NAME


perl - Practical Extraction and Report Language

SYNOPSIS


perl    [ -sTtuUWX ]         [ -hv ] [ -V[:configvar] ]         [ -cw ] [ -d[t][:debugger] ] [ -D[number/list] ]         [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadecimal] ]         [ -Idir ] [ -m[-]module ] [ -M[-]’module...’ ] [ -f ]         [ -C [number/list] ]         [ -P ]         [ -S ]         [ -x[dir] ]         [ -i[extension] ]         [ -e ’command’ ] [ -- ] [ programfile ] [ argument ]...

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


Tutorials


Reference Manual


Internals and C Language Interface


Miscellaneous


Language-Specific


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 perlhist), Perl version 5 is nearly a complete rewrite that provides the following additional benefits:
o modularity and reusability using innumerable modules

Described in perlmod, perlmodlib, and perlmodinstall.

o embeddable and extensible

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

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

Described in perltie and AnyDBM_File.

o subroutines can now be overridden, autoloaded, and prototyped

Described in perlsub.

o arbitrarily nested data structures and anonymous functions

Described in perlreftut, perlref, perldsc, and perllol.

o object-oriented programming

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

o support for light-weight processes (threads)

Described in perlthrtut and threads.

o support for Unicode, internationalization, and localization

Described in perluniintro, perllocale and Locale::Maketext.

o lexical scoping

Described in perlsub.

o regular expression enhancements

Described in perlre, with additional examples in perlop.

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

Described in perldebtut, perldebug and perldebguts.

o 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 <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


SEE ALSO


http://www.perl.org/ the Perl homepage http://www.perl.com/ Perl articles (OReilly) http://www.cpan.org/ the Comprehensive Perl Archive http://www.pm.org/ the Perl Mongers

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 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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