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  1. =head1 NAME
  2. perl - Practical Extraction and Report Language
  3. =head1 SYNOPSIS
  4. B<perl> S<[ B<-sTuU> ]>
  5. S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
  6. S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>
  7. S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>
  8. S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]>
  9. S<[ B<-P> ]>
  10. S<[ B<-S> ]>
  11. S<[ B<-x>[I<dir>] ]>
  12. S<[ B<-i>[I<extension>] ]>
  13. S<[ B<-e> I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
  14. For ease of access, the Perl manual has been split up into a number
  15. of sections:
  16. perl Perl overview (this section)
  17. perldelta Perl changes since previous version
  18. perl5004delta Perl changes in version 5.004
  19. perlfaq Perl frequently asked questions
  20. perltoc Perl documentation table of contents
  21. perldata Perl data structures
  22. perlsyn Perl syntax
  23. perlop Perl operators and precedence
  24. perlre Perl regular expressions
  25. perlrun Perl execution and options
  26. perlfunc Perl builtin functions
  27. perlopentut Perl open() tutorial
  28. perlvar Perl predefined variables
  29. perlsub Perl subroutines
  30. perlmod Perl modules: how they work
  31. perlmodlib Perl modules: how to write and use
  32. perlmodinstall Perl modules: how to install from CPAN
  33. perlform Perl formats
  34. perllocale Perl locale support
  35. perlref Perl references
  36. perlreftut Perl references short introduction
  37. perldsc Perl data structures intro
  38. perllol Perl data structures: lists of lists
  39. perltoot Perl OO tutorial
  40. perlobj Perl objects
  41. perltie Perl objects hidden behind simple variables
  42. perlbot Perl OO tricks and examples
  43. perlipc Perl interprocess communication
  44. perlthrtut Perl threads tutorial
  45. perldebug Perl debugging
  46. perldiag Perl diagnostic messages
  47. perlsec Perl security
  48. perltrap Perl traps for the unwary
  49. perlport Perl portability guide
  50. perlstyle Perl style guide
  51. perlpod Perl plain old documentation
  52. perlbook Perl book information
  53. perlembed Perl ways to embed perl in your C or C++ application
  54. perlapio Perl internal IO abstraction interface
  55. perlxs Perl XS application programming interface
  56. perlxstut Perl XS tutorial
  57. perlguts Perl internal functions for those doing extensions
  58. perlcall Perl calling conventions from C
  59. perlhist Perl history records
  60. (If you're intending to read these straight through for the first time,
  61. the suggested order will tend to reduce the number of forward references.)
  62. By default, all of the above manpages are installed in the
  63. F</usr/local/man/> directory.
  64. Extensive additional documentation for Perl modules is available. The
  65. default configuration for perl will place this additional documentation
  66. in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
  67. subdirectory of the Perl library directory). Some of this additional
  68. documentation is distributed standard with Perl, but you'll also find
  69. documentation for third-party modules there.
  70. You should be able to view Perl's documentation with your man(1)
  71. program by including the proper directories in the appropriate start-up
  72. files, or in the MANPATH environment variable. To find out where the
  73. configuration has installed the manpages, type:
  74. perl -V:man.dir
  75. If the directories have a common stem, such as F</usr/local/man/man1>
  76. and F</usr/local/man/man3>, you need only to add that stem
  77. (F</usr/local/man>) to your man(1) configuration files or your MANPATH
  78. environment variable. If they do not share a stem, you'll have to add
  79. both stems.
  80. If that doesn't work for some reason, you can still use the
  81. supplied F<perldoc> script to view module information. You might
  82. also look into getting a replacement man program.
  83. If something strange has gone wrong with your program and you're not
  84. sure where you should look for help, try the B<-w> switch first. It
  85. will often point out exactly where the trouble is.
  86. =head1 DESCRIPTION
  87. Perl is a language optimized for scanning arbitrary
  88. text files, extracting information from those text files, and printing
  89. reports based on that information. It's also a good language for many
  90. system management tasks. The language is intended to be practical
  91. (easy to use, efficient, complete) rather than beautiful (tiny,
  92. elegant, minimal).
  93. Perl combines (in the author's opinion, anyway) some of the best
  94. features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
  95. those languages should have little difficulty with it. (Language
  96. historians will also note some vestiges of B<csh>, Pascal, and even
  97. 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 of
  101. unlimited depth. And the tables used by hashes (sometimes called
  102. "associative arrays") grow as necessary to prevent degraded
  103. performance. Perl can use sophisticated pattern matching techniques to
  104. scan large amounts of data very quickly. Although optimized for
  105. scanning text, Perl can also deal with binary data, and can make dbm
  106. files look like hashes. Setuid Perl scripts are safer than C programs
  107. through a dataflow tracing mechanism which prevents many stupid
  108. security holes.
  109. If you have a problem that would ordinarily use B<sed> or B<awk> or
  110. B<sh>, but it exceeds their capabilities or must run a little faster,
  111. and you don't want to write the silly thing in C, then Perl may be for
  112. you. There are also translators to turn your B<sed> and B<awk>
  113. scripts into Perl scripts.
  114. But wait, there's more...
  115. Perl version 5 is nearly a complete rewrite, and provides
  116. the following additional benefits:
  117. =over 5
  118. =item * Many usability enhancements
  119. It is now possible to write much more readable Perl code (even within
  120. regular expressions). Formerly cryptic variable names can be replaced
  121. by mnemonic identifiers. Error messages are more informative, and the
  122. optional warnings will catch many of the mistakes a novice might make.
  123. This cannot be stressed enough. Whenever you get mysterious behavior,
  124. try the B<-w> switch!!! Whenever you don't get mysterious behavior,
  125. try using B<-w> anyway.
  126. =item * Simplified grammar
  127. The new yacc grammar is one half the size of the old one. Many of the
  128. arbitrary grammar rules have been regularized. The number of reserved
  129. words has been cut by 2/3. Despite this, nearly all old Perl scripts
  130. will continue to work unchanged.
  131. =item * Lexical scoping
  132. Perl variables may now be declared within a lexical scope, like "auto"
  133. variables in C. Not only is this more efficient, but it contributes
  134. to better privacy for "programming in the large". Anonymous
  135. subroutines exhibit deep binding of lexical variables (closures).
  136. =item * Arbitrarily nested data structures
  137. Any scalar value, including any array element, may now contain a
  138. reference to any other variable or subroutine. You can easily create
  139. anonymous variables and subroutines. Perl manages your reference
  140. counts for you.
  141. =item * Modularity and reusability
  142. The Perl library is now defined in terms of modules which can be easily
  143. shared among various packages. A package may choose to import all or a
  144. portion of a module's published interface. Pragmas (that is, compiler
  145. directives) are defined and used by the same mechanism.
  146. =item * Object-oriented programming
  147. A package can function as a class. Dynamic multiple inheritance and
  148. virtual methods are supported in a straightforward manner and with very
  149. little new syntax. Filehandles may now be treated as objects.
  150. =item * Embeddable and Extensible
  151. Perl may now be embedded easily in your C or C++ application, and can
  152. either call or be called by your routines through a documented
  153. interface. The XS preprocessor is provided to make it easy to glue
  154. your C or C++ routines into Perl. Dynamic loading of modules is
  155. supported, and Perl itself can be made into a dynamic library.
  156. =item * POSIX compliant
  157. A major new module is the POSIX module, which provides access to all
  158. available POSIX routines and definitions, via object classes where
  159. appropriate.
  160. =item * Package constructors and destructors
  161. The new BEGIN and END blocks provide means to capture control as
  162. a package is being compiled, and after the program exits. As a
  163. degenerate case they work just like awk's BEGIN and END when you
  164. use the B<-p> or B<-n> switches.
  165. =item * Multiple simultaneous DBM implementations
  166. A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
  167. files from the same script simultaneously. In fact, the old dbmopen
  168. interface has been generalized to allow any variable to be tied
  169. to an object class which defines its access methods.
  170. =item * Subroutine definitions may now be autoloaded
  171. In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
  172. semantics for undefined subroutine calls. It's not for just autoloading.
  173. =item * Regular expression enhancements
  174. You can now specify nongreedy quantifiers. You can now do grouping
  175. without creating a backreference. You can now write regular expressions
  176. with embedded whitespace and comments for readability. A consistent
  177. extensibility mechanism has been added that is upwardly compatible with
  178. all old regular expressions.
  179. =item * Innumerable Unbundled Modules
  180. The Comprehensive Perl Archive Network described in L<perlmodlib>
  181. contains hundreds of plug-and-play modules full of reusable code.
  182. See F<http://www.perl.com/CPAN> for a site near you.
  183. =item * Compilability
  184. While not yet in full production mode, a working perl-to-C compiler
  185. does exist. It can generate portable byte code, simple C, or
  186. optimized C code.
  187. =back
  188. Okay, that's I<definitely> enough hype.
  189. =head1 AVAILABILITY
  190. Perl is available for the vast majority of operating system platforms,
  191. including most Unix-like platforms. The following situation is as of
  192. February 1999 and Perl 5.005_03.
  193. The following platforms are able to build Perl from the standard
  194. source code distribution available at
  195. F<http://www.perl.com/CPAN/src/index.html>
  196. AIX Linux SCO ODT/OSR
  197. A/UX MachTen Solaris
  198. BeOS MPE/iX SunOS
  199. BSD/OS NetBSD SVR4
  200. DG/UX NextSTEP Tru64 UNIX 3)
  201. DomainOS OpenBSD Ultrix
  202. DOS DJGPP 1) OpenSTEP UNICOS
  203. DYNIX/ptx OS/2 VMS
  204. FreeBSD OS390 2) VOS
  205. HP-UX PowerMAX Windows 3.1 1)
  206. Hurd QNX Windows 95 1) 4)
  207. IRIX Windows 98 1) 4)
  208. Windows NT 1) 4)
  209. 1) in DOS mode either the DOS or OS/2 ports can be used
  210. 2) formerly known as MVS
  211. 3) formerly known as Digital UNIX and before that DEC OSF/1
  212. 4) compilers: Borland, Cygwin32, Mingw32 EGCS/GCC, VC++
  213. The following platforms have been known to build Perl from the source
  214. but for the Perl release 5.005_03 we haven't been able to verify them,
  215. either because the hardware/software platforms are rather rare or
  216. because we don't have an active champion on these platforms, or both.
  217. 3b1 FPS Plan 9
  218. AmigaOS GENIX PowerUX
  219. ConvexOS Greenhills RISC/os
  220. CX/UX ISC Stellar
  221. DC/OSx MachTen 68k SVR2
  222. DDE SMES MiNT TI1500
  223. DOS EMX MPC TitanOS
  224. Dynix NEWS-OS UNICOS/mk
  225. EP/IX Opus Unisys Dynix
  226. ESIX Unixware
  227. The following platforms are planned to be supported in the standard
  228. source code distribution of the Perl release 5.006 but are not
  229. supported in the Perl release 5.005_03:
  230. BS2000
  231. Netware
  232. Rhapsody
  233. VM/ESA
  234. The following platforms have their own source code distributions and
  235. binaries available via F<http://www.perl.com/CPAN/ports/index.html>.
  236. Perl release
  237. AS/400 5.003
  238. MacOS 5.004
  239. Netware 5.003_07
  240. Tandem Guardian 5.004
  241. The following platforms have only binaries available via
  242. F<http://www.perl.com/CPAN/ports/index.html>.
  243. Perl release
  244. Acorn RISCOS 5.005_02
  245. AOS 5.002
  246. LynxOS 5.004_02
  247. =head1 ENVIRONMENT
  248. See L<perlrun>.
  249. =head1 AUTHOR
  250. Larry Wall <F<[email protected]>>, with the help of oodles of other folks.
  251. If your Perl success stories and testimonials may be of help to others
  252. who wish to advocate the use of Perl in their applications,
  253. or if you wish to simply express your gratitude to Larry and the
  254. Perl developers, please write to <F<[email protected]>>.
  255. =head1 FILES
  256. "@INC" locations of perl libraries
  257. =head1 SEE ALSO
  258. a2p awk to perl translator
  259. s2p sed to perl translator
  260. =head1 DIAGNOSTICS
  261. The B<-w> switch produces some lovely diagnostics.
  262. See L<perldiag> for explanations of all Perl's diagnostics. The C<use
  263. diagnostics> pragma automatically turns Perl's normally terse warnings
  264. and errors into these longer forms.
  265. Compilation errors will tell you the line number of the error, with an
  266. indication of the next token or token type that was to be examined.
  267. (In the case of a script passed to Perl via B<-e> switches, each
  268. B<-e> is counted as one line.)
  269. Setuid scripts have additional constraints that can produce error
  270. messages such as "Insecure dependency". See L<perlsec>.
  271. Did we mention that you should definitely consider using the B<-w>
  272. switch?
  273. =head1 BUGS
  274. The B<-w> switch is not mandatory.
  275. Perl is at the mercy of your machine's definitions of various
  276. operations such as type casting, atof(), and floating-point
  277. output with sprintf().
  278. If your stdio requires a seek or eof between reads and writes on a
  279. particular stream, so does Perl. (This doesn't apply to sysread()
  280. and syswrite().)
  281. While none of the built-in data types have any arbitrary size limits
  282. (apart from memory size), there are still a few arbitrary limits: a
  283. given variable name may not be longer than 251 characters. Line numbers
  284. displayed by diagnostics are internally stored as short integers,
  285. so they are limited to a maximum of 65535 (higher numbers usually being
  286. affected by wraparound).
  287. You may mail your bug reports (be sure to include full configuration
  288. information as output by the myconfig program in the perl source tree,
  289. or by C<perl -V>) to <F<[email protected]>>.
  290. If you've succeeded in compiling perl, the perlbug script in the utils/
  291. subdirectory can be used to help mail in a bug report.
  292. Perl actually stands for Pathologically Eclectic Rubbish Lister, but
  293. don't tell anyone I said that.
  294. =head1 NOTES
  295. The Perl motto is "There's more than one way to do it." Divining
  296. how many more is left as an exercise to the reader.
  297. The three principal virtues of a programmer are Laziness,
  298. Impatience, and Hubris. See the Camel Book for why.