XS application programming interface    perlxstut   Perl XS tutorial    perlguts    Perl internal functions for those doing extensions    perlcall    Perl calling conventions from C

(If you're intending to read these straight through for the first time,the suggested order will tend to reduce the number of forward references.)

By default, all of the above manpages are installed in the /usr/local/man/ directory.

Extensive additional documentation for Perl modules is available. Thedefault configuration for perl will place this additional documentationin the /usr/local/lib/perl5/man directory (or else in the mansubdirectory of the Perl library directory). Some of this additionaldocumentation is distributed standard with Perl, but you'll also finddocumentation for third-party modules there.

You should be able to view Perl's documentation with your man(1)program by including the proper directories in the appropriate start-upfiles, or in the MANPATH environment variable. To find out where theconfiguration has installed the manpages, type:

    perl -V:man.dir

If the directories have a common stem, such as /usr/local/man/man1and /usr/local/man/man3, you need only to add that stem(/usr/local/man) to your man(1) configuration files or your MANPATHenvironment variable. If they do not share a stem, you'll have to addboth stems.

If that doesn't work for some reason, you can still use thesupplied perldoc script to view module information. You mightalso look into getting a replacement man program.

If something strange has gone wrong with your program and you're notsure where you should look for help, try the -w switch first. Itwill often point out exactly where the trouble is.

DESCRIPTION

Perl is a language optimized for scanning arbitrarytext files, extracting information from those text files, and printingreports based on that information. It's also a good language for manysystem management tasks. The language is intended to be practical(easy to use, efficient, complete) rather than beautiful (tiny,elegant, minimal).

Perl combines (in the author's opinion, anyway) some of the bestfeatures of C, sed, awk, and sh, so people familiar withthose languages should have little difficulty with it. (Languagehistorians will also note some vestiges of csh, Pascal, and evenBASIC-PLUS.) Expression syntax corresponds quite closely to Cexpression syntax. Unlike most Unix utilities, Perl does notarbitrarily limit the size of your data---if you've got the memory,Perl can slurp in your whole file as a single string. Recursion is ofunlimited depth. And the tables used by hashes (previously called``associative arrays") grow as necessary to prevent degradedperformance. Perl uses sophisticated pattern matching techniques toscan large amounts of data very quickly. Although optimized forscanning text, Perl can also deal with binary data, and can make dbmfiles look like hashes. Setuid Perl scripts are safer than C programsthrough a dataflow tracing mechanism which prevents many stupidsecurity holes.

If you have a problem that would ordinarily use sed or awk orsh, but it exceeds their capabilities or must run a little faster,and you don't want to write the silly thing in C, then Perl may be foryou. There are also translators to turn your sed and awkscripts into Perl scripts.

But wait, there's more...

Perl version 5 is nearly a complete rewrite, and providesthe following additional benefits:

* Many usability enhancements: It is now possible to write much more readable Perl code (even withinregular expressions). Formerly cryptic variable names can be replacedby mnemonic identifiers. Error messages are more informative, and theoptional warnings will catch many of the mistakes a novice might make.This cannot be stressed enough. Whenever you get mysterious behavior,try the -w switch!!! Whenever you don't get mysterious behavior,try using -w anyway.
* Simplified grammar: The new yacc grammar is one half the size of the old one. Many of thearbitrary grammar rules have been regularized. The number of reservedwords has been cut by 2/3. Despite this, nearly all old Perl scriptswill continue to work unchanged.
* Lexical scoping: Perl variables may now be declared within a lexical scope, like ``auto''variables in C. Not only is this more efficient, but it contributesto better privacy for ``programming in the large''. Anonymoussubroutines exhibit deep binding of lexical variables (closures).
* Arbitrarily nested data structures: Any scalar value, including any array element, may now contain areference to any other variable or subroutine. You can easily createanonymous variables and subroutines. Perl manages your referencecounts for you.
* Modularity and reusability: The Perl library is now defined in terms of modules which can be easilyshared among various packages. A package may choose to import all or aportion of a module's published interface. Pragmas (that is, compilerdirectives) are defined and used by the same mechanism.
* Object-oriented programming: A package can function as a class. Dynamic multiple inheritance andvirtual methods are supported in a straightforward manner and with verylittle new syntax. Filehandles may now be treated as objects.
* Embeddable and Extensible: Perl may now be embedded easily in your C or C++ application, and caneither call or be called by your routines through a documentedinterface. The XS preprocessor is provided to make it easy to glueyour C or C++ routines into Perl. Dynamic loading of modules issupported, and Perl itself can be made into a dynamic library.
* POSIX compliant: A major new module is the POSIX module, which provides access to allavailable POSIX routines and definitions, via object classes whereappropriate.
* Package constructors and destructors: The new BEGIN and END blocks provide means to capture control asa package is being compiled, and after the program exits. As adegenerate case they work just like awk's BEGIN and END when youuse the -p or -n switches.
* Multiple simultaneous DBM implementations: A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DBfiles from the same script simultaneously. In fact, the old dbmopeninterface has been generalized to allow any variable to be tiedto an object class which defines its access methods.
* Subroutine definitions may now be autoloaded: In fact, the AUTOLOAD mechanism also allows you to define any arbitrarysemantics for undefined subroutine calls. It's not for just autoloading.
* Regular expression enhancements: You can now specify nongreedy quantifiers. You can now do groupingwithout creating a backreference. You can now write regular expressionswith embedded whitespace and comments for readability. A consistentextensibility mechanism has been added that is upwardly compatible withall old regular expressions.
* Innumerable Unbundled Modules: The Comprehensive Perl Archive Network described in the perlmodlib manpagecontains hundreds of plug-and-play modules full of reusable code.See http://www.perl.com/CPAN for a site near you.
* Compilability: While not yet in full production mode, a working perl-to-C compilerdoes exist. It can generate portable byte code, simple C, oroptimized C code.

Okay, that's definitely enough hype.

ENVIRONMENT

See the perlrun manpage.

AUTHOR

Larry Wall <larryAATTwall.org>, with the help of oodles of other folks.

If your Perl success stories and testimonials may be of help to others who wish to advocate the use of Perl in their applications, or if you wish to simply express your gratitude to Larry and the Perl developers, please write to <perl-thanksAATTperl.org>.

FILES

 "/tmp/perl-e$$"        temporary file for -e commands "@INC"                 locations of perl libraries

DIAGNOSTICS

The -w switch produces some lovely diagnostics.

See the perldiag manpage for explanations of all Perl's diagnostics.

Compilation errors will tell you the line number of the error, with anindication of the next token or token type that was to be examined.(In the case of a script passed to Perl via -e switches, each-e is counted as one line.)

Setuid scripts have additional constraints that can produce errormessages such as ``Insecure dependency''. See the perlsec manpage.

Did we mention that you should definitely consider using the -wswitch?

BUGS

The -w switch is not mandatory.

Perl is at the mercy of your machine's definitions of variousoperations such as type casting, atof(), and floating-pointoutput with sprintf().

If your stdio requires a seek or eof between reads and writes on aparticular stream, so does Perl. (This doesn't apply to sysread()and syswrite().)

While none of the built-in data types have any arbitrary size limits(apart from memory size), there are still a few arbitrary limits: agiven variable name may not be longer than 255 characters, and nocomponent of your PATH may be longer than 255 if you use -S. A regularexpression may not compile to more than 32767 bytes internally.

You may mail your bug reports (be sure to include full configurationinformation as output by the myconfig program in the perl source tree,or by perl -V) to <perlbugAATTperl.com>.If you've succeeded in compiling perl, the perlbug script in the utils/subdirectory can be used to help mail in a bug report.

Perl actually stands for Pathologically Eclectic Rubbish Lister, butdon't tell anyone I said that.

NOTES

The Perl motto is ``There's more than one way to do it.'' Divininghow many more is left as an exercise to the reader.

The three principal virtues of a programmer are Laziness,Impatience, and Hubris. See the Camel Book for why.

This document was created byman2html,using the manual pages.