| 1 | =head1 NAME |
| 2 | |
| 3 | perl - Practical Extraction and Report Language |
| 4 | |
| 5 | =head1 SYNOPSIS |
| 6 | |
| 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> ]...> |
| 17 | |
| 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) |
| 22 | perldelta Perl changes since previous version |
| 23 | perl5005delta Perl changes in version 5.005 |
| 24 | perl5004delta Perl changes in version 5.004 |
| 25 | perlfaq Perl frequently asked questions |
| 26 | perltoc Perl documentation table of contents |
| 27 | |
| 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 |
| 34 | perlopentut Perl open() tutorial |
| 35 | perlvar Perl predefined variables |
| 36 | perlsub Perl subroutines |
| 37 | perlopentut Perl opening things tutorial |
| 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 |
| 43 | |
| 44 | perlref Perl references |
| 45 | perlreftut Perl references short introduction |
| 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 |
| 53 | perlthrtut Perl threads tutorial |
| 54 | |
| 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 |
| 61 | |
| 62 | perlpod Perl plain old documentation |
| 63 | perlbook Perl book information |
| 64 | |
| 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 |
| 71 | |
| 72 | perlhist Perl history records |
| 73 | |
| 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 | |
| 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: |
| 91 | |
| 92 | perl -V:man.dir |
| 93 | |
| 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. |
| 99 | |
| 100 | If that doesn't work for some reason, you can still use the |
| 101 | supplied F<perldoc> script to view module information. You might |
| 102 | also look into getting a replacement man program. |
| 103 | |
| 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 | |
| 110 | Perl is a language optimized for scanning arbitrary |
| 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, |
| 115 | elegant, minimal). |
| 116 | |
| 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 |
| 122 | expression syntax. Unlike most Unix utilities, Perl does not |
| 123 | arbitrarily limit the size of your data--if you've got the memory, |
| 124 | Perl can slurp in your whole file as a single string. Recursion is of |
| 125 | unlimited depth. And the tables used by hashes (sometimes called |
| 126 | "associative arrays") grow as necessary to prevent degraded |
| 127 | performance. Perl can use sophisticated pattern matching techniques to |
| 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. |
| 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 |
| 168 | to better privacy for "programming in the large". Anonymous |
| 169 | subroutines exhibit deep binding of lexical variables (closures). |
| 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 | |
| 191 | =item * Embeddable and Extensible |
| 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 |
| 197 | supported, and Perl itself can be made into a dynamic library. |
| 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 |
| 222 | semantics for undefined subroutine calls. It's not for just autoloading. |
| 223 | |
| 224 | =item * Regular expression enhancements |
| 225 | |
| 226 | You can now specify nongreedy quantifiers. You can now do grouping |
| 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 | |
| 232 | =item * Innumerable Unbundled Modules |
| 233 | |
| 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. |
| 237 | |
| 238 | =item * Compilability |
| 239 | |
| 240 | While not yet in full production mode, a working perl-to-C compiler |
| 241 | does exist. It can generate portable byte code, simple C, or |
| 242 | optimized C code. |
| 243 | |
| 244 | =back |
| 245 | |
| 246 | Okay, that's I<definitely> enough hype. |
| 247 | |
| 248 | =head1 ENVIRONMENT |
| 249 | |
| 250 | See L<perlrun>. |
| 251 | |
| 252 | =head1 AUTHOR |
| 253 | |
| 254 | Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks. |
| 255 | |
| 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 | |
| 261 | =head1 FILES |
| 262 | |
| 263 | "@INC" locations of perl libraries |
| 264 | |
| 265 | =head1 SEE ALSO |
| 266 | |
| 267 | a2p awk to perl translator |
| 268 | |
| 269 | s2p sed to perl translator |
| 270 | |
| 271 | =head1 DIAGNOSTICS |
| 272 | |
| 273 | The B<-w> switch produces some lovely diagnostics. |
| 274 | |
| 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. |
| 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 |
| 295 | operations such as type casting, atof(), and floating-point |
| 296 | output with sprintf(). |
| 297 | |
| 298 | If your stdio requires a seek or eof between reads and writes on a |
| 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 |
| 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). |
| 308 | |
| 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, |
| 311 | or by C<perl -V>) to <F<perlbug@perl.com>>. |
| 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. |
| 314 | |
| 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 | |
| 323 | The three principal virtues of a programmer are Laziness, |
| 324 | Impatience, and Hubris. See the Camel Book for why. |
| 325 | |