Virtual Solutions : Resources : Documentation : Perl POD : perl - Practical Extraction and Report Language


NAME

perl - Practical Extraction and Report Language

SYNOPSIS

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

If you're new to Perl, you should start with the perlintro manpage , 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
  • perldsc Perl data structures intro
  • perllol Perl data structures: arrays of arrays

Reference Manual

  • perlutil utilities packaged with the Perl distribution

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

Miscellaneous

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

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

Extensive additional documentation for Perl modules is available. The default configuration for perl will place this additional documentation in the /usr/local/lib/perl5/man directory (or else in the man subdirectory of the Perl library directory). Some of this additional documentation is distributed standard with Perl, but you'll also find documentation 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-up files, or in the MANPATH environment variable. To find out where the configuration has installed the manpages, type:

perl -V:man.dir

If the directories have a common stem, such as /usr/local/man/man1 and /usr/local/man/man3, you need only to add that stem (/usr/local/man) to your man(1) configuration files or your MANPATH environment variable. If they do not share a stem, you'll have to add both stems.

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

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.

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.

But wait, there's more...

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

Okay, that's definitely enough hype..

AVAILABILITY

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

ENVIRONMENT

See the perlrun manpage .

AUTHOR

Larry Wall <larry@wall.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-thanks@perl.org .

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 the perldiag manpage for explanations of all Perl's diagnostics. The CCompilation 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 the perlsec manpage .

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 perlbug@perl.org . 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.




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