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=head1 NAME
perl - Practical Extraction and Report Language
=head1 SYNOPSIS
B<perl> S<[ B<-sTuU> ]> S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]> S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]> S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]> S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]> S<[ B<-P> ]> S<[ B<-S> ]> S<[ B<-x>[I<dir>] ]> S<[ B<-i>[I<extension>] ]> S<[ B<-e> I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
For ease of access, the Perl manual has been split up into several sections:
perl Perl overview (this section) perlfaq Perl frequently asked questions perltoc Perl documentation table of contents perlbook Perl book information
perlsyn Perl syntax perldata Perl data structures perlop Perl operators and precedence perlsub Perl subroutines perlfunc Perl builtin functions perlreftut Perl references short introduction perldsc Perl data structures intro perlrequick Perl regular expressions quick start perlpod Perl plain old documentation perlstyle Perl style guide perltrap Perl traps for the unwary
perlrun Perl execution and options perldiag Perl diagnostic messages perllexwarn Perl warnings and their control perldebtut Perl debugging tutorial perldebug Perl debugging
perlvar Perl predefined variables perllol Perl data structures: arrays of arrays perlopentut Perl open() tutorial perlretut Perl regular expressions tutorial
perlre Perl regular expressions, the rest of the story perlref Perl references, the rest of the story
perlform Perl formats
perlboot Perl OO tutorial for beginners perltoot Perl OO tutorial, part 1 perltootc Perl OO tutorial, part 2 perlobj Perl objects perlbot Perl OO tricks and examples perltie Perl objects hidden behind simple variables
perlipc Perl interprocess communication perlfork Perl fork() information perlnumber Perl number semantics perlthrtut Perl threads tutorial
perlport Perl portability guide perllocale Perl locale support perlunicode Perl unicode support perlebcdic Considerations for running Perl on EBCDIC platforms
perlsec Perl security
perlmod Perl modules: how they work perlmodlib Perl modules: how to write and use perlmodinstall Perl modules: how to install from CPAN perlnewmod Perl modules: preparing a new module for distribution
perlfaq1 General Questions About Perl perlfaq2 Obtaining and Learning about Perl perlfaq3 Programming Tools perlfaq4 Data Manipulation perlfaq5 Files and Formats perlfaq6 Regexes perlfaq7 Perl Language Issues perlfaq8 System Interaction perlfaq9 Networking
perlcompile Perl compiler suite intro
perlembed Perl ways to embed perl in your C or C++ application perldebguts Perl debugging guts and tips perlxstut Perl XS tutorial perlxs Perl XS application programming interface perlclib Internal replacements for standard C library functions perlguts Perl internal functions for those doing extensions perlcall Perl calling conventions from C perlutil utilities packaged with the Perl distribution perlfilter Perl source filters perldbmfilter Perl DBM filters perlapi Perl API listing (autogenerated) perlintern Perl internal functions (autogenerated) perlapio Perl internal IO abstraction interface perltodo Perl things to do perlhack Perl hackers guide
perlhist Perl history records perldelta Perl changes since previous version perl5005delta Perl changes in version 5.005 perl5004delta Perl changes in version 5.004
perlaix Perl notes for AIX perlamiga Perl notes for Amiga perlbs2000 Perl notes for POSIX-BC BS2000 perlcygwin Perl notes for Cygwin perldos Perl notes for DOS perlepoc Perl notes for EPOC perlhpux Perl notes for HP-UX perlmachten Perl notes for Power MachTen perlmacos Perl notes for Mac OS (Classic) perlmpeix Perl notes for MPE/iX perlos2 Perl notes for OS/2 perlos390 Perl notes for OS/390 perlsolaris Perl notes for Solaris perlvmesa Perl notes for VM/ESA perlvms Perl notes for VMS perlvos Perl notes for Stratus VOS perlwin32 Perl notes for Windows
(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, the manpages listed above are installed in the F</usr/local/man/> directory.
Extensive additional documentation for Perl modules is available. Thedefault configuration for perl will place this additional documentationin the F</usr/local/lib/perl5/man> directory (or else in the F<man>subdirectory 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 F</usr/local/man/man1>and F</usr/local/man/man3>, you need only to add that stem(F</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 F<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 B<-w> switch first. Itwill often point out exactly where the trouble is.
=head1 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, B<sed>, B<awk>, and B<sh>, so people familiar withthose languages should have little difficulty with it. (Languagehistorians will also note some vestiges of B<csh>, Pascal, and evenBASIC-PLUS.) Expression syntax corresponds 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 (sometimes called"associative arrays") grow as necessary to prevent degradedperformance. Perl can use sophisticated pattern matching techniques toscan large amounts of data 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 that prevents many stupidsecurity holes.
If you have a problem that would ordinarily use B<sed> or B<awk> orB<sh>, 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 B<sed> and B<awk>scripts into Perl scripts.
But wait, there's more...
Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a completerewrite that provides the following additional benefits:
=over 4
=item *
modularity and reusability using innumerable modules
Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
=item *
embeddable and extensible
Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,L<perlguts>, and L<xsubpp>.
=item *
roll-your-own magic variables (including multiple simultaneous DBM implementations)
Described in L<perltie> and L<AnyDBM_File>.
=item *
subroutines can now be overridden, autoloaded, and prototyped
Described in L<perlsub>.
=item *
arbitrarily nested data structures and anonymous functions
Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
=item *
object-oriented programming
Described in L<perlobj>, L<perltoot>, and L<perlbot>.
=item *
compilability into C code or Perl bytecode
Described in L<B> and L<B::Bytecode>.
=item *
support for light-weight processes (threads)
Described in L<perlthrtut> and L<Thread>.
=item *
support for internationalization, localization, and Unicode
Described in L<perllocale> and L<utf8>.
=item *
lexical scoping
Described in L<perlsub>.
=item *
regular expression enhancements
Described in L<perlre>, with additional examples in L<perlop>.
=item *
enhanced debugger and interactive Perl environment,with integrated editor support
Described in L<perldebug>.
=item *
POSIX 1003.1 compliant library
Described in L<POSIX>.
=back
Okay, that's I<definitely> enough hype.
=head1 AVAILABILITY
Perl is available for most operating systems, including virtuallyall Unix-like platforms. See L<perlport/"Supported Platforms">for a listing.
=head1 ENVIRONMENT
See L<perlrun>.
=head1 AUTHOR
Larry Wall <[email protected]>, 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 [email protected] .
=head1 FILES
"@INC" locations of perl libraries
=head1 SEE ALSO
a2p awk to perl translator s2p sed to perl translator
http://www.perl.com/ the Perl Home Page http://www.perl.com/CPAN the Comprehensive Perl Archive
=head1 DIAGNOSTICS
The C<use warnings> pragma (and the B<-w> switch) produces some lovely diagnostics.
See L<perldiag> for explanations of all Perl's diagnostics. The C<usediagnostics> pragma automatically turns Perl's normally terse warningsand errors into these longer forms.
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 a script passed to Perl via B<-e> switches, eachB<-e> is counted as one line.)
Setuid scripts have additional constraints that can produce errormessages such as "Insecure dependency". See L<perlsec>.
Did we mention that you should definitely consider using the B<-w>switch?
=head1 BUGS
The B<-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 251 characters. Line numbersdisplayed by diagnostics are internally stored as short integers,so they are limited to a maximum of 65535 (higher numbers usually beingaffected by wraparound).
You may mail your bug reports (be sure to include full configurationinformation as output by the myconfig program in the perl sourcetree, or by C<perl -V>) to [email protected] . If you've succeededin compiling perl, the B<perlbug> script in the F<utils/> subdirectorycan be used to help mail in a bug report.
Perl actually stands for Pathologically Eclectic Rubbish Lister, butdon't tell anyone I said that.
=head1 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.
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