NAME
perl - Practical Extraction and Report Language
SYNOPSIS
perl [ -sTuU ] [ -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 ]...
For ease of access, the Perl manual has been split up into several sections:
perl Perl overview (this section)
perlfaq Perl frequently asked questions
perltoc Perl documentation table of contents
perlbook Perl book information
perlsyn Perl syntax
perldata Perl data structures
perlop Perl operators and precedence
perlsub Perl subroutines
perlfunc Perl builtin functions
perlreftut Perl references short introduction
perldsc Perl data structures intro
perlrequick Perl regular expressions quick start
perlpod Perl plain old documentation
perlstyle Perl style guide
perltrap Perl traps for the unwary
perlrun Perl execution and options
perldiag Perl diagnostic messages
perllexwarn Perl warnings and their control
perldebtut Perl debugging tutorial
perldebug Perl debugging
perlvar Perl predefined variables
perllol Perl data structures: arrays of arrays
perlopentut Perl open() tutorial
perlretut Perl regular expressions tutorial
perlre Perl regular expressions, the rest of the story
perlref Perl references, the rest of the story
perlform Perl formats
perlboot Perl OO tutorial for beginners
perltoot Perl OO tutorial, part 1
perltootc Perl OO tutorial, part 2
perlobj Perl objects
perlbot Perl OO tricks and examples
perltie Perl objects hidden behind simple variables
perlipc Perl interprocess communication
perlfork Perl fork() information
perlnumber Perl number semantics
perlthrtut Perl threads tutorial
perlport Perl portability guide
perllocale Perl locale support
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
perlmodinstall Perl modules: how to install from CPAN
perlnewmod Perl modules: preparing a new module for distribution
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
perlcompile Perl compiler suite intro
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
perlguts Perl internal functions for those doing extensions
perlcall Perl calling conventions from C
perlutil utilities packaged with the Perl distribution
perlfilter Perl source filters
perldbmfilter Perl DBM filters
perlapi Perl API listing (autogenerated)
perlintern Perl internal functions (autogenerated)
perlapio Perl internal IO abstraction interface
perltodo Perl things to do
perlhack Perl hackers guide
perlhist Perl history records
perldelta Perl changes since previous version
perl5005delta Perl changes in version 5.005
perl5004delta Perl changes in version 5.004
perlaix Perl notes for AIX
perlamiga Perl notes for Amiga
perlcygwin Perl notes for Cygwin
perldos Perl notes for DOS
perlepoc Perl notes for EPOC
perlhpux Perl notes for HP-UX
perlmachten Perl notes for Power MachTen
perlmpeix Perl notes for MPE/iX
perlos2 Perl notes for OS/2
perlos390 Perl notes for OS/390
perlposix-bc Perl notes for POSIX-BC
perlsolaris Perl notes for Solaris
perlvms Perl notes for VMS
perlvos Perl notes for Stratus VOS
perlwin32 Perl notes for Windows(If you're intending to read these straight through for the first time, the suggested order will tend to reduce the number of forward references.)
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.dirIf 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:
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
compilability into C code or Perl bytecode
Described in B and B::Bytecode.
support for light-weight processes (threads)
Described in perlthrtut and Thread.
support for internationalization, localization, and Unicode
Described in perllocale and utf8.
lexical scoping
Described in perlsub.
regular expression enhancements
enhanced debugger and interactive Perl environment, with integrated editor support
Described in perldebug.
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
"@INC" locations of perl librariesSEE ALSO
a2p awk to perl translator
s2p sed to perl translator
http://www.perl.com/ the Perl Home Page
http://www.perl.com/CPAN the Comprehensive Perl ArchiveDIAGNOSTICS
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.