This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Run "cd pod ; ../perl -I../lib buildtoc --build-all"
[perl5.git] / pod / perl.pod
CommitLineData
a0d0e21e
LW
1=head1 NAME
2
3perl - Practical Extraction and Report Language
4
5=head1 SYNOPSIS
6
df451b2a
RGS
7B<perl> S<[ B<-sTtuUWX> ]>
8 S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
9 S<[ B<-cw> ] [ B<-d>[B<t>][:I<debugger>] ] [ B<-D>[I<number/list>] ]>
10 S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal/hexadecimal>] ]>
11 S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ] [ B<-f> ]>
df451b2a 12 S<[ B<-C [I<number/list>] >]>
df451b2a
RGS
13 S<[ B<-S> ]>
14 S<[ B<-x>[I<dir>] ]>
15 S<[ B<-i>[I<extension>] ]>
eb1dd64e 16 S<[ [B<-e>|B<-E>] I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
c07a80fd 17
10151d09
JH
18If you're new to Perl, you should start with L<perlintro>, which is a
19general intro for beginners and provides some background to help you
20navigate the rest of Perl's extensive documentation.
21
22For ease of access, the Perl manual has been split up into several sections.
a0d0e21e 23
fd7b6849
MJD
24=head2 Overview
25
fb9cefb4 26 perl Perl overview (this section)
10151d09 27 perlintro Perl introduction for beginners
fb9cefb4 28 perltoc Perl documentation table of contents
760ac839 29
fd7b6849
MJD
30=head2 Tutorials
31
7a2320f0
AMS
32 perlreftut Perl references short introduction
33 perldsc Perl data structures intro
34 perllol Perl data structures: arrays of arrays
7a2320f0 35
41630250 36 perlrequick Perl regular expressions quick start
7a2320f0
AMS
37 perlretut Perl regular expressions tutorial
38
39 perlboot Perl OO tutorial for beginners
40 perltoot Perl OO tutorial, part 1
41 perltooc Perl OO tutorial, part 2
42 perlbot Perl OO tricks and examples
43
da096611
RGS
44 perlperf Perl Performance and Optimization Techniques
45
7a2320f0
AMS
46 perlstyle Perl style guide
47
41630250 48 perlcheat Perl cheat sheet
7a2320f0
AMS
49 perltrap Perl traps for the unwary
50 perldebtut Perl debugging tutorial
51
fd7b6849
MJD
52 perlfaq Perl frequently asked questions
53 perlfaq1 General Questions About Perl
54 perlfaq2 Obtaining and Learning about Perl
55 perlfaq3 Programming Tools
56 perlfaq4 Data Manipulation
57 perlfaq5 Files and Formats
58 perlfaq6 Regexes
59 perlfaq7 Perl Language Issues
60 perlfaq8 System Interaction
61 perlfaq9 Networking
0f542199 62
fd7b6849 63=head2 Reference Manual
413510b3 64
fb9cefb4 65 perlsyn Perl syntax
4755096e 66 perldata Perl data structures
fb9cefb4 67 perlop Perl operators and precedence
c2e66d9e 68 perlsub Perl subroutines
fd7b6849 69 perlfunc Perl built-in functions
413510b3 70 perlopentut Perl open() tutorial
41630250 71 perlpacktut Perl pack() and unpack() tutorial
c2e66d9e 72 perlpod Perl plain old documentation
41630250 73 perlpodspec Perl plain old documentation format specification
c2e66d9e
GS
74 perlrun Perl execution and options
75 perldiag Perl diagnostic messages
41630250 76 perllexwarn Perl warnings and their control
4755096e 77 perldebug Perl debugging
fb9cefb4 78 perlvar Perl predefined variables
4755096e 79 perlre Perl regular expressions, the rest of the story
8a118206
RGS
80 perlrebackslash Perl regular expression backslash sequences
81 perlrecharclass Perl regular expression character classes
30487ceb 82 perlreref Perl regular expressions quick reference
d396a558 83 perlref Perl references, the rest of the story
fb9cefb4 84 perlform Perl formats
d396a558 85 perlobj Perl objects
d396a558 86 perltie Perl objects hidden behind simple variables
fd7b6849 87 perldbmfilter Perl DBM filters
760ac839 88
c2e66d9e
GS
89 perlipc Perl interprocess communication
90 perlfork Perl fork() information
91 perlnumber Perl number semantics
53d7eaa8 92
c2e66d9e
GS
93 perlthrtut Perl threads tutorial
94
95 perlport Perl portability guide
d396a558 96 perllocale Perl locale support
07fcf8ff 97 perluniintro Perl Unicode introduction
41630250 98 perlunicode Perl Unicode support
3426ea3d 99 perlunifaq Perl Unicode FAQ
aadaa455 100 perlunitut Perl Unicode tutorial
d396a558 101 perlebcdic Considerations for running Perl on EBCDIC platforms
c2e66d9e 102
d396a558 103 perlsec Perl security
4755096e 104
c2e66d9e 105 perlmod Perl modules: how they work
35bf961c
JH
106 perlmodlib Perl modules: how to write and use
107 perlmodstyle Perl modules: how to write modules with style
fd7b6849 108 perlmodinstall Perl modules: how to install from CPAN
c2e66d9e 109 perlnewmod Perl modules: preparing a new module for distribution
a550ee30 110 perlpragma Perl modules: writing a user pragma
760ac839 111
fd7b6849 112 perlutil utilities packaged with the Perl distribution
760ac839 113
41630250 114 perlcompile Perl compiler suite intro
760ac839 115
fd7b6849
MJD
116 perlfilter Perl source filters
117
97a1d740
YST
118 perlglossary Perl Glossary
119
fd7b6849
MJD
120=head2 Internals and C Language Interface
121
fb9cefb4 122 perlembed Perl ways to embed perl in your C or C++ application
41630250 123 perldebguts Perl debugging guts and tips
fb9cefb4 124 perlxstut Perl XS tutorial
4755096e 125 perlxs Perl XS application programming interface
f40a6c71 126 perlclib Internal replacements for standard C library functions
fb9cefb4
GS
127 perlguts Perl internal functions for those doing extensions
128 perlcall Perl calling conventions from C
15932acc 129 perlmroapi Perl method resolution plugin interface
108003db 130 perlreapi Perl regular expression plugin interface
b23a565d 131 perlreguts Perl regular expression engine internals
fd7b6849 132
954c1994
GS
133 perlapi Perl API listing (autogenerated)
134 perlintern Perl internal functions (autogenerated)
dc5c060f 135 perliol C API for Perl's implementation of IO in Layers
4755096e 136 perlapio Perl internal IO abstraction interface
fd7b6849 137
e8cd7eae 138 perlhack Perl hackers guide
00f54a07 139 perlrepository Perl source repository
4755096e 140
fd7b6849
MJD
141=head2 Miscellaneous
142
143 perlbook Perl book information
cbd87e7e 144 perlcommunity Perl community information
fd7b6849
MJD
145 perltodo Perl things to do
146
2a551100
JH
147 perldoc Look up Perl documentation in Pod format
148
fb9cefb4 149 perlhist Perl history records
4755096e 150 perldelta Perl changes since previous version
11545435 151 perl5110delta Perl changes in version 5.11.0
7cdf958d 152 perl5101delta Perl changes in version 5.10.1
7120b314 153 perl5100delta Perl changes in version 5.10.0
cf6c151c 154 perl595delta Perl changes in version 5.9.5
f6eae373 155 perl594delta Perl changes in version 5.9.4
6c7deadb 156 perl593delta Perl changes in version 5.9.3
496c75d0 157 perl592delta Perl changes in version 5.9.2
e0eb806d 158 perl591delta Perl changes in version 5.9.1
1400179b 159 perl590delta Perl changes in version 5.9.0
fc5be808 160 perl589delta Perl changes in version 5.8.9
c11a53c6 161 perl588delta Perl changes in version 5.8.8
315ba985 162 perl587delta Perl changes in version 5.8.7
e4bb216d 163 perl586delta Perl changes in version 5.8.6
07e9b5fe 164 perl585delta Perl changes in version 5.8.5
5f15c94e 165 perl584delta Perl changes in version 5.8.4
2e038148
NC
166 perl583delta Perl changes in version 5.8.3
167 perl582delta Perl changes in version 5.8.2
b6235c4f 168 perl581delta Perl changes in version 5.8.1
2e038148 169 perl58delta Perl changes in version 5.8.0
77b096b5 170 perl573delta Perl changes in version 5.7.3
245d750e 171 perl572delta Perl changes in version 5.7.2
1db9e106
JH
172 perl571delta Perl changes in version 5.7.1
173 perl570delta Perl changes in version 5.7.0
493a87da 174 perl561delta Perl changes in version 5.6.1
41630250 175 perl56delta Perl changes in version 5.6
4755096e
GS
176 perl5005delta Perl changes in version 5.005
177 perl5004delta Perl changes in version 5.004
d516a115 178
2a551100
JH
179 perlartistic Perl Artistic License
180 perlgpl GNU General Public License
181
d8416318
JH
182=head2 Language-Specific
183
184 perlcn Perl for Simplified Chinese (in EUC-CN)
185 perljp Perl for Japanese (in EUC-JP)
186 perlko Perl for Korean (in EUC-KR)
187 perltw Perl for Traditional Chinese (in Big5)
188
fd7b6849
MJD
189=head2 Platform-Specific
190
37d4d706 191 perlaix Perl notes for AIX
a83b6f46
JH
192 perlamiga Perl notes for AmigaOS
193 perlapollo Perl notes for Apollo DomainOS
194 perlbeos Perl notes for BeOS
dc5c060f 195 perlbs2000 Perl notes for POSIX-BC BS2000
a1f19229 196 perlce Perl notes for WinCE
49877630 197 perlcygwin Perl notes for Cygwin
245d750e 198 perldgux Perl notes for DG/UX
49877630 199 perldos Perl notes for DOS
9a997319 200 perlepoc Perl notes for EPOC
41630250 201 perlfreebsd Perl notes for FreeBSD
f6706af3 202 perlhaiku Perl notes for Haiku
49877630 203 perlhpux Perl notes for HP-UX
a83b6f46 204 perlhurd Perl notes for Hurd
469e7be4 205 perlirix Perl notes for Irix
991e8403 206 perllinux Perl notes for Linux
26d9b02f 207 perlmacos Perl notes for Mac OS (Classic)
0d53b15f 208 perlmacosx Perl notes for Mac OS X
ab648d5e 209 perlmpeix Perl notes for MPE/iX
41630250 210 perlnetware Perl notes for NetWare
b0846812 211 perlopenbsd Perl notes for OpenBSD
49877630
GS
212 perlos2 Perl notes for OS/2
213 perlos390 Perl notes for OS/390
522b859a 214 perlos400 Perl notes for OS/400
a83b6f46
JH
215 perlplan9 Perl notes for Plan 9
216 perlqnx Perl notes for QNX
2f08ed66 217 perlriscos Perl notes for RISC OS
d420ca49 218 perlsolaris Perl notes for Solaris
27da23d5 219 perlsymbian Perl notes for Symbian
772ff3b9 220 perltru64 Perl notes for Tru64
41630250 221 perluts Perl notes for UTS
cbe1151c 222 perlvmesa Perl notes for VM/ESA
49877630 223 perlvms Perl notes for VMS
9a997319 224 perlvos Perl notes for Stratus VOS
49877630
GS
225 perlwin32 Perl notes for Windows
226
a0d0e21e 227
19799a22 228By default, the manpages listed above are installed in the
fc952dec
CS
229F</usr/local/man/> directory.
230
231Extensive additional documentation for Perl modules is available. The
232default configuration for perl will place this additional documentation
233in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
234subdirectory of the Perl library directory). Some of this additional
235documentation is distributed standard with Perl, but you'll also find
236documentation for third-party modules there.
237
238You should be able to view Perl's documentation with your man(1)
239program by including the proper directories in the appropriate start-up
240files, or in the MANPATH environment variable. To find out where the
241configuration has installed the manpages, type:
16d20bd9 242
760ac839 243 perl -V:man.dir
16d20bd9 244
fc952dec
CS
245If the directories have a common stem, such as F</usr/local/man/man1>
246and F</usr/local/man/man3>, you need only to add that stem
247(F</usr/local/man>) to your man(1) configuration files or your MANPATH
248environment variable. If they do not share a stem, you'll have to add
249both stems.
16d20bd9
AD
250
251If that doesn't work for some reason, you can still use the
4633a7c4
LW
252supplied F<perldoc> script to view module information. You might
253also look into getting a replacement man program.
16d20bd9 254
a0d0e21e
LW
255If something strange has gone wrong with your program and you're not
256sure where you should look for help, try the B<-w> switch first. It
257will often point out exactly where the trouble is.
258
259=head1 DESCRIPTION
260
5f05dabc 261Perl is a language optimized for scanning arbitrary
a0d0e21e
LW
262text files, extracting information from those text files, and printing
263reports based on that information. It's also a good language for many
264system management tasks. The language is intended to be practical
265(easy to use, efficient, complete) rather than beautiful (tiny,
94d58c47
PP
266elegant, minimal).
267
aa689395
PP
268Perl combines (in the author's opinion, anyway) some of the best
269features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
270those languages should have little difficulty with it. (Language
271historians will also note some vestiges of B<csh>, Pascal, and even
14218588 272BASIC-PLUS.) Expression syntax corresponds closely to C
a0d0e21e
LW
273expression syntax. Unlike most Unix utilities, Perl does not
274arbitrarily limit the size of your data--if you've got the memory,
aa689395 275Perl can slurp in your whole file as a single string. Recursion is of
0f31cffe 276unlimited depth. And the tables used by hashes (sometimes called
aa689395 277"associative arrays") grow as necessary to prevent degraded
0f31cffe 278performance. Perl can use sophisticated pattern matching techniques to
14218588 279scan large amounts of data quickly. Although optimized for
aa689395
PP
280scanning text, Perl can also deal with binary data, and can make dbm
281files look like hashes. Setuid Perl scripts are safer than C programs
14218588 282through a dataflow tracing mechanism that prevents many stupid
aa689395
PP
283security holes.
284
285If you have a problem that would ordinarily use B<sed> or B<awk> or
286B<sh>, but it exceeds their capabilities or must run a little faster,
287and you don't want to write the silly thing in C, then Perl may be for
288you. There are also translators to turn your B<sed> and B<awk>
289scripts into Perl scripts.
a0d0e21e
LW
290
291But wait, there's more...
292
19799a22
GS
293Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a complete
294rewrite that provides the following additional benefits:
a0d0e21e 295
13a2d996 296=over 4
a0d0e21e 297
551e1d92
RB
298=item *
299
300modularity and reusability using innumerable modules
a0d0e21e 301
19799a22 302Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
a0d0e21e 303
551e1d92
RB
304=item *
305
306embeddable and extensible
a0d0e21e 307
19799a22
GS
308Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,
309L<perlguts>, and L<xsubpp>.
a0d0e21e 310
551e1d92
RB
311=item *
312
63de3cb2
JH
313roll-your-own magic variables (including multiple simultaneous DBM
314implementations)
a0d0e21e 315
19799a22 316Described in L<perltie> and L<AnyDBM_File>.
a0d0e21e 317
551e1d92
RB
318=item *
319
320subroutines can now be overridden, autoloaded, and prototyped
a0d0e21e 321
19799a22 322Described in L<perlsub>.
a0d0e21e 323
551e1d92
RB
324=item *
325
326arbitrarily nested data structures and anonymous functions
a0d0e21e 327
19799a22 328Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
a0d0e21e 329
551e1d92
RB
330=item *
331
332object-oriented programming
a0d0e21e 333
f6b3c421
MJD
334Described in L<perlobj>, L<perlboot>, L<perltoot>, L<perltooc>,
335and L<perlbot>.
a0d0e21e 336
551e1d92
RB
337=item *
338
551e1d92 339support for light-weight processes (threads)
a0d0e21e 340
63de3cb2 341Described in L<perlthrtut> and L<threads>.
a0d0e21e 342
551e1d92
RB
343=item *
344
63de3cb2 345support for Unicode, internationalization, and localization
a0d0e21e 346
63de3cb2 347Described in L<perluniintro>, L<perllocale> and L<Locale::Maketext>.
a0d0e21e 348
551e1d92
RB
349=item *
350
351lexical scoping
a0d0e21e 352
19799a22 353Described in L<perlsub>.
a0d0e21e 354
551e1d92
RB
355=item *
356
357regular expression enhancements
a0d0e21e 358
19799a22 359Described in L<perlre>, with additional examples in L<perlop>.
a0d0e21e 360
551e1d92
RB
361=item *
362
363enhanced debugger and interactive Perl environment,
364with integrated editor support
a0d0e21e 365
f6b3c421 366Described in L<perldebtut>, L<perldebug> and L<perldebguts>.
a0d0e21e 367
551e1d92
RB
368=item *
369
370POSIX 1003.1 compliant library
5f05dabc 371
19799a22 372Described in L<POSIX>.
5f05dabc 373
a0d0e21e
LW
374=back
375
68dc0745 376Okay, that's I<definitely> enough hype.
a0d0e21e 377
8e465e4e
JH
378=head1 AVAILABILITY
379
14218588 380Perl is available for most operating systems, including virtually
055fd3a9
GS
381all Unix-like platforms. See L<perlport/"Supported Platforms">
382for a listing.
8bc4a6bb 383
a0d0e21e
LW
384=head1 ENVIRONMENT
385
1e422769 386See L<perlrun>.
a0d0e21e
LW
387
388=head1 AUTHOR
389
19799a22 390Larry Wall <larry@wall.org>, with the help of oodles of other folks.
a0d0e21e 391
a99b1639
TP
392If your Perl success stories and testimonials may be of help to others
393who wish to advocate the use of Perl in their applications,
394or if you wish to simply express your gratitude to Larry and the
19799a22 395Perl developers, please write to perl-thanks@perl.org .
a99b1639 396
a0d0e21e
LW
397=head1 FILES
398
5f05dabc 399 "@INC" locations of perl libraries
a0d0e21e
LW
400
401=head1 SEE ALSO
402
403 a2p awk to perl translator
404 s2p sed to perl translator
405
c5f69108 406 http://www.perl.org/ the Perl homepage
da9e6348 407 http://www.perl.com/ Perl articles (O'Reilly)
f6b3c421 408 http://www.cpan.org/ the Comprehensive Perl Archive
c5f69108 409 http://www.pm.org/ the Perl Mongers
19799a22 410
a0d0e21e
LW
411=head1 DIAGNOSTICS
412
9f1b1f2d
GS
413The C<use warnings> pragma (and the B<-w> switch) produces some
414lovely diagnostics.
a0d0e21e 415
5a964f20
TC
416See L<perldiag> for explanations of all Perl's diagnostics. The C<use
417diagnostics> pragma automatically turns Perl's normally terse warnings
418and errors into these longer forms.
a0d0e21e
LW
419
420Compilation errors will tell you the line number of the error, with an
421indication of the next token or token type that was to be examined.
14218588 422(In a script passed to Perl via B<-e> switches, each
a0d0e21e
LW
423B<-e> is counted as one line.)
424
425Setuid scripts have additional constraints that can produce error
426messages such as "Insecure dependency". See L<perlsec>.
427
428Did we mention that you should definitely consider using the B<-w>
429switch?
430
431=head1 BUGS
432
433The B<-w> switch is not mandatory.
434
435Perl is at the mercy of your machine's definitions of various
1b3f7d21
CS
436operations such as type casting, atof(), and floating-point
437output with sprintf().
a0d0e21e 438
748a9306 439If your stdio requires a seek or eof between reads and writes on a
a0d0e21e
LW
440particular stream, so does Perl. (This doesn't apply to sysread()
441and syswrite().)
442
443While none of the built-in data types have any arbitrary size limits
444(apart from memory size), there are still a few arbitrary limits: a
a30ac152
GS
445given variable name may not be longer than 251 characters. Line numbers
446displayed by diagnostics are internally stored as short integers,
447so they are limited to a maximum of 65535 (higher numbers usually being
448affected by wraparound).
a0d0e21e 449
b0607b7a 450You may mail your bug reports (be sure to include full configuration
19799a22 451information as output by the myconfig program in the perl source
7f2de2d2 452tree, or by C<perl -V>) to perlbug@perl.org . If you've succeeded
055fd3a9 453in compiling perl, the B<perlbug> script in the F<utils/> subdirectory
19799a22 454can be used to help mail in a bug report.
4633a7c4 455
a0d0e21e
LW
456Perl actually stands for Pathologically Eclectic Rubbish Lister, but
457don't tell anyone I said that.
458
459=head1 NOTES
460
461The Perl motto is "There's more than one way to do it." Divining
462how many more is left as an exercise to the reader.
463
4633a7c4 464The three principal virtues of a programmer are Laziness,
a0d0e21e 465Impatience, and Hubris. See the Camel Book for why.
16d20bd9 466