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a0d0e21e LW |
1 | =head1 NAME |
2 | ||
3 | perl - Practical Extraction and Report Language | |
4 | ||
5 | =head1 SYNOPSIS | |
6 | ||
94d58c47 | 7 | B<perl> S<[ B<-sTuU> ]> |
8 | S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]> | |
9 | S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]> | |
10 | S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]> | |
11 | S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]> | |
12 | S<[ B<-P> ]> | |
13 | S<[ B<-S> ]> | |
14 | S<[ B<-x>[I<dir>] ]> | |
15 | S<[ B<-i>[I<extension>] ]> | |
16 | S<[ B<-e> I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...> | |
c07a80fd | 17 | |
a0d0e21e LW |
18 | For ease of access, the Perl manual has been split up into a number |
19 | of sections: | |
20 | ||
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21 | perl Perl overview (this section) |
22 | perldelta Perl changes since previous version | |
9bc80687 GS |
23 | perl5005delta Perl changes in version 5.005 |
24 | perl5004delta Perl changes in version 5.004 | |
fb9cefb4 GS |
25 | perlfaq Perl frequently asked questions |
26 | perltoc Perl documentation table of contents | |
760ac839 | 27 | |
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28 | perldata Perl data structures |
29 | perlsyn Perl syntax | |
30 | perlop Perl operators and precedence | |
31 | perlre Perl regular expressions | |
32 | perlrun Perl execution and options | |
33 | perlfunc Perl builtin functions | |
2605996a | 34 | perlopentut Perl open() tutorial |
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35 | perlvar Perl predefined variables |
36 | perlsub Perl subroutines | |
f8284313 | 37 | perlopentut Perl opening things tutorial |
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38 | perlmod Perl modules: how they work |
39 | perlmodlib Perl modules: how to write and use | |
40 | perlmodinstall Perl modules: how to install from CPAN | |
41 | perlform Perl formats | |
42 | perllocale Perl locale support | |
760ac839 | 43 | |
fb9cefb4 | 44 | perlref Perl references |
a1e2a320 | 45 | perlreftut Perl references short introduction |
fb9cefb4 GS |
46 | perldsc Perl data structures intro |
47 | perllol Perl data structures: lists of lists | |
48 | perltoot Perl OO tutorial | |
49 | perlobj Perl objects | |
50 | perltie Perl objects hidden behind simple variables | |
51 | perlbot Perl OO tricks and examples | |
52 | perlipc Perl interprocess communication | |
2605996a | 53 | perlthrtut Perl threads tutorial |
760ac839 | 54 | |
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55 | perldebug Perl debugging |
56 | perldiag Perl diagnostic messages | |
57 | perlsec Perl security | |
58 | perltrap Perl traps for the unwary | |
59 | perlport Perl portability guide | |
60 | perlstyle Perl style guide | |
760ac839 | 61 | |
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62 | perlpod Perl plain old documentation |
63 | perlbook Perl book information | |
760ac839 | 64 | |
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65 | perlembed Perl ways to embed perl in your C or C++ application |
66 | perlapio Perl internal IO abstraction interface | |
67 | perlxs Perl XS application programming interface | |
68 | perlxstut Perl XS tutorial | |
69 | perlguts Perl internal functions for those doing extensions | |
70 | perlcall Perl calling conventions from C | |
a0d0e21e | 71 | |
fb9cefb4 | 72 | perlhist Perl history records |
d516a115 | 73 | |
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74 | (If you're intending to read these straight through for the first time, |
75 | the suggested order will tend to reduce the number of forward references.) | |
76 | ||
fc952dec CS |
77 | By default, all of the above manpages are installed in the |
78 | F</usr/local/man/> directory. | |
79 | ||
80 | Extensive additional documentation for Perl modules is available. The | |
81 | default configuration for perl will place this additional documentation | |
82 | in the F</usr/local/lib/perl5/man> directory (or else in the F<man> | |
83 | subdirectory of the Perl library directory). Some of this additional | |
84 | documentation is distributed standard with Perl, but you'll also find | |
85 | documentation for third-party modules there. | |
86 | ||
87 | You should be able to view Perl's documentation with your man(1) | |
88 | program by including the proper directories in the appropriate start-up | |
89 | files, or in the MANPATH environment variable. To find out where the | |
90 | configuration has installed the manpages, type: | |
16d20bd9 | 91 | |
760ac839 | 92 | perl -V:man.dir |
16d20bd9 | 93 | |
fc952dec CS |
94 | If the directories have a common stem, such as F</usr/local/man/man1> |
95 | and F</usr/local/man/man3>, you need only to add that stem | |
96 | (F</usr/local/man>) to your man(1) configuration files or your MANPATH | |
97 | environment variable. If they do not share a stem, you'll have to add | |
98 | both stems. | |
16d20bd9 AD |
99 | |
100 | If that doesn't work for some reason, you can still use the | |
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101 | supplied F<perldoc> script to view module information. You might |
102 | also look into getting a replacement man program. | |
16d20bd9 | 103 | |
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104 | If something strange has gone wrong with your program and you're not |
105 | sure where you should look for help, try the B<-w> switch first. It | |
106 | will often point out exactly where the trouble is. | |
107 | ||
108 | =head1 DESCRIPTION | |
109 | ||
5f05dabc | 110 | Perl is a language optimized for scanning arbitrary |
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111 | text files, extracting information from those text files, and printing |
112 | reports based on that information. It's also a good language for many | |
113 | system management tasks. The language is intended to be practical | |
114 | (easy to use, efficient, complete) rather than beautiful (tiny, | |
94d58c47 | 115 | elegant, minimal). |
116 | ||
aa689395 | 117 | Perl combines (in the author's opinion, anyway) some of the best |
118 | features of C, B<sed>, B<awk>, and B<sh>, so people familiar with | |
119 | those languages should have little difficulty with it. (Language | |
120 | historians will also note some vestiges of B<csh>, Pascal, and even | |
121 | BASIC-PLUS.) Expression syntax corresponds quite closely to C | |
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122 | expression syntax. Unlike most Unix utilities, Perl does not |
123 | arbitrarily limit the size of your data--if you've got the memory, | |
aa689395 | 124 | Perl can slurp in your whole file as a single string. Recursion is of |
0f31cffe | 125 | unlimited depth. And the tables used by hashes (sometimes called |
aa689395 | 126 | "associative arrays") grow as necessary to prevent degraded |
0f31cffe | 127 | performance. Perl can use sophisticated pattern matching techniques to |
aa689395 | 128 | scan large amounts of data very quickly. Although optimized for |
129 | scanning text, Perl can also deal with binary data, and can make dbm | |
130 | files look like hashes. Setuid Perl scripts are safer than C programs | |
131 | through a dataflow tracing mechanism which prevents many stupid | |
132 | security holes. | |
133 | ||
134 | If you have a problem that would ordinarily use B<sed> or B<awk> or | |
135 | B<sh>, but it exceeds their capabilities or must run a little faster, | |
136 | and you don't want to write the silly thing in C, then Perl may be for | |
137 | you. There are also translators to turn your B<sed> and B<awk> | |
138 | scripts into Perl scripts. | |
a0d0e21e LW |
139 | |
140 | But wait, there's more... | |
141 | ||
142 | Perl version 5 is nearly a complete rewrite, and provides | |
143 | the following additional benefits: | |
144 | ||
145 | =over 5 | |
146 | ||
147 | =item * Many usability enhancements | |
148 | ||
149 | It is now possible to write much more readable Perl code (even within | |
150 | regular expressions). Formerly cryptic variable names can be replaced | |
151 | by mnemonic identifiers. Error messages are more informative, and the | |
152 | optional warnings will catch many of the mistakes a novice might make. | |
153 | This cannot be stressed enough. Whenever you get mysterious behavior, | |
154 | try the B<-w> switch!!! Whenever you don't get mysterious behavior, | |
155 | try using B<-w> anyway. | |
156 | ||
157 | =item * Simplified grammar | |
158 | ||
159 | The new yacc grammar is one half the size of the old one. Many of the | |
160 | arbitrary grammar rules have been regularized. The number of reserved | |
161 | words has been cut by 2/3. Despite this, nearly all old Perl scripts | |
162 | will continue to work unchanged. | |
163 | ||
164 | =item * Lexical scoping | |
165 | ||
166 | Perl variables may now be declared within a lexical scope, like "auto" | |
167 | variables in C. Not only is this more efficient, but it contributes | |
fc952dec | 168 | to better privacy for "programming in the large". Anonymous |
5f05dabc | 169 | subroutines exhibit deep binding of lexical variables (closures). |
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170 | |
171 | =item * Arbitrarily nested data structures | |
172 | ||
173 | Any scalar value, including any array element, may now contain a | |
174 | reference to any other variable or subroutine. You can easily create | |
175 | anonymous variables and subroutines. Perl manages your reference | |
176 | counts for you. | |
177 | ||
178 | =item * Modularity and reusability | |
179 | ||
180 | The Perl library is now defined in terms of modules which can be easily | |
181 | shared among various packages. A package may choose to import all or a | |
182 | portion of a module's published interface. Pragmas (that is, compiler | |
183 | directives) are defined and used by the same mechanism. | |
184 | ||
185 | =item * Object-oriented programming | |
186 | ||
187 | A package can function as a class. Dynamic multiple inheritance and | |
188 | virtual methods are supported in a straightforward manner and with very | |
189 | little new syntax. Filehandles may now be treated as objects. | |
190 | ||
c07a80fd | 191 | =item * Embeddable and Extensible |
a0d0e21e LW |
192 | |
193 | Perl may now be embedded easily in your C or C++ application, and can | |
194 | either call or be called by your routines through a documented | |
195 | interface. The XS preprocessor is provided to make it easy to glue | |
196 | your C or C++ routines into Perl. Dynamic loading of modules is | |
5f05dabc | 197 | supported, and Perl itself can be made into a dynamic library. |
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198 | |
199 | =item * POSIX compliant | |
200 | ||
201 | A major new module is the POSIX module, which provides access to all | |
202 | available POSIX routines and definitions, via object classes where | |
203 | appropriate. | |
204 | ||
205 | =item * Package constructors and destructors | |
206 | ||
207 | The new BEGIN and END blocks provide means to capture control as | |
208 | a package is being compiled, and after the program exits. As a | |
209 | degenerate case they work just like awk's BEGIN and END when you | |
210 | use the B<-p> or B<-n> switches. | |
211 | ||
212 | =item * Multiple simultaneous DBM implementations | |
213 | ||
214 | A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB | |
215 | files from the same script simultaneously. In fact, the old dbmopen | |
216 | interface has been generalized to allow any variable to be tied | |
217 | to an object class which defines its access methods. | |
218 | ||
219 | =item * Subroutine definitions may now be autoloaded | |
220 | ||
221 | In fact, the AUTOLOAD mechanism also allows you to define any arbitrary | |
5f05dabc | 222 | semantics for undefined subroutine calls. It's not for just autoloading. |
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223 | |
224 | =item * Regular expression enhancements | |
225 | ||
fc952dec | 226 | You can now specify nongreedy quantifiers. You can now do grouping |
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227 | without creating a backreference. You can now write regular expressions |
228 | with embedded whitespace and comments for readability. A consistent | |
229 | extensibility mechanism has been added that is upwardly compatible with | |
230 | all old regular expressions. | |
231 | ||
5f05dabc | 232 | =item * Innumerable Unbundled Modules |
233 | ||
f102b883 TC |
234 | The Comprehensive Perl Archive Network described in L<perlmodlib> |
235 | contains hundreds of plug-and-play modules full of reusable code. | |
236 | See F<http://www.perl.com/CPAN> for a site near you. | |
5f05dabc | 237 | |
238 | =item * Compilability | |
239 | ||
240 | While not yet in full production mode, a working perl-to-C compiler | |
fc952dec | 241 | does exist. It can generate portable byte code, simple C, or |
5f05dabc | 242 | optimized C code. |
243 | ||
a0d0e21e LW |
244 | =back |
245 | ||
68dc0745 | 246 | Okay, that's I<definitely> enough hype. |
a0d0e21e LW |
247 | |
248 | =head1 ENVIRONMENT | |
249 | ||
1e422769 | 250 | See L<perlrun>. |
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251 | |
252 | =head1 AUTHOR | |
253 | ||
9607fc9c | 254 | Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks. |
a0d0e21e | 255 | |
a99b1639 TP |
256 | If your Perl success stories and testimonials may be of help to others |
257 | who wish to advocate the use of Perl in their applications, | |
258 | or if you wish to simply express your gratitude to Larry and the | |
259 | Perl developers, please write to <F<perl-thanks@perl.org>>. | |
260 | ||
a0d0e21e LW |
261 | =head1 FILES |
262 | ||
5f05dabc | 263 | "@INC" locations of perl libraries |
a0d0e21e LW |
264 | |
265 | =head1 SEE ALSO | |
266 | ||
267 | a2p awk to perl translator | |
4633a7c4 | 268 | |
a0d0e21e LW |
269 | s2p sed to perl translator |
270 | ||
271 | =head1 DIAGNOSTICS | |
272 | ||
273 | The B<-w> switch produces some lovely diagnostics. | |
274 | ||
5a964f20 TC |
275 | See L<perldiag> for explanations of all Perl's diagnostics. The C<use |
276 | diagnostics> pragma automatically turns Perl's normally terse warnings | |
277 | and errors into these longer forms. | |
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278 | |
279 | Compilation errors will tell you the line number of the error, with an | |
280 | indication of the next token or token type that was to be examined. | |
281 | (In the case of a script passed to Perl via B<-e> switches, each | |
282 | B<-e> is counted as one line.) | |
283 | ||
284 | Setuid scripts have additional constraints that can produce error | |
285 | messages such as "Insecure dependency". See L<perlsec>. | |
286 | ||
287 | Did we mention that you should definitely consider using the B<-w> | |
288 | switch? | |
289 | ||
290 | =head1 BUGS | |
291 | ||
292 | The B<-w> switch is not mandatory. | |
293 | ||
294 | Perl is at the mercy of your machine's definitions of various | |
1b3f7d21 CS |
295 | operations such as type casting, atof(), and floating-point |
296 | output with sprintf(). | |
a0d0e21e | 297 | |
748a9306 | 298 | If your stdio requires a seek or eof between reads and writes on a |
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299 | particular stream, so does Perl. (This doesn't apply to sysread() |
300 | and syswrite().) | |
301 | ||
302 | While none of the built-in data types have any arbitrary size limits | |
303 | (apart from memory size), there are still a few arbitrary limits: a | |
a30ac152 GS |
304 | given variable name may not be longer than 251 characters. Line numbers |
305 | displayed by diagnostics are internally stored as short integers, | |
306 | so they are limited to a maximum of 65535 (higher numbers usually being | |
307 | affected by wraparound). | |
a0d0e21e | 308 | |
b0607b7a LV |
309 | You may mail your bug reports (be sure to include full configuration |
310 | information as output by the myconfig program in the perl source tree, | |
9607fc9c | 311 | or by C<perl -V>) to <F<perlbug@perl.com>>. |
c07a80fd | 312 | If you've succeeded in compiling perl, the perlbug script in the utils/ |
313 | subdirectory can be used to help mail in a bug report. | |
4633a7c4 | 314 | |
a0d0e21e LW |
315 | Perl actually stands for Pathologically Eclectic Rubbish Lister, but |
316 | don't tell anyone I said that. | |
317 | ||
318 | =head1 NOTES | |
319 | ||
320 | The Perl motto is "There's more than one way to do it." Divining | |
321 | how many more is left as an exercise to the reader. | |
322 | ||
4633a7c4 | 323 | The three principal virtues of a programmer are Laziness, |
a0d0e21e | 324 | Impatience, and Hubris. See the Camel Book for why. |
16d20bd9 | 325 |