=head1 SYNOPSIS
-For ease of access, the Perl manual has been split up into a number
-of sections:
-
- perl Perl overview (this section)
- perltoc Perl documentation table of contents
- perldata Perl data structures
- perlsyn Perl syntax
- perlop Perl operators and precedence
- perlre Perl regular expressions
- perlrun Perl execution and options
- perlfunc Perl builtin functions
- perlvar Perl predefined variables
- perlsub Perl subroutines
- perlmod Perl modules
- perlref Perl references
- perldsc Perl data structures intro
- perllol Perl data structures: lists of lists
- perlobj Perl objects
- perltie Perl objects hidden behind simple variables
- perlbot Perl OO tricks and examples
- perldebug Perl debugging
- perldiag Perl diagnostic messages
- perlform Perl formats
- perlipc Perl interprocess communication
- perlsec Perl security
- perltrap Perl traps for the unwary
- perlstyle Perl style guide
- perlxs Perl XS application programming interface
- perlxstut Perl XS tutorial
- perlguts Perl internal functions for those doing extensions
- perlcall Perl calling conventions from C
- perlembed Perl how to embed perl in your C or C++ app
- perlpod Perl plain old documentation
- perlbook Perl book information
+B<perl> S<[ B<-sTuU> ]> S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
+ S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>
+ S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>
+ S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]>
+ S<[ B<-P> ]> S<[ B<-S> ]> S<[ B<-x>[I<dir>] ]>
+ S<[ B<-i>[I<extension>] ]> S<[ B<-e> I<'command'> ]
+ [ B<--> ] [ I<programfile> ] [ I<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
+ perlclib Internal replacements for standard C library functions
+ 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)
+ perliol C API for Perl's implementation of IO in Layers
+ 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
+ perl56delta Perl changes in version 5.6
+ perl5005delta Perl changes in version 5.005
+ perl5004delta Perl changes in version 5.004
+
+ perlaix Perl notes for AIX
+ perlamiga Perl notes for Amiga
+ perlbs2000 Perl notes for POSIX-BC BS2000
+ 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
+ perlsolaris Perl notes for Solaris
+ perlvmesa Perl notes for VM/ESA
+ 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.)
-Additional documentation for Perl modules is available in the
-F</usr/local/man/> directory. Some of this is distributed standard with
-Perl, but you'll also find third-party modules there. You should be able
-to view this with your man(1) program by including the proper directories
-in the appropriate start-up files. To find out where these are, type:
+By default, the manpages listed above are installed in the
+F</usr/local/man/> directory.
- perl -le 'use Config; print "@Config{man1dir,man3dir}"'
+Extensive additional documentation for Perl modules is available. The
+default configuration for perl will place this additional documentation
+in the F</usr/local/lib/perl5/man> directory (or else in the F<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.
-If the directories were F</usr/local/man/man1> and F</usr/local/man/man3>,
-you would only need to add F</usr/local/man> to your MANPATH. If
-they are different, you'll have to add both stems.
+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 F</usr/local/man/man1>
+and F</usr/local/man/man3>, you need only to add that stem
+(F</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 F<perldoc> script to view module information. You might
=head1 DESCRIPTION
-Perl is an interpreted language optimized for scanning arbitrary
+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). It combines (in the author's opinion, anyway) some
-of the best features of C, B<sed>, B<awk>, and B<sh>, so people
-familiar with those languages should have little difficulty with it.
-(Language historians will also note some vestiges of B<csh>, Pascal,
-and even BASIC-PLUS.) Expression syntax corresponds quite closely to C
+elegant, minimal).
+
+Perl combines (in the author's opinion, anyway) some of the best
+features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
+those languages should have little difficulty with it. (Language
+historians will also note some vestiges of B<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 hash tables used by associative arrays
-grow as necessary to prevent degraded performance. Perl uses
-sophisticated pattern matching techniques to scan large amounts of data
-very quickly. Although optimized for scanning text, Perl can also
-deal with binary data, and can make dbm files look like associative
-arrays (where dbm is available). Setuid Perl scripts are safer than
-C programs through a dataflow tracing mechanism which prevents many
-stupid security holes. If you have a problem that would ordinarily use
-B<sed> or B<awk> or B<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
-B<sed> and B<awk> scripts into Perl scripts.
+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 B<sed> or B<awk> or
+B<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 B<sed> and B<awk>
+scripts into Perl scripts.
But wait, there's more...
-Perl version 5 is nearly a complete rewrite, and provides
-the following additional benefits:
+Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a complete
+rewrite that provides the following additional benefits:
-=over 5
+=over 4
-=item * Many usability enhancements
+=item *
-It is now possible to write much more readable Perl code (even within
-regular expressions). Formerly cryptic variable names can be replaced
-by mnemonic identifiers. Error messages are more informative, and the
-optional warnings will catch many of the mistakes a novice might make.
-This cannot be stressed enough. Whenever you get mysterious behavior,
-try the B<-w> switch!!! Whenever you don't get mysterious behavior,
-try using B<-w> anyway.
+modularity and reusability using innumerable modules
-=item * Simplified grammar
+Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
-The new yacc grammar is one half the size of the old one. Many of the
-arbitrary grammar rules have been regularized. The number of reserved
-words has been cut by 2/3. Despite this, nearly all old Perl scripts
-will continue to work unchanged.
+=item *
-=item * Lexical scoping
+embeddable and extensible
-Perl variables may now be declared within a lexical scope, like "auto"
-variables in C. Not only is this more efficient, but it contributes
-to better privacy for "programming in the large".
+Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,
+L<perlguts>, and L<xsubpp>.
-=item * Arbitrarily nested data structures
+=item *
-Any scalar value, including any array element, may now contain a
-reference to any other variable or subroutine. You can easily create
-anonymous variables and subroutines. Perl manages your reference
-counts for you.
+roll-your-own magic variables (including multiple simultaneous DBM implementations)
-=item * Modularity and reusability
+Described in L<perltie> and L<AnyDBM_File>.
-The Perl library is now defined in terms of modules which can be easily
-shared among various packages. A package may choose to import all or a
-portion of a module's published interface. Pragmas (that is, compiler
-directives) are defined and used by the same mechanism.
+=item *
-=item * Object-oriented programming
+subroutines can now be overridden, autoloaded, and prototyped
-A package can function as a class. Dynamic multiple inheritance and
-virtual methods are supported in a straightforward manner and with very
-little new syntax. Filehandles may now be treated as objects.
+Described in L<perlsub>.
-=item * Embeddible and Extensible
+=item *
-Perl may now be embedded easily in your C or C++ application, and can
-either call or be called by your routines through a documented
-interface. The XS preprocessor is provided to make it easy to glue
-your C or C++ routines into Perl. Dynamic loading of modules is
-supported.
+arbitrarily nested data structures and anonymous functions
-=item * POSIX compliant
+Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
-A major new module is the POSIX module, which provides access to all
-available POSIX routines and definitions, via object classes where
-appropriate.
+=item *
-=item * Package constructors and destructors
+object-oriented programming
-The new BEGIN and END blocks provide means to capture control as
-a package is being compiled, and after the program exits. As a
-degenerate case they work just like awk's BEGIN and END when you
-use the B<-p> or B<-n> switches.
+Described in L<perlobj>, L<perltoot>, and L<perlbot>.
-=item * Multiple simultaneous DBM implementations
+=item *
-A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
-files from the same script simultaneously. In fact, the old dbmopen
-interface has been generalized to allow any variable to be tied
-to an object class which defines its access methods.
+compilability into C code or Perl bytecode
-=item * Subroutine definitions may now be autoloaded
+Described in L<B> and L<B::Bytecode>.
-In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
-semantics for undefined subroutine calls. It's not just for autoloading.
+=item *
-=item * Regular expression enhancements
+support for light-weight processes (threads)
-You can now specify non-greedy quantifiers. You can now do grouping
-without creating a backreference. You can now write regular expressions
-with embedded whitespace and comments for readability. A consistent
-extensibility mechanism has been added that is upwardly compatible with
-all old regular expressions.
+Described in L<perlthrtut> and L<Thread>.
-=back
+=item *
-Ok, that's I<definitely> enough hype.
+support for internationalization, localization, and Unicode
-=head1 ENVIRONMENT
+Described in L<perllocale> and L<utf8>.
-=over 12
+=item *
-=item HOME
+lexical scoping
-Used if chdir has no argument.
+Described in L<perlsub>.
-=item LOGDIR
+=item *
-Used if chdir has no argument and HOME is not set.
+regular expression enhancements
-=item PATH
+Described in L<perlre>, with additional examples in L<perlop>.
-Used in executing subprocesses, and in finding the script if B<-S> is
-used.
+=item *
-=item PERL5LIB
+enhanced debugger and interactive Perl environment,
+with integrated editor support
-A colon-separated list of directories in which to look for Perl library
-files before looking in the standard library and the current
-directory. If PERL5LIB is not defined, PERLLIB is used. When running
-taint checks (because the script was running setuid or setgid, or the
-B<-T> switch was used), neither variable is used. The script should
-instead say
+Described in L<perldebug>.
- use lib "/my/directory";
+=item *
-=item PERL5DB
+POSIX 1003.1 compliant library
-The command used to get the debugger code. If unset, uses
+Described in L<POSIX>.
- BEGIN { require 'perl5db.pl' }
+=back
-=item PERLLIB
+Okay, that's I<definitely> enough hype.
-A colon-separated list of directories in which to look for Perl library
-files before looking in the standard library and the current
-directory. If PERL5LIB is defined, PERLLIB is not used.
+=head1 AVAILABILITY
-=back
+Perl is available for most operating systems, including virtually
+all Unix-like platforms. See L<perlport/"Supported Platforms">
+for a listing.
-Apart from these, Perl uses no other environment variables, except
-to make them available to the script being executed, and to child
-processes. However, scripts running setuid would do well to execute
-the following lines before doing anything else, just to keep people
-honest:
+=head1 ENVIRONMENT
- $ENV{'PATH'} = '/bin:/usr/bin'; # or whatever you need
- $ENV{'SHELL'} = '/bin/sh' if defined $ENV{'SHELL'};
- $ENV{'IFS'} = '' if defined $ENV{'IFS'};
+See L<perlrun>.
=head1 AUTHOR
-Larry Wall E<lt><F<lwall@netlabs.com>E<gt>, with the help of oodles of other folks.
+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 .
=head1 FILES
- "/tmp/perl-e$$" temporary file for -e commands
- "@INC" locations of perl 5 libraries
+ "@INC" locations of perl libraries
=head1 SEE 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 Archive
+
=head1 DIAGNOSTICS
-The B<-w> switch produces some lovely diagnostics.
+The C<use warnings> pragma (and the B<-w> switch) produces some
+lovely diagnostics.
-See L<perldiag> for explanations of all Perl's diagnostics.
+See L<perldiag> for explanations of all Perl's diagnostics. The C<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 the case of a script passed to Perl via B<-e> switches, each
+(In a script passed to Perl via B<-e> switches, each
B<-e> is counted as one line.)
Setuid scripts have additional constraints that can produce error
The B<-w> switch is not mandatory.
Perl is at the mercy of your machine's definitions of various
-operations such as type casting, atof() and sprintf(). The latter
-can even trigger a coredump when passed ludicrous input values.
+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()
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 identifier may not be longer than 255 characters, and no
-component of your PATH may be longer than 255 if you use B<-S>. A regular
-expression may not compile to more than 32767 bytes internally.
-
-See the perl bugs database at F<http://perl.com/perl/bugs/>. You may
-mail your bug reports (be sure to include full configuration information
-as output by the myconfig program in the perl source tree) to
-F<perlbug@perl.com>.
+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 C<perl -V>) to perlbug@perl.org . If you've succeeded
+in compiling perl, the B<perlbug> script in the F<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.
https://perl5.git.perl.org / perl5.git / blobdiff