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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 | |
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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) | |
5f05dabc | 22 | perlnews Perl news about changes from previous version |
760ac839 | 23 | |
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24 | perldata Perl data structures |
25 | perlsyn Perl syntax | |
26 | perlop Perl operators and precedence | |
27 | perlre Perl regular expressions | |
28 | perlrun Perl execution and options | |
29 | perlfunc Perl builtin functions | |
30 | perlvar Perl predefined variables | |
31 | perlsub Perl subroutines | |
32 | perlmod Perl modules | |
760ac839 | 33 | perlform Perl formats |
5f05dabc | 34 | perllocale Perl locale support |
760ac839 | 35 | |
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36 | perlref Perl references |
37 | perldsc Perl data structures intro | |
38 | perllol Perl data structures: lists of lists | |
5f05dabc | 39 | perltoot Perl OO tutorial |
a0d0e21e | 40 | perlobj Perl objects |
cb1a09d0 | 41 | perltie Perl objects hidden behind simple variables |
a0d0e21e | 42 | perlbot Perl OO tricks and examples |
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43 | perlipc Perl interprocess communication |
44 | ||
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45 | perldebug Perl debugging |
46 | perldiag Perl diagnostic messages | |
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47 | perlsec Perl security |
48 | perltrap Perl traps for the unwary | |
49 | perlstyle Perl style guide | |
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50 | |
51 | perlpod Perl plain old documentation | |
52 | perlbook Perl book information | |
53 | ||
54 | perlembed Perl how to embed perl in your C or C++ app | |
55 | perlapio Perl internal IO abstraction interface | |
8e07c86e | 56 | perlxs Perl XS application programming interface |
4633a7c4 | 57 | perlxstut Perl XS tutorial |
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58 | perlguts Perl internal functions for those doing extensions |
59 | perlcall Perl calling conventions from C | |
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60 | |
61 | (If you're intending to read these straight through for the first time, | |
62 | the suggested order will tend to reduce the number of forward references.) | |
63 | ||
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64 | Additional documentation for Perl modules is available in the |
65 | F</usr/local/man/> directory. Some of this is distributed standard with | |
66 | Perl, but you'll also find third-party modules there. You should be able | |
67 | to view this with your man(1) program by including the proper directories | |
68 | in the appropriate start-up files. To find out where these are, type: | |
16d20bd9 | 69 | |
760ac839 | 70 | perl -V:man.dir |
16d20bd9 | 71 | |
4633a7c4 | 72 | If the directories were F</usr/local/man/man1> and F</usr/local/man/man3>, |
5f05dabc | 73 | you would need to add only F</usr/local/man> to your MANPATH. If |
4633a7c4 | 74 | they are different, you'll have to add both stems. |
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75 | |
76 | If that doesn't work for some reason, you can still use the | |
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77 | supplied F<perldoc> script to view module information. You might |
78 | also look into getting a replacement man program. | |
16d20bd9 | 79 | |
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80 | If something strange has gone wrong with your program and you're not |
81 | sure where you should look for help, try the B<-w> switch first. It | |
82 | will often point out exactly where the trouble is. | |
83 | ||
84 | =head1 DESCRIPTION | |
85 | ||
5f05dabc | 86 | Perl is a language optimized for scanning arbitrary |
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87 | text files, extracting information from those text files, and printing |
88 | reports based on that information. It's also a good language for many | |
89 | system management tasks. The language is intended to be practical | |
90 | (easy to use, efficient, complete) rather than beautiful (tiny, | |
94d58c47 | 91 | elegant, minimal). |
92 | ||
93 | Perl combines (in the author's opinion, anyway) some | |
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94 | of the best features of C, B<sed>, B<awk>, and B<sh>, so people |
95 | familiar with those languages should have little difficulty with it. | |
96 | (Language historians will also note some vestiges of B<csh>, Pascal, | |
97 | and even BASIC-PLUS.) Expression syntax corresponds quite closely to C | |
98 | expression syntax. Unlike most Unix utilities, Perl does not | |
99 | arbitrarily limit the size of your data--if you've got the memory, | |
100 | Perl can slurp in your whole file as a single string. Recursion is | |
101 | of unlimited depth. And the hash tables used by associative arrays | |
102 | grow as necessary to prevent degraded performance. Perl uses | |
103 | sophisticated pattern matching techniques to scan large amounts of data | |
104 | very quickly. Although optimized for scanning text, Perl can also | |
105 | deal with binary data, and can make dbm files look like associative | |
c07a80fd | 106 | arrays. Setuid Perl scripts are safer than |
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107 | C programs through a dataflow tracing mechanism which prevents many |
108 | stupid security holes. If you have a problem that would ordinarily use | |
109 | B<sed> or B<awk> or B<sh>, but it exceeds their capabilities or must | |
110 | run a little faster, and you don't want to write the silly thing in C, | |
111 | then Perl may be for you. There are also translators to turn your | |
112 | B<sed> and B<awk> scripts into Perl scripts. | |
113 | ||
114 | But wait, there's more... | |
115 | ||
116 | Perl version 5 is nearly a complete rewrite, and provides | |
117 | the following additional benefits: | |
118 | ||
119 | =over 5 | |
120 | ||
121 | =item * Many usability enhancements | |
122 | ||
123 | It is now possible to write much more readable Perl code (even within | |
124 | regular expressions). Formerly cryptic variable names can be replaced | |
125 | by mnemonic identifiers. Error messages are more informative, and the | |
126 | optional warnings will catch many of the mistakes a novice might make. | |
127 | This cannot be stressed enough. Whenever you get mysterious behavior, | |
128 | try the B<-w> switch!!! Whenever you don't get mysterious behavior, | |
129 | try using B<-w> anyway. | |
130 | ||
131 | =item * Simplified grammar | |
132 | ||
133 | The new yacc grammar is one half the size of the old one. Many of the | |
134 | arbitrary grammar rules have been regularized. The number of reserved | |
135 | words has been cut by 2/3. Despite this, nearly all old Perl scripts | |
136 | will continue to work unchanged. | |
137 | ||
138 | =item * Lexical scoping | |
139 | ||
140 | Perl variables may now be declared within a lexical scope, like "auto" | |
141 | variables in C. Not only is this more efficient, but it contributes | |
5f05dabc | 142 | to better privacy for "programming in the large". Anonymous |
143 | subroutines exhibit deep binding of lexical variables (closures). | |
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144 | |
145 | =item * Arbitrarily nested data structures | |
146 | ||
147 | Any scalar value, including any array element, may now contain a | |
148 | reference to any other variable or subroutine. You can easily create | |
149 | anonymous variables and subroutines. Perl manages your reference | |
150 | counts for you. | |
151 | ||
152 | =item * Modularity and reusability | |
153 | ||
154 | The Perl library is now defined in terms of modules which can be easily | |
155 | shared among various packages. A package may choose to import all or a | |
156 | portion of a module's published interface. Pragmas (that is, compiler | |
157 | directives) are defined and used by the same mechanism. | |
158 | ||
159 | =item * Object-oriented programming | |
160 | ||
161 | A package can function as a class. Dynamic multiple inheritance and | |
162 | virtual methods are supported in a straightforward manner and with very | |
163 | little new syntax. Filehandles may now be treated as objects. | |
164 | ||
c07a80fd | 165 | =item * Embeddable and Extensible |
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166 | |
167 | Perl may now be embedded easily in your C or C++ application, and can | |
168 | either call or be called by your routines through a documented | |
169 | interface. The XS preprocessor is provided to make it easy to glue | |
170 | your C or C++ routines into Perl. Dynamic loading of modules is | |
5f05dabc | 171 | supported, and Perl itself can be made into a dynamic library. |
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172 | |
173 | =item * POSIX compliant | |
174 | ||
175 | A major new module is the POSIX module, which provides access to all | |
176 | available POSIX routines and definitions, via object classes where | |
177 | appropriate. | |
178 | ||
179 | =item * Package constructors and destructors | |
180 | ||
181 | The new BEGIN and END blocks provide means to capture control as | |
182 | a package is being compiled, and after the program exits. As a | |
183 | degenerate case they work just like awk's BEGIN and END when you | |
184 | use the B<-p> or B<-n> switches. | |
185 | ||
186 | =item * Multiple simultaneous DBM implementations | |
187 | ||
188 | A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB | |
189 | files from the same script simultaneously. In fact, the old dbmopen | |
190 | interface has been generalized to allow any variable to be tied | |
191 | to an object class which defines its access methods. | |
192 | ||
193 | =item * Subroutine definitions may now be autoloaded | |
194 | ||
195 | In fact, the AUTOLOAD mechanism also allows you to define any arbitrary | |
5f05dabc | 196 | semantics for undefined subroutine calls. It's not for just autoloading. |
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197 | |
198 | =item * Regular expression enhancements | |
199 | ||
200 | You can now specify non-greedy quantifiers. You can now do grouping | |
201 | without creating a backreference. You can now write regular expressions | |
202 | with embedded whitespace and comments for readability. A consistent | |
203 | extensibility mechanism has been added that is upwardly compatible with | |
204 | all old regular expressions. | |
205 | ||
5f05dabc | 206 | =item * Innumerable Unbundled Modules |
207 | ||
208 | The Comprehensive Perl Archive Network described in L<perlmod> | |
209 | contains hundreds of plug-and-play modules full of reusable | |
210 | code. See F<http://www.perl.com/CPAN> for a site near you. | |
211 | ||
212 | =item * Compilability | |
213 | ||
214 | While not yet in full production mode, a working perl-to-C compiler | |
215 | does exist. It can generate portable bytecode, simple C, or | |
216 | optimized C code. | |
217 | ||
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218 | =back |
219 | ||
220 | Ok, that's I<definitely> enough hype. | |
221 | ||
222 | =head1 ENVIRONMENT | |
223 | ||
224 | =over 12 | |
225 | ||
226 | =item HOME | |
227 | ||
228 | Used if chdir has no argument. | |
229 | ||
230 | =item LOGDIR | |
231 | ||
232 | Used if chdir has no argument and HOME is not set. | |
233 | ||
234 | =item PATH | |
235 | ||
236 | Used in executing subprocesses, and in finding the script if B<-S> is | |
237 | used. | |
238 | ||
239 | =item PERL5LIB | |
240 | ||
241 | A colon-separated list of directories in which to look for Perl library | |
242 | files before looking in the standard library and the current | |
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243 | directory. If PERL5LIB is not defined, PERLLIB is used. When running |
244 | taint checks (because the script was running setuid or setgid, or the | |
245 | B<-T> switch was used), neither variable is used. The script should | |
246 | instead say | |
247 | ||
248 | use lib "/my/directory"; | |
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249 | |
250 | =item PERL5DB | |
251 | ||
252 | The command used to get the debugger code. If unset, uses | |
253 | ||
254 | BEGIN { require 'perl5db.pl' } | |
255 | ||
5f05dabc | 256 | =item PERL_DESTRUCT_LEVEL |
257 | ||
258 | Relevant only if your perl executable was built with B<-DDEBUGGING>, | |
259 | this controls the behavior of global destruction of objects and other | |
260 | references. | |
261 | ||
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262 | =item PERLLIB |
263 | ||
264 | A colon-separated list of directories in which to look for Perl library | |
265 | files before looking in the standard library and the current | |
266 | directory. If PERL5LIB is defined, PERLLIB is not used. | |
267 | ||
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268 | =back |
269 | ||
a034a98d DD |
270 | Perl also has environment variables that control how Perl handles data |
271 | specific to particular natural languages. See L<perllocale>. | |
fb252e81 | 272 | |
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273 | Apart from these, Perl uses no other environment variables, except |
274 | to make them available to the script being executed, and to child | |
275 | processes. However, scripts running setuid would do well to execute | |
276 | the following lines before doing anything else, just to keep people | |
277 | honest: | |
278 | ||
279 | $ENV{'PATH'} = '/bin:/usr/bin'; # or whatever you need | |
280 | $ENV{'SHELL'} = '/bin/sh' if defined $ENV{'SHELL'}; | |
281 | $ENV{'IFS'} = '' if defined $ENV{'IFS'}; | |
282 | ||
283 | =head1 AUTHOR | |
284 | ||
fb252e81 | 285 | Larry Wall E<lt>F<larry@wall.org>E<gt>, with the help of oodles of other folks. |
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286 | |
287 | =head1 FILES | |
288 | ||
289 | "/tmp/perl-e$$" temporary file for -e commands | |
5f05dabc | 290 | "@INC" locations of perl libraries |
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291 | |
292 | =head1 SEE ALSO | |
293 | ||
294 | a2p awk to perl translator | |
4633a7c4 | 295 | |
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296 | s2p sed to perl translator |
297 | ||
298 | =head1 DIAGNOSTICS | |
299 | ||
300 | The B<-w> switch produces some lovely diagnostics. | |
301 | ||
302 | See L<perldiag> for explanations of all Perl's diagnostics. | |
303 | ||
304 | Compilation errors will tell you the line number of the error, with an | |
305 | indication of the next token or token type that was to be examined. | |
306 | (In the case of a script passed to Perl via B<-e> switches, each | |
307 | B<-e> is counted as one line.) | |
308 | ||
309 | Setuid scripts have additional constraints that can produce error | |
310 | messages such as "Insecure dependency". See L<perlsec>. | |
311 | ||
312 | Did we mention that you should definitely consider using the B<-w> | |
313 | switch? | |
314 | ||
315 | =head1 BUGS | |
316 | ||
317 | The B<-w> switch is not mandatory. | |
318 | ||
319 | Perl is at the mercy of your machine's definitions of various | |
5f05dabc | 320 | operations such as type casting, atof(), and sprintf(). The latter |
321 | can even trigger a core dump when passed ludicrous input values. | |
a0d0e21e | 322 | |
748a9306 | 323 | If your stdio requires a seek or eof between reads and writes on a |
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324 | particular stream, so does Perl. (This doesn't apply to sysread() |
325 | and syswrite().) | |
326 | ||
327 | While none of the built-in data types have any arbitrary size limits | |
328 | (apart from memory size), there are still a few arbitrary limits: a | |
d357d931 | 329 | given variable name may not be longer than 255 characters, and no |
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330 | component of your PATH may be longer than 255 if you use B<-S>. A regular |
331 | expression may not compile to more than 32767 bytes internally. | |
332 | ||
5f05dabc | 333 | See the perl bugs database at F<http://www.perl.com/perl/bugs/>. You may |
cb1a09d0 | 334 | mail your bug reports (be sure to include full configuration information |
fb252e81 | 335 | as output by the myconfig program in the perl source tree, or by C<perl -V>) to |
cb1a09d0 | 336 | F<perlbug@perl.com>. |
c07a80fd | 337 | If you've succeeded in compiling perl, the perlbug script in the utils/ |
338 | subdirectory can be used to help mail in a bug report. | |
4633a7c4 | 339 | |
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340 | Perl actually stands for Pathologically Eclectic Rubbish Lister, but |
341 | don't tell anyone I said that. | |
342 | ||
343 | =head1 NOTES | |
344 | ||
345 | The Perl motto is "There's more than one way to do it." Divining | |
346 | how many more is left as an exercise to the reader. | |
347 | ||
4633a7c4 | 348 | The three principal virtues of a programmer are Laziness, |
a0d0e21e | 349 | Impatience, and Hubris. See the Camel Book for why. |
16d20bd9 | 350 |