perl - Practical Extraction and Report Language
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.
- perl Perl overview (this section)
- perlintro Perl introduction for beginners
- perltoc Perl documentation table of contents
- perlreftut Perl references short introduction
- perldsc Perl data structures intro
- perllol Perl data structures: arrays of arrays
- perlrequick Perl regular expressions quick start
- perlretut Perl regular expressions tutorial
- perlboot Perl OO tutorial for beginners
- 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
- 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
- perlrebackslash Perl regular expression backslash sequences
- perlrecharclass Perl regular expression character classes
- 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
- perlunifaq Perl Unicode FAQ
- perlunitut Perl Unicode tutorial
- 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
- perlglossary Perl Glossary
- 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
- perlreguts Perl regular expression engine internals
- 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
- perlbook Perl book information
- perlcommunity Perl community information
- perltodo Perl things to do
- perldoc Look up Perl documentation in Pod format
- perlhist Perl history records
- perldelta Perl changes since previous version
- perl588delta Perl changes in version 5.8.8
- perl587delta Perl changes in version 5.8.7
- perl586delta Perl changes in version 5.8.6
- perl585delta Perl changes in version 5.8.5
- perl584delta Perl changes in version 5.8.4
- 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
- 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)
- 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
- perllinux Perl notes for Linux
- 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
- perlopenbsd Perl notes for OpenBSD
- 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
- perlriscos Perl notes for RISC OS
- 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
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.
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:
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 perltie 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
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.
Perl is available for most operating systems, including virtually all Unix-like platforms. See Supported Platforms in perlport for a listing.
See perlrun.
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 .
- "@INC" locations of perl libraries
- a2p awk to perl translator
- s2p sed to perl translator
- http://www.perl.org/ the Perl homepage
- http://www.perl.com/ Perl articles (O'Reilly)
- http://www.cpan.org/ the Comprehensive Perl Archive
- http://www.pm.org/ the Perl Mongers
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?
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.
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.