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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 | ||
21 | perl Perl overview (this section) | |
774d564b | 22 | perldelta Perl changes since previous version |
68dc0745 | 23 | perlfaq Perl frequently asked questions |
a3cb178b | 24 | perltoc Perl documentation table of contents |
760ac839 | 25 | |
a0d0e21e LW |
26 | perldata Perl data structures |
27 | perlsyn Perl syntax | |
28 | perlop Perl operators and precedence | |
29 | perlre Perl regular expressions | |
30 | perlrun Perl execution and options | |
31 | perlfunc Perl builtin functions | |
32 | perlvar Perl predefined variables | |
33 | perlsub Perl subroutines | |
f102b883 TC |
34 | perlmod Perl modules: how they work |
35 | perlmodlib Perl modules: how to write and use | |
760ac839 | 36 | perlform Perl formats |
5f05dabc | 37 | perllocale Perl locale support |
760ac839 | 38 | |
fc952dec | 39 | perlref Perl references |
4633a7c4 LW |
40 | perldsc Perl data structures intro |
41 | perllol Perl data structures: lists of lists | |
5f05dabc | 42 | perltoot Perl OO tutorial |
a0d0e21e | 43 | perlobj Perl objects |
cb1a09d0 | 44 | perltie Perl objects hidden behind simple variables |
a0d0e21e | 45 | perlbot Perl OO tricks and examples |
760ac839 LW |
46 | perlipc Perl interprocess communication |
47 | ||
a0d0e21e LW |
48 | perldebug Perl debugging |
49 | perldiag Perl diagnostic messages | |
a0d0e21e LW |
50 | perlsec Perl security |
51 | perltrap Perl traps for the unwary | |
52 | perlstyle Perl style guide | |
760ac839 LW |
53 | |
54 | perlpod Perl plain old documentation | |
55 | perlbook Perl book information | |
56 | ||
fc952dec | 57 | perlembed Perl ways to embed perl in your C or C++ application |
760ac839 | 58 | perlapio Perl internal IO abstraction interface |
8e07c86e | 59 | perlxs Perl XS application programming interface |
4633a7c4 | 60 | perlxstut Perl XS tutorial |
fc952dec | 61 | perlguts Perl internal functions for those doing extensions |
a0d0e21e | 62 | perlcall Perl calling conventions from C |
a0d0e21e | 63 | |
d516a115 JH |
64 | perlhist Perl history records |
65 | ||
a0d0e21e LW |
66 | (If you're intending to read these straight through for the first time, |
67 | the suggested order will tend to reduce the number of forward references.) | |
68 | ||
fc952dec CS |
69 | By default, all of the above manpages are installed in the |
70 | F</usr/local/man/> directory. | |
71 | ||
72 | Extensive additional documentation for Perl modules is available. The | |
73 | default configuration for perl will place this additional documentation | |
74 | in the F</usr/local/lib/perl5/man> directory (or else in the F<man> | |
75 | subdirectory of the Perl library directory). Some of this additional | |
76 | documentation is distributed standard with Perl, but you'll also find | |
77 | documentation for third-party modules there. | |
78 | ||
79 | You should be able to view Perl's documentation with your man(1) | |
80 | program by including the proper directories in the appropriate start-up | |
81 | files, or in the MANPATH environment variable. To find out where the | |
82 | configuration has installed the manpages, type: | |
16d20bd9 | 83 | |
760ac839 | 84 | perl -V:man.dir |
16d20bd9 | 85 | |
fc952dec CS |
86 | If the directories have a common stem, such as F</usr/local/man/man1> |
87 | and F</usr/local/man/man3>, you need only to add that stem | |
88 | (F</usr/local/man>) to your man(1) configuration files or your MANPATH | |
89 | environment variable. If they do not share a stem, you'll have to add | |
90 | both stems. | |
16d20bd9 AD |
91 | |
92 | If that doesn't work for some reason, you can still use the | |
4633a7c4 LW |
93 | supplied F<perldoc> script to view module information. You might |
94 | also look into getting a replacement man program. | |
16d20bd9 | 95 | |
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96 | If something strange has gone wrong with your program and you're not |
97 | sure where you should look for help, try the B<-w> switch first. It | |
98 | will often point out exactly where the trouble is. | |
99 | ||
100 | =head1 DESCRIPTION | |
101 | ||
5f05dabc | 102 | Perl is a language optimized for scanning arbitrary |
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103 | text files, extracting information from those text files, and printing |
104 | reports based on that information. It's also a good language for many | |
105 | system management tasks. The language is intended to be practical | |
106 | (easy to use, efficient, complete) rather than beautiful (tiny, | |
94d58c47 | 107 | elegant, minimal). |
108 | ||
aa689395 | 109 | Perl combines (in the author's opinion, anyway) some of the best |
110 | features of C, B<sed>, B<awk>, and B<sh>, so people familiar with | |
111 | those languages should have little difficulty with it. (Language | |
112 | historians will also note some vestiges of B<csh>, Pascal, and even | |
113 | BASIC-PLUS.) Expression syntax corresponds quite closely to C | |
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114 | expression syntax. Unlike most Unix utilities, Perl does not |
115 | arbitrarily limit the size of your data--if you've got the memory, | |
aa689395 | 116 | Perl can slurp in your whole file as a single string. Recursion is of |
117 | unlimited depth. And the tables used by hashes (previously called | |
118 | "associative arrays") grow as necessary to prevent degraded | |
119 | performance. Perl uses sophisticated pattern matching techniques to | |
120 | scan large amounts of data very quickly. Although optimized for | |
121 | scanning text, Perl can also deal with binary data, and can make dbm | |
122 | files look like hashes. Setuid Perl scripts are safer than C programs | |
123 | through a dataflow tracing mechanism which prevents many stupid | |
124 | security holes. | |
125 | ||
126 | If you have a problem that would ordinarily use B<sed> or B<awk> or | |
127 | B<sh>, but it exceeds their capabilities or must run a little faster, | |
128 | and you don't want to write the silly thing in C, then Perl may be for | |
129 | you. There are also translators to turn your B<sed> and B<awk> | |
130 | scripts into Perl scripts. | |
a0d0e21e LW |
131 | |
132 | But wait, there's more... | |
133 | ||
134 | Perl version 5 is nearly a complete rewrite, and provides | |
135 | the following additional benefits: | |
136 | ||
137 | =over 5 | |
138 | ||
139 | =item * Many usability enhancements | |
140 | ||
141 | It is now possible to write much more readable Perl code (even within | |
142 | regular expressions). Formerly cryptic variable names can be replaced | |
143 | by mnemonic identifiers. Error messages are more informative, and the | |
144 | optional warnings will catch many of the mistakes a novice might make. | |
145 | This cannot be stressed enough. Whenever you get mysterious behavior, | |
146 | try the B<-w> switch!!! Whenever you don't get mysterious behavior, | |
147 | try using B<-w> anyway. | |
148 | ||
149 | =item * Simplified grammar | |
150 | ||
151 | The new yacc grammar is one half the size of the old one. Many of the | |
152 | arbitrary grammar rules have been regularized. The number of reserved | |
153 | words has been cut by 2/3. Despite this, nearly all old Perl scripts | |
154 | will continue to work unchanged. | |
155 | ||
156 | =item * Lexical scoping | |
157 | ||
158 | Perl variables may now be declared within a lexical scope, like "auto" | |
159 | variables in C. Not only is this more efficient, but it contributes | |
fc952dec | 160 | to better privacy for "programming in the large". Anonymous |
5f05dabc | 161 | subroutines exhibit deep binding of lexical variables (closures). |
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162 | |
163 | =item * Arbitrarily nested data structures | |
164 | ||
165 | Any scalar value, including any array element, may now contain a | |
166 | reference to any other variable or subroutine. You can easily create | |
167 | anonymous variables and subroutines. Perl manages your reference | |
168 | counts for you. | |
169 | ||
170 | =item * Modularity and reusability | |
171 | ||
172 | The Perl library is now defined in terms of modules which can be easily | |
173 | shared among various packages. A package may choose to import all or a | |
174 | portion of a module's published interface. Pragmas (that is, compiler | |
175 | directives) are defined and used by the same mechanism. | |
176 | ||
177 | =item * Object-oriented programming | |
178 | ||
179 | A package can function as a class. Dynamic multiple inheritance and | |
180 | virtual methods are supported in a straightforward manner and with very | |
181 | little new syntax. Filehandles may now be treated as objects. | |
182 | ||
c07a80fd | 183 | =item * Embeddable and Extensible |
a0d0e21e LW |
184 | |
185 | Perl may now be embedded easily in your C or C++ application, and can | |
186 | either call or be called by your routines through a documented | |
187 | interface. The XS preprocessor is provided to make it easy to glue | |
188 | your C or C++ routines into Perl. Dynamic loading of modules is | |
5f05dabc | 189 | supported, and Perl itself can be made into a dynamic library. |
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190 | |
191 | =item * POSIX compliant | |
192 | ||
193 | A major new module is the POSIX module, which provides access to all | |
194 | available POSIX routines and definitions, via object classes where | |
195 | appropriate. | |
196 | ||
197 | =item * Package constructors and destructors | |
198 | ||
199 | The new BEGIN and END blocks provide means to capture control as | |
200 | a package is being compiled, and after the program exits. As a | |
201 | degenerate case they work just like awk's BEGIN and END when you | |
202 | use the B<-p> or B<-n> switches. | |
203 | ||
204 | =item * Multiple simultaneous DBM implementations | |
205 | ||
206 | A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB | |
207 | files from the same script simultaneously. In fact, the old dbmopen | |
208 | interface has been generalized to allow any variable to be tied | |
209 | to an object class which defines its access methods. | |
210 | ||
211 | =item * Subroutine definitions may now be autoloaded | |
212 | ||
213 | In fact, the AUTOLOAD mechanism also allows you to define any arbitrary | |
5f05dabc | 214 | semantics for undefined subroutine calls. It's not for just autoloading. |
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215 | |
216 | =item * Regular expression enhancements | |
217 | ||
fc952dec | 218 | You can now specify nongreedy quantifiers. You can now do grouping |
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219 | without creating a backreference. You can now write regular expressions |
220 | with embedded whitespace and comments for readability. A consistent | |
221 | extensibility mechanism has been added that is upwardly compatible with | |
222 | all old regular expressions. | |
223 | ||
5f05dabc | 224 | =item * Innumerable Unbundled Modules |
225 | ||
f102b883 TC |
226 | The Comprehensive Perl Archive Network described in L<perlmodlib> |
227 | contains hundreds of plug-and-play modules full of reusable code. | |
228 | See F<http://www.perl.com/CPAN> for a site near you. | |
5f05dabc | 229 | |
230 | =item * Compilability | |
231 | ||
232 | While not yet in full production mode, a working perl-to-C compiler | |
fc952dec | 233 | does exist. It can generate portable byte code, simple C, or |
5f05dabc | 234 | optimized C code. |
235 | ||
a0d0e21e LW |
236 | =back |
237 | ||
68dc0745 | 238 | Okay, that's I<definitely> enough hype. |
a0d0e21e LW |
239 | |
240 | =head1 ENVIRONMENT | |
241 | ||
1e422769 | 242 | See L<perlrun>. |
a0d0e21e LW |
243 | |
244 | =head1 AUTHOR | |
245 | ||
9607fc9c | 246 | Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks. |
a0d0e21e | 247 | |
a99b1639 TP |
248 | If your Perl success stories and testimonials may be of help to others |
249 | who wish to advocate the use of Perl in their applications, | |
250 | or if you wish to simply express your gratitude to Larry and the | |
251 | Perl developers, please write to <F<perl-thanks@perl.org>>. | |
252 | ||
a0d0e21e LW |
253 | =head1 FILES |
254 | ||
255 | "/tmp/perl-e$$" temporary file for -e commands | |
5f05dabc | 256 | "@INC" locations of perl libraries |
a0d0e21e LW |
257 | |
258 | =head1 SEE ALSO | |
259 | ||
260 | a2p awk to perl translator | |
4633a7c4 | 261 | |
a0d0e21e LW |
262 | s2p sed to perl translator |
263 | ||
264 | =head1 DIAGNOSTICS | |
265 | ||
266 | The B<-w> switch produces some lovely diagnostics. | |
267 | ||
268 | See L<perldiag> for explanations of all Perl's diagnostics. | |
269 | ||
270 | Compilation errors will tell you the line number of the error, with an | |
271 | indication of the next token or token type that was to be examined. | |
272 | (In the case of a script passed to Perl via B<-e> switches, each | |
273 | B<-e> is counted as one line.) | |
274 | ||
275 | Setuid scripts have additional constraints that can produce error | |
276 | messages such as "Insecure dependency". See L<perlsec>. | |
277 | ||
278 | Did we mention that you should definitely consider using the B<-w> | |
279 | switch? | |
280 | ||
281 | =head1 BUGS | |
282 | ||
283 | The B<-w> switch is not mandatory. | |
284 | ||
285 | Perl is at the mercy of your machine's definitions of various | |
1b3f7d21 CS |
286 | operations such as type casting, atof(), and floating-point |
287 | output with sprintf(). | |
a0d0e21e | 288 | |
748a9306 | 289 | If your stdio requires a seek or eof between reads and writes on a |
a0d0e21e LW |
290 | particular stream, so does Perl. (This doesn't apply to sysread() |
291 | and syswrite().) | |
292 | ||
293 | While none of the built-in data types have any arbitrary size limits | |
294 | (apart from memory size), there are still a few arbitrary limits: a | |
d357d931 | 295 | given variable name may not be longer than 255 characters, and no |
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296 | component of your PATH may be longer than 255 if you use B<-S>. A regular |
297 | expression may not compile to more than 32767 bytes internally. | |
298 | ||
b0607b7a LV |
299 | You may mail your bug reports (be sure to include full configuration |
300 | information as output by the myconfig program in the perl source tree, | |
9607fc9c | 301 | or by C<perl -V>) to <F<perlbug@perl.com>>. |
c07a80fd | 302 | If you've succeeded in compiling perl, the perlbug script in the utils/ |
303 | subdirectory can be used to help mail in a bug report. | |
4633a7c4 | 304 | |
a0d0e21e LW |
305 | Perl actually stands for Pathologically Eclectic Rubbish Lister, but |
306 | don't tell anyone I said that. | |
307 | ||
308 | =head1 NOTES | |
309 | ||
310 | The Perl motto is "There's more than one way to do it." Divining | |
311 | how many more is left as an exercise to the reader. | |
312 | ||
4633a7c4 | 313 | The three principal virtues of a programmer are Laziness, |
a0d0e21e | 314 | Impatience, and Hubris. See the Camel Book for why. |
16d20bd9 | 315 |