perl (manpage)

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Manpage

NAME

perl - Practical Extraction and Report Language

SYNOPSIS

perl

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

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

Tutorials

perlreftut (CPAN) Perl references short introduction
perldsc (CPAN) Perl data structures intro
perllol (CPAN) Perl data structures: arrays of arrays
perlrequick (CPAN) Perl regular expressions quick start
perlretut (CPAN) Perl regular expressions tutorial
perlboot (CPAN) Perl OO tutorial for beginners
perltoot (CPAN) Perl OO tutorial, part 1
perltooc (CPAN) Perl OO tutorial, part 2
perlbot (CPAN) Perl OO tricks and examples
perlstyle (CPAN) Perl style guide
perlcheat (CPAN) Perl cheat sheet
perltrap (CPAN) Perl traps for the unwary
perldebtut (CPAN) Perl debugging tutorial
perlfaq (CPAN) Perl frequently asked questions
perlfaq1 (CPAN) General Questions About Perl
perlfaq2 (CPAN) Obtaining and Learning about Perl
perlfaq3 (CPAN) Programming Tools
perlfaq4 (CPAN) Data Manipulation
perlfaq5 (CPAN) Files and Formats
perlfaq6 (CPAN) Regexes
perlfaq7 (CPAN) Perl Language Issues
perlfaq8 (CPAN) System Interaction
perlfaq9 (CPAN) Networking

Reference Manual

perlsyn (CPAN) Perl syntax
perldata (CPAN) Perl data structures
perlop (CPAN) Perl operators and precedence
perlsub (CPAN) Perl subroutines
perlfunc (CPAN) Perl built-in functions
perlopentut (CPAN) Perl open() tutorial
perlpacktut (CPAN) Perl pack() and unpack() tutorial
perlpod (CPAN) Perl plain old documentation
perlpodspec (CPAN) Perl plain old documentation format specification
perlrun (CPAN) Perl execution and options
perldiag (CPAN) Perl diagnostic messages
perllexwarn (CPAN) Perl warnings and their control
perldebug (CPAN) Perl debugging
perlvar (CPAN) Perl predefined variables
perlre (CPAN) Perl regular expressions, the rest of the story
perlreref (CPAN) Perl regular expressions quick reference
perlref (CPAN) Perl references, the rest of the story
perlform (CPAN) Perl formats
perlobj (CPAN) Perl objects
perltie (CPAN) Perl objects hidden behind simple variables
perldbmfilter Perl DBM filters
perlipc (CPAN) Perl interprocess communication
perlfork (CPAN) Perl fork() information
perlnumber (CPAN) Perl number semantics
perlthrtut (CPAN) Perl threads tutorial
perlothrtut (CPAN) Old Perl threads tutorial
perlport (CPAN) Perl portability guide
perllocale (CPAN) Perl locale support
perluniintro (CPAN) Perl Unicode introduction
perlunicode (CPAN) Perl Unicode support
perlebcdic (CPAN) Considerations for running Perl on EBCDIC platforms

perlsec (CPAN) Perl security

perlmod (CPAN) Perl modules: how they work
perlmodlib (CPAN) Perl modules: how to write and use
perlmodstyle (CPAN) Perl modules: how to write modules with style
perlmodinstall (CPAN) Perl modules: how to install from CPAN
perlnewmod (CPAN) Perl modules: preparing a new module for distribution

perlutil (CPAN) utilities packaged with the Perl distribution

perlcompile (CPAN) Perl compiler suite intro

perlfilter (CPAN) Perl source filters

Internals and C Language Interface

perlembed (CPAN) Perl ways to embed perl in your C or C++ application
perldebguts (CPAN) Perl debugging guts and tips
perlxstut (CPAN) Perl XS tutorial
perlxs (CPAN) Perl XS application programming interface
perlclib (CPAN) Internal replacements for standard C library functions
perlguts (CPAN) Perl internal functions for those doing extensions
perlcall (CPAN) Perl calling conventions from C

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

perlhack (CPAN) Perl hackers guide

Miscellaneous

perlbook (CPAN) Perl book information
perltodo (CPAN) Perl things to do

perldoc (CPAN) Look up Perl documentation in Pod format

perlhist (CPAN) Perl history records
perldelta (CPAN) Perl changes since previous version
perl587delta (CPAN) Perl changes in version 5.8.7
perl586delta (CPAN) Perl changes in version 5.8.6
perl585delta (CPAN) Perl changes in version 5.8.5
perl584delta (CPAN) Perl changes in version 5.8.4
perl583delta (CPAN) Perl changes in version 5.8.3
perl582delta (CPAN) Perl changes in version 5.8.2
perl581delta (CPAN) Perl changes in version 5.8.1
perl58delta (CPAN) Perl changes in version 5.8.0
perl573delta (CPAN) Perl changes in version 5.7.3
perl572delta (CPAN) Perl changes in version 5.7.2
perl571delta (CPAN) Perl changes in version 5.7.1
perl570delta (CPAN) Perl changes in version 5.7.0
perl561delta (CPAN) Perl changes in version 5.6.1
perl56delta (CPAN) Perl changes in version 5.6
perl5005delta (CPAN) Perl changes in version 5.005
perl5004delta (CPAN) Perl changes in version 5.004

perlartistic (CPAN) Perl Artistic License
perlgpl (CPAN) GNU General Public License

Language-Specific

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

Platform-Specific

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

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

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.