perl (manpage)

computing: software: documentation: manpages: perl^m

Manpage

NAME

perl - Practical Extraction and Report Language

SYNOPSIS

perl

1. REDIRECT Template:arg/opt
2. REDIRECT Template:fmt/arg/opt [ <-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> ]...

DESCRIPTION

Perl is a language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information. It's also a good language for many system 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 best features of C, sed, awk, and sh, so people familiar with those languages should have little difficulty with it. (Language historians will also note some vestiges of csh, Pascal, and even BASIC-PLUS.) Expression syntax corresponds closely to C expression syntax. Unlike most Unix utilities, Perl does not arbitrarily 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 of unlimited depth. And the tables used by hashes (sometimes called "associative arrays") grow as necessary to prevent degraded performance. Perl can use sophisticated pattern matching techniques to scan large amounts of data quickly. Although optimized for scanning text, Perl can also deal with binary data, and can make dbm files look like hashes. Setuid Perl scripts are safer than C programs through a dataflow tracing mechanism that prevents many stupid security holes.

If you have a problem that would ordinarily use sed or awk or 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 for you. There are also translators to turn your sed and awk scripts into Perl scripts.

If you're new to Perl, you should start with perlintro, which is a general intro for beginners and provides some background to help you navigate the rest of Perl's extensive documentation.

For ease of access, the Perl manual has been split up into several sections.

Overview

perl	Perl overview (this section)
perlintro	Perl introduction for beginners
perltoc	Perl documentation table of contents

Tutorials

perlreftut	Perl references short introduction [1]
perldsc	Perl data structures intro [2]
perllol	Perl data structures: arrays of arrays [3]
perlrequick	Perl regular expressions quick start
perlretut	Perl regular expressions tutorial
perlboot	Perl OO tutorial for beginners [4]
perltoot	Perl OO tutorial, part 1
perltooc	Perl OO tutorial, part 2
perlbot	Perl OO tricks and examples
perlstyle	Perl style guide
perlcheat	Perl cheat sheet
perltrap	Perl traps for the unwary
perldebtut	Perl debugging tutorial
perlfaq	Perl frequently asked questions
	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

Reference Manual

perlsyn	Perl syntax
perldata	Perl data structures
perlop	Perl operators and precedence
perlsub	Perl subroutines
perlfunc	Perl built-in functions
	perlopentut Perl open() tutorial perlpacktut Perl pack() and unpack() tutorial
perlpod	Perl plain old documentation
perlpodspec	Perl plain old documentation format specification
perlrun	Perl execution and options
perldiag	Perl diagnostic messages
perllexwarn	Perl warnings and their control
perldebug	Perl debugging
perlvar	Perl predefined variables
perlre	Perl regular expressions, the rest of the story
perlreref	Perl regular expressions quick reference
perlref	Perl references, the rest of the story
perlform	Perl formats
perlobj	Perl objects
perltie	Perl objects hidden behind simple variables perldbmfilter Perl DBM filters
perlipc	Perl interprocess communication
perlfork	Perl fork() information
perlnumber	Perl number semantics
perlthrtut	Perl threads tutorial perlothrtut Old Perl threads tutorial
perlport	Perl portability guide
perllocale	Perl locale support
perluniintro	Perl Unicode introduction
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
perlmodstyle	Perl modules: how to write modules with style
perlmodinstall	Perl modules: how to install from CPAN
perlnewmod	Perl modules: preparing a new module for distribution
perlutil	utilities packaged with the Perl distribution
perlcompile	Perl compiler suite intro
perlfilter	Perl source filters

Internals and C Language Interface

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
perlapi	Perl API listing (autogenerated)
perlintern	Perl internal functions (autogenerated)
perliol	C API for Perl's implementation of IO in Layers
perlapio	Perl internal IO abstraction interface
perlhack	Perl hackers guide

Miscellaneous

perlbook	Perl book information
perltodo	Perl things to do
perldoc	Look up Perl documentation in Pod format
perlhist	Perl history records
perldelta	Perl changes since previous version
perl583delta	Perl changes in version 5.8.3
perl582delta	Perl changes in version 5.8.2
perl581delta	Perl changes in version 5.8.1
perl58delta	Perl changes in version 5.8.0
perl573delta	Perl changes in version 5.7.3
perl572delta	Perl changes in version 5.7.2
perl571delta	Perl changes in version 5.7.1
perl570delta	Perl changes in version 5.7.0
perl561delta	Perl changes in version 5.6.1
perl56delta	Perl changes in version 5.6
perl5005delta	Perl changes in version 5.005
perl5004delta	Perl changes in version 5.004
perlartistic	Perl Artistic License
perlgpl	GNU General Public License

Language-Specific

perlcn	Perl for Simplified Chinese (in EUC-CN)
perljp	Perl for Japanese (in EUC-JP)
perlko	Perl for Korean (in EUC-KR)
perltw	Perl for Traditional Chinese (in Big5)

Platform-Specific

perlaix	Perl notes for AIX
perlamiga	Perl notes for AmigaOS
perlapollo	Perl notes for Apollo DomainOS
perlbeos	Perl notes for BeOS
perlbs2000	Perl notes for POSIX-BC BS2000
perlce	Perl notes for WinCE
perlcygwin	Perl notes for Cygwin
perldgux	Perl notes for DG/UX
perldos	Perl notes for DOS
perlepoc	Perl notes for EPOC
perlfreebsd	Perl notes for FreeBSD
perlhpux	Perl notes for HP-UX
perlhurd	Perl notes for Hurd
perlirix	Perl notes for Irix
perlmachten	Perl notes for Power MachTen
perlmacos	Perl notes for Mac OS (Classic)
perlmacosx	Perl notes for Mac OS X
perlmint	Perl notes for MiNT
perlmpeix	Perl notes for MPE/iX
perlnetware	Perl notes for NetWare
perlos2	Perl notes for OS/2
perlos390	Perl notes for OS/390
perlos400	Perl notes for OS/400
perlplan9	Perl notes for Plan 9
perlqnx	Perl notes for QNX
perlsolaris	Perl notes for Solaris
perltru64	Perl notes for Tru64
perluts	Perl notes for UTS
perlvmesa	Perl notes for VM/ESA
perlvms	Perl notes for VMS
perlvos	Perl notes for Stratus VOS
perlwin32	Perl notes for Windows

On Debian systems, you need to install the perl-doc package which contains the majority of the standard Perl documentation and the perldoc program.

Extensive additional documentation for Perl modules is available, both those distributed with Perl and third-party modules which are packaged or locally installed.

You should be able to view Perl's documentation with your man(1) program or perldoc(1).

If something strange has gone wrong with your program and you're not sure where you should look for help, try the -w switch first. It will often point out exactly where the trouble is.

But wait, there's more...

Begun in 1993 (see perlhist), Perl version 5 is nearly a complete rewrite that provides the following additional benefits:

• modularity and reusability using innumerable modules

  Described in perlmod, perlmodlib, and perlmodinstall.

• embeddable and extensible

  Described in perlembed, perlxstut, perlxs, perlcall, perlguts, and xsubpp.

• roll-your-own magic variables (including multiple simultaneous DBM implementations)

  Described in Template:manppagelink and AnyDBM_File.

• subroutines can now be overridden, autoloaded, and prototyped

  Described in perlsub.

• arbitrarily nested data structures and anonymous functions

  Described in perlreftut, perlref, perldsc, and perllol.

• object-oriented programming

  Described in perlobj, perlboot, perltoot, perltooc, and perlbot.

• support for light-weight processes (threads)

  Described in perlthrtut and threads.

• support for Unicode, internationalization, and localization

  Described in perluniintro, perllocale and Locale::Maketext.

• lexical scoping

  Described in perlsub.

• regular expression enhancements

  Described in perlre, with additional examples in perlop.

• enhanced debugger and interactive Perl environment, with integrated editor support

  Described in perldebtut, perldebug and perldebguts.

• POSIX 1003.1 compliant library

  Described in POSIX.

Okay, that's definitely enough hype.

AVAILABILITY

Perl is available for most operating systems, including virtually all Unix-like platforms. See "Supported Platforms" in perlport for a listing.

ENVIRONMENT

See perlrun.

AUTHOR

Larry Wall larryspam@spamwallspam.spamorg, 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-thanksspam@spamperlspam.spamorg.

FILES

"@INC"

locations of perl libraries

SEE ALSO

• a2p: awk to perl translator
• s2p: sed to perl translator

• http://www.perl.com/ the Perl Home Page
• http://www.cpan.org/ the Comprehensive Perl Archive
• http://www.perl.org/ Perl Mongers (Perl user groups)

DIAGNOSTICS

The "use warnings" pragma (and the -w switch) produces some lovely diagnostics.

See perldiag for explanations of all Perl's diagnostics. The "use diagnostics" pragma automatically turns Perl's normally terse warnings and errors into these longer forms.

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

Setuid scripts have additional constraints that can produce error messages such as "Insecure dependency". See perlsec.

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

BUGS

The -w switch is not mandatory.

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

If your stdio requires a seek or eof between reads and writes on a particular 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: a given variable name may not be longer than 251 characters. Line numbers displayed by diagnostics are internally stored as short integers, so they are limited to a maximum of 65535 (higher numbers usually being affected by wraparound).

You may mail your bug reports (be sure to include full configuration information as output by the myconfig program in the perl source tree, or by "perl -V") to perlbugspam@spamperlspam.spamorg. 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, but don't tell anyone I said that.

NOTES

The Perl motto is "There's more than one way to do it." Divining how 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.