| 1 | =head1 NAME |
| 2 | |
| 3 | perlport - Writing portable Perl |
| 4 | |
| 5 | =head1 DESCRIPTION |
| 6 | |
| 7 | Perl runs on numerous operating systems. While most of them share |
| 8 | much in common, they also have their own unique features. |
| 9 | |
| 10 | This document is meant to help you to find out what constitutes portable |
| 11 | Perl code. That way once you make a decision to write portably, |
| 12 | you know where the lines are drawn, and you can stay within them. |
| 13 | |
| 14 | There is a tradeoff between taking full advantage of one particular |
| 15 | type of computer and taking advantage of a full range of them. |
| 16 | Naturally, as you broaden your range and become more diverse, the |
| 17 | common factors drop, and you are left with an increasingly smaller |
| 18 | area of common ground in which you can operate to accomplish a |
| 19 | particular task. Thus, when you begin attacking a problem, it is |
| 20 | important to consider under which part of the tradeoff curve you |
| 21 | want to operate. Specifically, you must decide whether it is |
| 22 | important that the task that you are coding have the full generality |
| 23 | of being portable, or whether to just get the job done right now. |
| 24 | This is the hardest choice to be made. The rest is easy, because |
| 25 | Perl provides many choices, whichever way you want to approach your |
| 26 | problem. |
| 27 | |
| 28 | Looking at it another way, writing portable code is usually about |
| 29 | willfully limiting your available choices. Naturally, it takes |
| 30 | discipline and sacrifice to do that. The product of portability |
| 31 | and convenience may be a constant. You have been warned. |
| 32 | |
| 33 | Be aware of two important points: |
| 34 | |
| 35 | =over 4 |
| 36 | |
| 37 | =item Not all Perl programs have to be portable |
| 38 | |
| 39 | There is no reason you should not use Perl as a language to glue Unix |
| 40 | tools together, or to prototype a Macintosh application, or to manage the |
| 41 | Windows registry. If it makes no sense to aim for portability for one |
| 42 | reason or another in a given program, then don't bother. |
| 43 | |
| 44 | =item Nearly all of Perl already I<is> portable |
| 45 | |
| 46 | Don't be fooled into thinking that it is hard to create portable Perl |
| 47 | code. It isn't. Perl tries its level-best to bridge the gaps between |
| 48 | what's available on different platforms, and all the means available to |
| 49 | use those features. Thus almost all Perl code runs on any machine |
| 50 | without modification. But there are some significant issues in |
| 51 | writing portable code, and this document is entirely about those issues. |
| 52 | |
| 53 | =back |
| 54 | |
| 55 | Here's the general rule: When you approach a task commonly done |
| 56 | using a whole range of platforms, think about writing portable |
| 57 | code. That way, you don't sacrifice much by way of the implementation |
| 58 | choices you can avail yourself of, and at the same time you can give |
| 59 | your users lots of platform choices. On the other hand, when you have to |
| 60 | take advantage of some unique feature of a particular platform, as is |
| 61 | often the case with systems programming (whether for Unix, Windows, |
| 62 | S<Mac OS>, VMS, etc.), consider writing platform-specific code. |
| 63 | |
| 64 | When the code will run on only two or three operating systems, you |
| 65 | may need to consider only the differences of those particular systems. |
| 66 | The important thing is to decide where the code will run and to be |
| 67 | deliberate in your decision. |
| 68 | |
| 69 | The material below is separated into three main sections: main issues of |
| 70 | portability (L<"ISSUES">, platform-specific issues (L<"PLATFORMS">, and |
| 71 | built-in perl functions that behave differently on various ports |
| 72 | (L<"FUNCTION IMPLEMENTATIONS">. |
| 73 | |
| 74 | This information should not be considered complete; it includes possibly |
| 75 | transient information about idiosyncrasies of some of the ports, almost |
| 76 | all of which are in a state of constant evolution. Thus, this material |
| 77 | should be considered a perpetual work in progress |
| 78 | (E<lt>IMG SRC="yellow_sign.gif" ALT="Under Construction"E<gt>). |
| 79 | |
| 80 | =head1 ISSUES |
| 81 | |
| 82 | =head2 Newlines |
| 83 | |
| 84 | In most operating systems, lines in files are terminated by newlines. |
| 85 | Just what is used as a newline may vary from OS to OS. Unix |
| 86 | traditionally uses C<\012>, one type of DOSish I/O uses C<\015\012>, |
| 87 | and S<Mac OS> uses C<\015>. |
| 88 | |
| 89 | Perl uses C<\n> to represent the "logical" newline, where what is |
| 90 | logical may depend on the platform in use. In MacPerl, C<\n> always |
| 91 | means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but |
| 92 | when accessing a file in "text" mode, STDIO translates it to (or |
| 93 | from) C<\015\012>, depending on whether your reading or writing. |
| 94 | Unix does the same thing on ttys in canonical mode. C<\015\012> |
| 95 | is commonly referred to as CRLF. |
| 96 | |
| 97 | Because of the "text" mode translation, DOSish perls have limitations |
| 98 | in using C<seek> and C<tell> on a file accessed in "text" mode. |
| 99 | Stick to C<seek>-ing to locations you got from C<tell> (and no |
| 100 | others), and you are usually free to use C<seek> and C<tell> even |
| 101 | in "text" mode. Using C<seek> or C<tell> or other file operations |
| 102 | may be non-portable. If you use C<binmode> on a file, however, you |
| 103 | can usually C<seek> and C<tell> with arbitrary values in safety. |
| 104 | |
| 105 | A common misconception in socket programming is that C<\n> eq C<\012> |
| 106 | everywhere. When using protocols such as common Internet protocols, |
| 107 | C<\012> and C<\015> are called for specifically, and the values of |
| 108 | the logical C<\n> and C<\r> (carriage return) are not reliable. |
| 109 | |
| 110 | print SOCKET "Hi there, client!\r\n"; # WRONG |
| 111 | print SOCKET "Hi there, client!\015\012"; # RIGHT |
| 112 | |
| 113 | However, using C<\015\012> (or C<\cM\cJ>, or C<\x0D\x0A>) can be tedious |
| 114 | and unsightly, as well as confusing to those maintaining the code. As |
| 115 | such, the Socket module supplies the Right Thing for those who want it. |
| 116 | |
| 117 | use Socket qw(:DEFAULT :crlf); |
| 118 | print SOCKET "Hi there, client!$CRLF" # RIGHT |
| 119 | |
| 120 | When reading from a socket, remember that the default input record |
| 121 | separator C<$/> is C<\n>, but robust socket code will recognize as |
| 122 | either C<\012> or C<\015\012> as end of line: |
| 123 | |
| 124 | while (<SOCKET>) { |
| 125 | # ... |
| 126 | } |
| 127 | |
| 128 | Because both CRLF and LF end in LF, the input record separator can |
| 129 | be set to LF and any CR stripped later. Better to write: |
| 130 | |
| 131 | use Socket qw(:DEFAULT :crlf); |
| 132 | local($/) = LF; # not needed if $/ is already \012 |
| 133 | |
| 134 | while (<SOCKET>) { |
| 135 | s/$CR?$LF/\n/; # not sure if socket uses LF or CRLF, OK |
| 136 | # s/\015?\012/\n/; # same thing |
| 137 | } |
| 138 | |
| 139 | This example is preferred over the previous one--even for Unix |
| 140 | platforms--because now any C<\015>'s (C<\cM>'s) are stripped out |
| 141 | (and there was much rejoicing). |
| 142 | |
| 143 | Similarly, functions that return text data--such as a function that |
| 144 | fetches a web page--should sometimes translate newlines before |
| 145 | returning the data, if they've not yet been translated to the local |
| 146 | newline representation. A single line of code will often suffice: |
| 147 | |
| 148 | $data =~ s/\015?\012/\n/g; |
| 149 | return $data; |
| 150 | |
| 151 | Some of this may be confusing. Here's a handy reference to the ASCII CR |
| 152 | and LF characters. You can print it out and stick it in your wallet. |
| 153 | |
| 154 | LF == \012 == \x0A == \cJ == ASCII 10 |
| 155 | CR == \015 == \x0D == \cM == ASCII 13 |
| 156 | |
| 157 | | Unix | DOS | Mac | |
| 158 | --------------------------- |
| 159 | \n | LF | LF | CR | |
| 160 | \r | CR | CR | LF | |
| 161 | \n * | LF | CRLF | CR | |
| 162 | \r * | CR | CR | LF | |
| 163 | --------------------------- |
| 164 | * text-mode STDIO |
| 165 | |
| 166 | The Unix column assumes that you are not accessing a serial line |
| 167 | (like a tty) in canonical mode. If you are, then CR on input becomes |
| 168 | "\n", and "\n" on output becomes CRLF. |
| 169 | |
| 170 | These are just the most common definitions of C<\n> and C<\r> in Perl. |
| 171 | There may well be others. |
| 172 | |
| 173 | =head2 Numbers endianness and Width |
| 174 | |
| 175 | Different CPUs store integers and floating point numbers in different |
| 176 | orders (called I<endianness>) and widths (32-bit and 64-bit being the |
| 177 | most common today). This affects your programs when they attempt to transfer |
| 178 | numbers in binary format from one CPU architecture to another, |
| 179 | usually either "live" via network connection, or by storing the |
| 180 | numbers to secondary storage such as a disk file or tape. |
| 181 | |
| 182 | Conflicting storage orders make utter mess out of the numbers. If a |
| 183 | little-endian host (Intel, Alpha) stores 0x12345678 (305419896 in |
| 184 | decimal), a big-endian host (Motorola, MIPS, Sparc, PA) reads it as |
| 185 | 0x78563412 (2018915346 in decimal). To avoid this problem in network |
| 186 | (socket) connections use the C<pack> and C<unpack> formats C<n> |
| 187 | and C<N>, the "network" orders. These are guaranteed to be portable. |
| 188 | |
| 189 | Differing widths can cause truncation even between platforms of equal |
| 190 | endianness. The platform of shorter width loses the upper parts of the |
| 191 | number. There is no good solution for this problem except to avoid |
| 192 | transferring or storing raw binary numbers. |
| 193 | |
| 194 | One can circumnavigate both these problems in two ways. Either |
| 195 | transfer and store numbers always in text format, instead of raw |
| 196 | binary, or else consider using modules like Data::Dumper (included in |
| 197 | the standard distribution as of Perl 5.005) and Storable. Keeping |
| 198 | all data as text significantly simplifies matters. |
| 199 | |
| 200 | =head2 Files and Filesystems |
| 201 | |
| 202 | Most platforms these days structure files in a hierarchical fashion. |
| 203 | So, it is reasonably safe to assume that all platforms support the |
| 204 | notion of a "path" to uniquely identify a file on the system. How |
| 205 | that path is really written, though, differs considerably. |
| 206 | |
| 207 | Atlhough similar, file path specifications differ between Unix, |
| 208 | Windows, S<Mac OS>, OS/2, VMS, VOS, S<RISC OS>, and probably others. |
| 209 | Unix, for example, is one of the few OSes that has the elegant idea |
| 210 | of a single root directory. |
| 211 | |
| 212 | DOS, OS/2, VMS, VOS, and Windows can work similarly to Unix with C</> |
| 213 | as path separator, or in their own idiosyncratic ways (such as having |
| 214 | several root directories and various "unrooted" device files such NIL: |
| 215 | and LPT:). |
| 216 | |
| 217 | S<Mac OS> uses C<:> as a path separator instead of C</>. |
| 218 | |
| 219 | The filesystem may support neither hard links (C<link>) nor |
| 220 | symbolic links (C<symlink>, C<readlink>, C<lstat>). |
| 221 | |
| 222 | The filesystem may support neither access timestamp nor change |
| 223 | timestamp (meaning that about the only portable timestamp is the |
| 224 | modification timestamp), or one second granularity of any timestamps |
| 225 | (e.g. the FAT filesystem limits the time granularity to two seconds). |
| 226 | |
| 227 | VOS perl can emulate Unix filenames with C</> as path separator. The |
| 228 | native pathname characters greater-than, less-than, number-sign, and |
| 229 | percent-sign are always accepted. |
| 230 | |
| 231 | S<RISC OS> perl can emulate Unix filenames with C</> as path |
| 232 | separator, or go native and use C<.> for path separator and C<:> to |
| 233 | signal filesystems and disk names. |
| 234 | |
| 235 | If all this is intimidating, have no (well, maybe only a little) |
| 236 | fear. There are modules that can help. The File::Spec modules |
| 237 | provide methods to do the Right Thing on whatever platform happens |
| 238 | to be running the program. |
| 239 | |
| 240 | use File::Spec::Functions; |
| 241 | chdir(updir()); # go up one directory |
| 242 | $file = catfile(curdir(), 'temp', 'file.txt'); |
| 243 | # on Unix and Win32, './temp/file.txt' |
| 244 | # on Mac OS, ':temp:file.txt' |
| 245 | |
| 246 | File::Spec is available in the standard distribution as of version |
| 247 | 5.004_05. |
| 248 | |
| 249 | In general, production code should not have file paths hardcoded. |
| 250 | Making them user-supplied or read from a configuration file is |
| 251 | better, keeping in mind that file path syntax varies on different |
| 252 | machines. |
| 253 | |
| 254 | This is especially noticeable in scripts like Makefiles and test suites, |
| 255 | which often assume C</> as a path separator for subdirectories. |
| 256 | |
| 257 | Also of use is File::Basename from the standard distribution, which |
| 258 | splits a pathname into pieces (base filename, full path to directory, |
| 259 | and file suffix). |
| 260 | |
| 261 | Even when on a single platform (if you can call Unix a single platform), |
| 262 | remember not to count on the existence or the contents of particular |
| 263 | system-specific files or directories, like F</etc/passwd>, |
| 264 | F</etc/sendmail.conf>, F</etc/resolv.conf>, or even F</tmp/>. For |
| 265 | example, F</etc/passwd> may exist but not contain the encrypted |
| 266 | passwords, because the system is using some form of enhanced security. |
| 267 | Or it may not contain all the accounts, because the system is using NIS. |
| 268 | If code does need to rely on such a file, include a description of the |
| 269 | file and its format in the code's documentation, then make it easy for |
| 270 | the user to override the default location of the file. |
| 271 | |
| 272 | Don't assume a text file will end with a newline. They should, |
| 273 | but people forget. |
| 274 | |
| 275 | Do not have two files of the same name with different case, like |
| 276 | F<test.pl> and F<Test.pl>, as many platforms have case-insensitive |
| 277 | filenames. Also, try not to have non-word characters (except for C<.>) |
| 278 | in the names, and keep them to the 8.3 convention, for maximum |
| 279 | portability, onerous a burden though this may appear. |
| 280 | |
| 281 | Likewise, when using the AutoSplit module, try to keep your functions to |
| 282 | 8.3 naming and case-insensitive conventions; or, at the least, |
| 283 | make it so the resulting files have a unique (case-insensitively) |
| 284 | first 8 characters. |
| 285 | |
| 286 | Whitespace in filenames is tolerated on most systems, but not all. |
| 287 | Many systems (DOS, VMS) cannot have more than one C<.> in their filenames. |
| 288 | |
| 289 | Don't assume C<E<gt>> won't be the first character of a filename. |
| 290 | Always use C<E<lt>> explicitly to open a file for reading, |
| 291 | unless you want the user to be able to specify a pipe open. |
| 292 | |
| 293 | open(FILE, "< $existing_file") or die $!; |
| 294 | |
| 295 | If filenames might use strange characters, it is safest to open it |
| 296 | with C<sysopen> instead of C<open>. C<open> is magic and can |
| 297 | translate characters like C<E<gt>>, C<E<lt>>, and C<|>, which may |
| 298 | be the wrong thing to do. (Sometimes, though, it's the right thing.) |
| 299 | |
| 300 | =head2 System Interaction |
| 301 | |
| 302 | Not all platforms provide a command line. These are usually platforms |
| 303 | that rely primarily on a Graphical User Interface (GUI) for user |
| 304 | interaction. A program requiring a command line interface might |
| 305 | not work everywhere. This is probably for the user of the program |
| 306 | to deal with, so don't stay up late worrying about it. |
| 307 | |
| 308 | Some platforms can't delete or rename files held open by the system. |
| 309 | Remember to C<close> files when you are done with them. Don't |
| 310 | C<unlink> or C<rename> an open file. Don't C<tie> or C<open> a |
| 311 | file already tied or opened; C<untie> or C<close> it first. |
| 312 | |
| 313 | Don't open the same file more than once at a time for writing, as some |
| 314 | operating systems put mandatory locks on such files. |
| 315 | |
| 316 | Don't count on a specific environment variable existing in C<%ENV>. |
| 317 | Don't count on C<%ENV> entries being case-sensitive, or even |
| 318 | case-preserving. |
| 319 | |
| 320 | Don't count on signals for anything. |
| 321 | |
| 322 | Don't count on filename globbing. Use C<opendir>, C<readdir>, and |
| 323 | C<closedir> instead. |
| 324 | |
| 325 | Don't count on per-program environment variables, or per-program current |
| 326 | directories. |
| 327 | |
| 328 | Don't count on specific values of C<$!>. |
| 329 | |
| 330 | =head2 Interprocess Communication (IPC) |
| 331 | |
| 332 | In general, don't directly access the system in code meant to be |
| 333 | portable. That means, no C<system>, C<exec>, C<fork>, C<pipe>, |
| 334 | C<``>, C<qx//>, C<open> with a C<|>, nor any of the other things |
| 335 | that makes being a perl hacker worth being. |
| 336 | |
| 337 | Commands that launch external processes are generally supported on |
| 338 | most platforms (though many of them do not support any type of |
| 339 | forking). The problem with using them arises from what you invoke |
| 340 | them on. External tools are often named differently on different |
| 341 | platforms, may not be available in the same location, migth accept |
| 342 | different arguments, can behave differently, and often present their |
| 343 | results in a platform-dependent way. Thus, you should seldom depend |
| 344 | on them to produce consistent results. (Then again, if you're calling |
| 345 | I<netstat -a>, you probably don't expect it to run on both Unix and CP/M.) |
| 346 | |
| 347 | One especially common bit of Perl code is opening a pipe to B<sendmail>: |
| 348 | |
| 349 | open(MAIL, '|/usr/lib/sendmail -t') |
| 350 | or die "cannot fork sendmail: $!"; |
| 351 | |
| 352 | This is fine for systems programming when sendmail is known to be |
| 353 | available. But it is not fine for many non-Unix systems, and even |
| 354 | some Unix systems that may not have sendmail installed. If a portable |
| 355 | solution is needed, see the various distributions on CPAN that deal |
| 356 | with it. Mail::Mailer and Mail::Send in the MailTools distribution are |
| 357 | commonly used, and provide several mailing methods, including mail, |
| 358 | sendmail, and direct SMTP (via Net::SMTP) if a mail transfer agent is |
| 359 | not available. Mail::Sendmail is a standalone module that provides |
| 360 | simple, platform-independent mailing. |
| 361 | |
| 362 | The Unix System V IPC (C<msg*(), sem*(), shm*()>) is not available |
| 363 | even on all Unix platforms. |
| 364 | |
| 365 | The rule of thumb for portable code is: Do it all in portable Perl, or |
| 366 | use a module (that may internally implement it with platform-specific |
| 367 | code, but expose a common interface). |
| 368 | |
| 369 | =head2 External Subroutines (XS) |
| 370 | |
| 371 | XS code can usually be made to work with any platform, but dependent |
| 372 | libraries, header files, etc., might not be readily available or |
| 373 | portable, or the XS code itself might be platform-specific, just as Perl |
| 374 | code might be. If the libraries and headers are portable, then it is |
| 375 | normally reasonable to make sure the XS code is portable, too. |
| 376 | |
| 377 | A different type of portability issue arises when writing XS code: |
| 378 | availability of a C compiler on the end-user's system. C brings |
| 379 | with it its own portability issues, and writing XS code will expose |
| 380 | you to some of those. Writing purely in Perl is an easier way to |
| 381 | achieve portability. |
| 382 | |
| 383 | =head2 Standard Modules |
| 384 | |
| 385 | In general, the standard modules work across platforms. Notable |
| 386 | exceptions are the CPAN module (which currently makes connections to external |
| 387 | programs that may not be available), platform-specific modules (like |
| 388 | ExtUtils::MM_VMS), and DBM modules. |
| 389 | |
| 390 | There is no one DBM module available on all platforms. |
| 391 | SDBM_File and the others are generally available on all Unix and DOSish |
| 392 | ports, but not in MacPerl, where only NBDM_File and DB_File are |
| 393 | available. |
| 394 | |
| 395 | The good news is that at least some DBM module should be available, and |
| 396 | AnyDBM_File will use whichever module it can find. Of course, then |
| 397 | the code needs to be fairly strict, dropping to the greatest common |
| 398 | factor (e.g., not exceeding 1K for each record), so that it will |
| 399 | work with any DBM module. See L<AnyDBM_File> for more details. |
| 400 | |
| 401 | =head2 Time and Date |
| 402 | |
| 403 | The system's notion of time of day and calendar date is controlled in |
| 404 | widely different ways. Don't assume the timezone is stored in C<$ENV{TZ}>, |
| 405 | and even if it is, don't assume that you can control the timezone through |
| 406 | that variable. |
| 407 | |
| 408 | Don't assume that the epoch starts at 00:00:00, January 1, 1970, |
| 409 | because that is OS- and implementation-specific. It is better to store a date |
| 410 | in an unambiguous representation. The ISO-8601 standard defines |
| 411 | "YYYY-MM-DD" as the date format. A text representation (like "1987-12-18") |
| 412 | can be easily converted into an OS-specific value using a module like |
| 413 | Date::Parse. An array of values, such as those returned by |
| 414 | C<localtime>, can be converted to an OS-specific representation using |
| 415 | Time::Local. |
| 416 | |
| 417 | When calculating specific times, such as for tests in time or date modules, |
| 418 | it may be appropriate to calculate an offset for the epoch. |
| 419 | |
| 420 | require Time::Local; |
| 421 | $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70); |
| 422 | |
| 423 | The value for C<$offset> in Unix will be C<0>, but in Mac OS will be |
| 424 | some large number. C<$offset> can then be added to a Unix time value |
| 425 | to get what should be the proper value on any system. |
| 426 | |
| 427 | =head2 Character sets and character encoding |
| 428 | |
| 429 | Assume little about character sets. Assume nothing about |
| 430 | numerical values (C<ord>, C<chr>) of characters. Do not |
| 431 | assume that the alphabetic characters are encoded contiguously (in |
| 432 | the numeric sense). Do not assume anything about the ordering of the |
| 433 | characters. The lowercase letters may come before or after the |
| 434 | uppercase letters; the lowercase and uppercase may be interlaced so |
| 435 | that both `a' and `A' come before `b'; the accented and other |
| 436 | international characters may be interlaced so that E<auml> comes |
| 437 | before `b'. |
| 438 | |
| 439 | =head2 Internationalisation |
| 440 | |
| 441 | If you may assume POSIX (a rather large assumption), you may read |
| 442 | more about the POSIX locale system from L<perllocale>. The locale |
| 443 | system at least attempts to make things a little bit more portable, |
| 444 | or at least more convenient and native-friendly for non-English |
| 445 | users. The system affects character sets and encoding, and date |
| 446 | and time formatting--amongst other things. |
| 447 | |
| 448 | =head2 System Resources |
| 449 | |
| 450 | If your code is destined for systems with severely constrained (or |
| 451 | missing!) virtual memory systems then you want to be I<especially> mindful |
| 452 | of avoiding wasteful constructs such as: |
| 453 | |
| 454 | # NOTE: this is no longer "bad" in perl5.005 |
| 455 | for (0..10000000) {} # bad |
| 456 | for (my $x = 0; $x <= 10000000; ++$x) {} # good |
| 457 | |
| 458 | @lines = <VERY_LARGE_FILE>; # bad |
| 459 | |
| 460 | while (<FILE>) {$file .= $_} # sometimes bad |
| 461 | $file = join('', <FILE>); # better |
| 462 | |
| 463 | The last two constructs may appear unintuitive to most people. The |
| 464 | first repeatedly grows a string, whereas the second allocates a |
| 465 | large chunk of memory in one go. On some systems, the second is |
| 466 | more efficient that the first. |
| 467 | |
| 468 | =head2 Security |
| 469 | |
| 470 | Most multi-user platforms provide basic levels of security, usually |
| 471 | implemented at the filesystem level. Some, however, do |
| 472 | not--unfortunately. Thus the notion of user id, or "home" directory, |
| 473 | or even the state of being logged-in, may be unrecognizable on many |
| 474 | platforms. If you write programs that are security-conscious, it |
| 475 | is usually best to know what type of system you will be running |
| 476 | under so that you can write code explicitly for that platform (or |
| 477 | class of platforms). |
| 478 | |
| 479 | =head2 Style |
| 480 | |
| 481 | For those times when it is necessary to have platform-specific code, |
| 482 | consider keeping the platform-specific code in one place, making porting |
| 483 | to other platforms easier. Use the Config module and the special |
| 484 | variable C<$^O> to differentiate platforms, as described in |
| 485 | L<"PLATFORMS">. |
| 486 | |
| 487 | Be careful in the tests you supply with your module or programs. |
| 488 | Module code may be fully portable, but its tests might not be. This |
| 489 | often happens when tests spawn off other processes or call external |
| 490 | programs to aid in the testing, or when (as noted above) the tests |
| 491 | assume certain things about the filesystem and paths. Be careful |
| 492 | not to depend on a specific output style for errors, such as when |
| 493 | checking C<$!> after an system call. Some platforms expect a certain |
| 494 | output format, and perl on those platforms may have been adjusted |
| 495 | accordingly. Most specifically, don't anchor a regex when testing |
| 496 | an error value. |
| 497 | |
| 498 | =head1 CPAN Testers |
| 499 | |
| 500 | Modules uploaded to CPAN are tested by a variety of volunteers on |
| 501 | different platforms. These CPAN testers are notified by mail of each |
| 502 | new upload, and reply to the list with PASS, FAIL, NA (not applicable to |
| 503 | this platform), or UNKNOWN (unknown), along with any relevant notations. |
| 504 | |
| 505 | The purpose of the testing is twofold: one, to help developers fix any |
| 506 | problems in their code that crop up because of lack of testing on other |
| 507 | platforms; two, to provide users with information about whether |
| 508 | a given module works on a given platform. |
| 509 | |
| 510 | =over 4 |
| 511 | |
| 512 | =item Mailing list: cpan-testers@perl.org |
| 513 | |
| 514 | =item Testing results: C<http://www.perl.org/cpan-testers/> |
| 515 | |
| 516 | =back |
| 517 | |
| 518 | =head1 PLATFORMS |
| 519 | |
| 520 | As of version 5.002, Perl is built with a C<$^O> variable that |
| 521 | indicates the operating system it was built on. This was implemented |
| 522 | to help speed up code that would otherwise have to C<use Config> |
| 523 | and use the value of C<$Config{osname}>. Of course, to get more |
| 524 | detailed information about the system, looking into C<%Config> is |
| 525 | certainly recommended. |
| 526 | |
| 527 | C<%Config> cannot always be trusted, however, because it was built |
| 528 | at compile time. If perl was built in one place, then transferred |
| 529 | elsewhere, some values may be wrong. The values may even have been |
| 530 | edited after the fact. |
| 531 | |
| 532 | =head2 Unix |
| 533 | |
| 534 | Perl works on a bewildering variety of Unix and Unix-like platforms (see |
| 535 | e.g. most of the files in the F<hints/> directory in the source code kit). |
| 536 | On most of these systems, the value of C<$^O> (hence C<$Config{'osname'}>, |
| 537 | too) is determined by lowercasing and stripping punctuation from the first |
| 538 | field of the string returned by typing C<uname -a> (or a similar command) |
| 539 | at the shell prompt. Here, for example, are a few of the more popular |
| 540 | Unix flavors: |
| 541 | |
| 542 | uname $^O $Config{'archname'} |
| 543 | -------------------------------------------- |
| 544 | AIX aix aix |
| 545 | BSD/OS bsdos i386-bsdos |
| 546 | dgux dgux AViiON-dgux |
| 547 | DYNIX/ptx dynixptx i386-dynixptx |
| 548 | FreeBSD freebsd freebsd-i386 |
| 549 | Linux linux i386-linux |
| 550 | Linux linux i586-linux |
| 551 | Linux linux ppc-linux |
| 552 | HP-UX hpux PA-RISC1.1 |
| 553 | IRIX irix irix |
| 554 | openbsd openbsd i386-openbsd |
| 555 | OSF1 dec_osf alpha-dec_osf |
| 556 | reliantunix-n svr4 RM400-svr4 |
| 557 | SCO_SV sco_sv i386-sco_sv |
| 558 | SINIX-N svr4 RM400-svr4 |
| 559 | sn4609 unicos CRAY_C90-unicos |
| 560 | sn6521 unicosmk t3e-unicosmk |
| 561 | sn9617 unicos CRAY_J90-unicos |
| 562 | SunOS solaris sun4-solaris |
| 563 | SunOS solaris i86pc-solaris |
| 564 | SunOS4 sunos sun4-sunos |
| 565 | |
| 566 | Because the value of C<$Config{archname}> may depend on the |
| 567 | hardware architecture, it can vary more than the value of C<$^O>. |
| 568 | |
| 569 | =head2 DOS and Derivatives |
| 570 | |
| 571 | Perl has long been ported to Intel-style microcomputers running under |
| 572 | systems like PC-DOS, MS-DOS, OS/2, and most Windows platforms you can |
| 573 | bring yourself to mention (except for Windows CE, if you count that). |
| 574 | Users familiar with I<COMMAND.COM> or I<CMD.EXE> style shells should |
| 575 | be aware that each of these file specifications may have subtle |
| 576 | differences: |
| 577 | |
| 578 | $filespec0 = "c:/foo/bar/file.txt"; |
| 579 | $filespec1 = "c:\\foo\\bar\\file.txt"; |
| 580 | $filespec2 = 'c:\foo\bar\file.txt'; |
| 581 | $filespec3 = 'c:\\foo\\bar\\file.txt'; |
| 582 | |
| 583 | System calls accept either C</> or C<\> as the path separator. |
| 584 | However, many command-line utilities of DOS vintage treat C</> as |
| 585 | the option prefix, so may get confused by filenames containing C</>. |
| 586 | Aside from calling any external programs, C</> will work just fine, |
| 587 | and probably better, as it is more consistent with popular usage, |
| 588 | and avoids the problem of remembering what to backwhack and what |
| 589 | not to. |
| 590 | |
| 591 | The DOS FAT filesystem can accommodate only "8.3" style filenames. Under |
| 592 | the "case-insensitive, but case-preserving" HPFS (OS/2) and NTFS (NT) |
| 593 | filesystems you may have to be careful about case returned with functions |
| 594 | like C<readdir> or used with functions like C<open> or C<opendir>. |
| 595 | |
| 596 | DOS also treats several filenames as special, such as AUX, PRN, |
| 597 | NUL, CON, COM1, LPT1, LPT2, etc. Unfortunately, sometimes these |
| 598 | filenames won't even work if you include an explicit directory |
| 599 | prefix. It is best to avoid such filenames, if you want your code |
| 600 | to be portable to DOS and its derivatives. It's hard to know what |
| 601 | these all are, unfortunately. |
| 602 | |
| 603 | Users of these operating systems may also wish to make use of |
| 604 | scripts such as I<pl2bat.bat> or I<pl2cmd> to |
| 605 | put wrappers around your scripts. |
| 606 | |
| 607 | Newline (C<\n>) is translated as C<\015\012> by STDIO when reading from |
| 608 | and writing to files (see L<"Newlines">). C<binmode(FILEHANDLE)> |
| 609 | will keep C<\n> translated as C<\012> for that filehandle. Since it is a |
| 610 | no-op on other systems, C<binmode> should be used for cross-platform code |
| 611 | that deals with binary data. That's assuming you realize in advance |
| 612 | that your data is in binary. General-purpose programs should |
| 613 | often assume nothing about their data. |
| 614 | |
| 615 | The C<$^O> variable and the C<$Config{archname}> values for various |
| 616 | DOSish perls are as follows: |
| 617 | |
| 618 | OS $^O $Config{'archname'} |
| 619 | -------------------------------------------- |
| 620 | MS-DOS dos |
| 621 | PC-DOS dos |
| 622 | OS/2 os2 |
| 623 | Windows 95 MSWin32 MSWin32-x86 |
| 624 | Windows 98 MSWin32 MSWin32-x86 |
| 625 | Windows NT MSWin32 MSWin32-x86 |
| 626 | Windows NT MSWin32 MSWin32-ALPHA |
| 627 | Windows NT MSWin32 MSWin32-ppc |
| 628 | |
| 629 | Also see: |
| 630 | |
| 631 | =over 4 |
| 632 | |
| 633 | =item The djgpp environment for DOS, C<http://www.delorie.com/djgpp/> |
| 634 | |
| 635 | =item The EMX environment for DOS, OS/2, etc. C<emx@iaehv.nl>, |
| 636 | C<http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html> or |
| 637 | C<ftp://hobbes.nmsu.edu/pub/os2/dev/emx> |
| 638 | |
| 639 | =item Build instructions for Win32, L<perlwin32>. |
| 640 | |
| 641 | =item The ActiveState Pages, C<http://www.activestate.com/> |
| 642 | |
| 643 | =back |
| 644 | |
| 645 | =head2 S<Mac OS> |
| 646 | |
| 647 | Any module requiring XS compilation is right out for most people, because |
| 648 | MacPerl is built using non-free (and non-cheap!) compilers. Some XS |
| 649 | modules that can work with MacPerl are built and distributed in binary |
| 650 | form on CPAN. |
| 651 | |
| 652 | Directories are specified as: |
| 653 | |
| 654 | volume:folder:file for absolute pathnames |
| 655 | volume:folder: for absolute pathnames |
| 656 | :folder:file for relative pathnames |
| 657 | :folder: for relative pathnames |
| 658 | :file for relative pathnames |
| 659 | file for relative pathnames |
| 660 | |
| 661 | Files are stored in the directory in alphabetical order. Filenames are |
| 662 | limited to 31 characters, and may include any character except for |
| 663 | null and C<:>, which is reserved as the path separator. |
| 664 | |
| 665 | Instead of C<flock>, see C<FSpSetFLock> and C<FSpRstFLock> in the |
| 666 | Mac::Files module, or C<chmod(0444, ...)> and C<chmod(0666, ...)>. |
| 667 | |
| 668 | In the MacPerl application, you can't run a program from the command line; |
| 669 | programs that expect C<@ARGV> to be populated can be edited with something |
| 670 | like the following, which brings up a dialog box asking for the command |
| 671 | line arguments. |
| 672 | |
| 673 | if (!@ARGV) { |
| 674 | @ARGV = split /\s+/, MacPerl::Ask('Arguments?'); |
| 675 | } |
| 676 | |
| 677 | A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full |
| 678 | pathnames of the files dropped onto the script. |
| 679 | |
| 680 | Mac users can run programs under a type of command line interface |
| 681 | under MPW (Macintosh Programmer's Workshop, a free development |
| 682 | environment from Apple). MacPerl was first introduced as an MPW |
| 683 | tool, and MPW can be used like a shell: |
| 684 | |
| 685 | perl myscript.plx some arguments |
| 686 | |
| 687 | ToolServer is another app from Apple that provides access to MPW tools |
| 688 | from MPW and the MacPerl app, which allows MacPerl programs to use |
| 689 | C<system>, backticks, and piped C<open>. |
| 690 | |
| 691 | "S<Mac OS>" is the proper name for the operating system, but the value |
| 692 | in C<$^O> is "MacOS". To determine architecture, version, or whether |
| 693 | the application or MPW tool version is running, check: |
| 694 | |
| 695 | $is_app = $MacPerl::Version =~ /App/; |
| 696 | $is_tool = $MacPerl::Version =~ /MPW/; |
| 697 | ($version) = $MacPerl::Version =~ /^(\S+)/; |
| 698 | $is_ppc = $MacPerl::Architecture eq 'MacPPC'; |
| 699 | $is_68k = $MacPerl::Architecture eq 'Mac68K'; |
| 700 | |
| 701 | S<Mac OS X> and S<Mac OS X Server>, based on NeXT's OpenStep OS, will |
| 702 | (in theory) be able to run MacPerl natively, under the "Classic" |
| 703 | environment. The new "Cocoa" environment (formerly called the "Yellow Box") |
| 704 | may run a slightly modified version of MacPerl, using the Carbon interfaces. |
| 705 | |
| 706 | S<Mac OS X Server> and its Open Source version, Darwin, both run Unix |
| 707 | perl natively (with a few patches). Full support for these |
| 708 | is slated for perl 5.6. |
| 709 | |
| 710 | Also see: |
| 711 | |
| 712 | =over 4 |
| 713 | |
| 714 | =item The MacPerl Pages, C<http://www.macperl.com/>. |
| 715 | |
| 716 | =item The MacPerl mailing lists, C<http://www.macperl.org/>. |
| 717 | |
| 718 | =item MacPerl Module Porters, C<http://pudge.net/mmp/>. |
| 719 | |
| 720 | =back |
| 721 | |
| 722 | =head2 VMS |
| 723 | |
| 724 | Perl on VMS is discussed in F<vms/perlvms.pod> in the perl distribution. |
| 725 | Perl on VMS can accept either VMS- or Unix-style file |
| 726 | specifications as in either of the following: |
| 727 | |
| 728 | $ perl -ne "print if /perl_setup/i" SYS$LOGIN:LOGIN.COM |
| 729 | $ perl -ne "print if /perl_setup/i" /sys$login/login.com |
| 730 | |
| 731 | but not a mixture of both as in: |
| 732 | |
| 733 | $ perl -ne "print if /perl_setup/i" sys$login:/login.com |
| 734 | Can't open sys$login:/login.com: file specification syntax error |
| 735 | |
| 736 | Interacting with Perl from the Digital Command Language (DCL) shell |
| 737 | often requires a different set of quotation marks than Unix shells do. |
| 738 | For example: |
| 739 | |
| 740 | $ perl -e "print ""Hello, world.\n""" |
| 741 | Hello, world. |
| 742 | |
| 743 | There are several ways to wrap your perl scripts in DCL F<.COM> files, if |
| 744 | you are so inclined. For example: |
| 745 | |
| 746 | $ write sys$output "Hello from DCL!" |
| 747 | $ if p1 .eqs. "" |
| 748 | $ then perl -x 'f$environment("PROCEDURE") |
| 749 | $ else perl -x - 'p1 'p2 'p3 'p4 'p5 'p6 'p7 'p8 |
| 750 | $ deck/dollars="__END__" |
| 751 | #!/usr/bin/perl |
| 752 | |
| 753 | print "Hello from Perl!\n"; |
| 754 | |
| 755 | __END__ |
| 756 | $ endif |
| 757 | |
| 758 | Do take care with C<$ ASSIGN/nolog/user SYS$COMMAND: SYS$INPUT> if your |
| 759 | perl-in-DCL script expects to do things like C<$read = E<lt>STDINE<gt>;>. |
| 760 | |
| 761 | Filenames are in the format "name.extension;version". The maximum |
| 762 | length for filenames is 39 characters, and the maximum length for |
| 763 | extensions is also 39 characters. Version is a number from 1 to |
| 764 | 32767. Valid characters are C</[A-Z0-9$_-]/>. |
| 765 | |
| 766 | VMS's RMS filesystem is case-insensitive and does not preserve case. |
| 767 | C<readdir> returns lowercased filenames, but specifying a file for |
| 768 | opening remains case-insensitive. Files without extensions have a |
| 769 | trailing period on them, so doing a C<readdir> with a file named F<A.;5> |
| 770 | will return F<a.> (though that file could be opened with |
| 771 | C<open(FH, 'A')>). |
| 772 | |
| 773 | RMS had an eight level limit on directory depths from any rooted logical |
| 774 | (allowing 16 levels overall) prior to VMS 7.2. Hence |
| 775 | C<PERL_ROOT:[LIB.2.3.4.5.6.7.8]> is a valid directory specification but |
| 776 | C<PERL_ROOT:[LIB.2.3.4.5.6.7.8.9]> is not. F<Makefile.PL> authors might |
| 777 | have to take this into account, but at least they can refer to the former |
| 778 | as C</PERL_ROOT/lib/2/3/4/5/6/7/8/>. |
| 779 | |
| 780 | The VMS::Filespec module, which gets installed as part of the build |
| 781 | process on VMS, is a pure Perl module that can easily be installed on |
| 782 | non-VMS platforms and can be helpful for conversions to and from RMS |
| 783 | native formats. |
| 784 | |
| 785 | What C<\n> represents depends on the type of file opened. It could |
| 786 | be C<\015>, C<\012>, C<\015\012>, or nothing. Reading from a file |
| 787 | translates newlines to C<\012>, unless C<binmode> was executed on that |
| 788 | handle, just like DOSish perls. |
| 789 | |
| 790 | TCP/IP stacks are optional on VMS, so socket routines might not be |
| 791 | implemented. UDP sockets may not be supported. |
| 792 | |
| 793 | The value of C<$^O> on OpenVMS is "VMS". To determine the architecture |
| 794 | that you are running on without resorting to loading all of C<%Config> |
| 795 | you can examine the content of the C<@INC> array like so: |
| 796 | |
| 797 | if (grep(/VMS_AXP/, @INC)) { |
| 798 | print "I'm on Alpha!\n"; |
| 799 | |
| 800 | } elsif (grep(/VMS_VAX/, @INC)) { |
| 801 | print "I'm on VAX!\n"; |
| 802 | |
| 803 | } else { |
| 804 | print "I'm not so sure about where $^O is...\n"; |
| 805 | } |
| 806 | |
| 807 | On VMS, perl determines the UTC offset from the C<SYS$TIMEZONE_DIFFERENTIAL> |
| 808 | logical name. Although the VMS epoch began at 17-NOV-1858 00:00:00.00, |
| 809 | calls to C<localtime> are adjusted to count offsets from |
| 810 | 01-JAN-1970 00:00:00.00, just like Unix. |
| 811 | |
| 812 | Also see: |
| 813 | |
| 814 | =over 4 |
| 815 | |
| 816 | =item L<perlvms.pod> |
| 817 | |
| 818 | =item vmsperl list, C<majordomo@perl.org> |
| 819 | |
| 820 | Put the words C<subscribe vmsperl> in message body. |
| 821 | |
| 822 | =item vmsperl on the web, C<http://www.sidhe.org/vmsperl/index.html> |
| 823 | |
| 824 | =back |
| 825 | |
| 826 | =head2 VOS |
| 827 | |
| 828 | Perl on VOS is discussed in F<README.vos> in the perl distribution. |
| 829 | Perl on VOS can accept either VOS- or Unix-style file |
| 830 | specifications as in either of the following: |
| 831 | |
| 832 | $ perl -ne "print if /perl_setup/i" >system>notices |
| 833 | $ perl -ne "print if /perl_setup/i" /system/notices |
| 834 | |
| 835 | or even a mixture of both as in: |
| 836 | |
| 837 | $ perl -ne "print if /perl_setup/i" >system/notices |
| 838 | |
| 839 | Even though VOS allows the slash character to appear in object |
| 840 | names, because the VOS port of Perl interprets it as a pathname |
| 841 | delimiting character, VOS files, directories, or links whose names |
| 842 | contain a slash character cannot be processed. Such files must be |
| 843 | renamed before they can be processed by Perl. |
| 844 | |
| 845 | The following C functions are unimplemented on VOS, and any attempt by |
| 846 | Perl to use them will result in a fatal error message and an immediate |
| 847 | exit from Perl: dup, do_aspawn, do_spawn, fork, waitpid. Once these |
| 848 | functions become available in the VOS POSIX.1 implementation, you can |
| 849 | either recompile and rebind Perl, or you can download a newer port from |
| 850 | ftp.stratus.com. |
| 851 | |
| 852 | The value of C<$^O> on VOS is "VOS". To determine the architecture that |
| 853 | you are running on without resorting to loading all of C<%Config> you |
| 854 | can examine the content of the C<@INC> array like so: |
| 855 | |
| 856 | if (grep(/VOS/, @INC)) { |
| 857 | print "I'm on a Stratus box!\n"; |
| 858 | } else { |
| 859 | print "I'm not on a Stratus box!\n"; |
| 860 | die; |
| 861 | } |
| 862 | |
| 863 | if (grep(/860/, @INC)) { |
| 864 | print "This box is a Stratus XA/R!\n"; |
| 865 | |
| 866 | } elsif (grep(/7100/, @INC)) { |
| 867 | print "This box is a Stratus HP 7100 or 8000!\n"; |
| 868 | |
| 869 | } elsif (grep(/8000/, @INC)) { |
| 870 | print "This box is a Stratus HP 8000!\n"; |
| 871 | |
| 872 | } else { |
| 873 | print "This box is a Stratus 68K...\n"; |
| 874 | } |
| 875 | |
| 876 | Also see: |
| 877 | |
| 878 | =over 4 |
| 879 | |
| 880 | =item L<README.vos> |
| 881 | |
| 882 | =item VOS mailing list |
| 883 | |
| 884 | There is no specific mailing list for Perl on VOS. You can post |
| 885 | comments to the comp.sys.stratus newsgroup, or subscribe to the general |
| 886 | Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in |
| 887 | the message body to majordomo@list.stratagy.com. |
| 888 | |
| 889 | =item VOS Perl on the web at C<http://ftp.stratus.com/pub/vos/vos.html> |
| 890 | |
| 891 | =back |
| 892 | |
| 893 | =head2 EBCDIC Platforms |
| 894 | |
| 895 | Recent versions of Perl have been ported to platforms such as OS/400 on |
| 896 | AS/400 minicomputers as well as OS/390 & VM/ESA for IBM Mainframes. Such |
| 897 | computers use EBCDIC character sets internally (usually Character Code |
| 898 | Set ID 00819 for OS/400 and IBM-1047 for OS/390 & VM/ESA). On |
| 899 | the mainframe perl currently works under the "Unix system services |
| 900 | for OS/390" (formerly known as OpenEdition) and VM/ESA OpenEdition. |
| 901 | |
| 902 | As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix |
| 903 | sub-systems do not support the C<#!> shebang trick for script invocation. |
| 904 | Hence, on OS/390 and VM/ESA perl scripts can be executed with a header |
| 905 | similar to the following simple script: |
| 906 | |
| 907 | : # use perl |
| 908 | eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}' |
| 909 | if 0; |
| 910 | #!/usr/local/bin/perl # just a comment really |
| 911 | |
| 912 | print "Hello from perl!\n"; |
| 913 | |
| 914 | On the AS/400, if PERL5 is in your library list, you may need |
| 915 | to wrap your perl scripts in a CL procedure to invoke them like so: |
| 916 | |
| 917 | BEGIN |
| 918 | CALL PGM(PERL5/PERL) PARM('/QOpenSys/hello.pl') |
| 919 | ENDPGM |
| 920 | |
| 921 | This will invoke the perl script F<hello.pl> in the root of the |
| 922 | QOpenSys file system. On the AS/400 calls to C<system> or backticks |
| 923 | must use CL syntax. |
| 924 | |
| 925 | On these platforms, bear in mind that the EBCDIC character set may have |
| 926 | an effect on what happens with some perl functions (such as C<chr>, |
| 927 | C<pack>, C<print>, C<printf>, C<ord>, C<sort>, C<sprintf>, C<unpack>), as |
| 928 | well as bit-fiddling with ASCII constants using operators like C<^>, C<&> |
| 929 | and C<|>, not to mention dealing with socket interfaces to ASCII computers |
| 930 | (see L<"Newlines">). |
| 931 | |
| 932 | Fortunately, most web servers for the mainframe will correctly |
| 933 | translate the C<\n> in the following statement to its ASCII equivalent |
| 934 | (C<\r> is the same under both Unix and OS/390 & VM/ESA): |
| 935 | |
| 936 | print "Content-type: text/html\r\n\r\n"; |
| 937 | |
| 938 | The value of C<$^O> on OS/390 is "os390". |
| 939 | |
| 940 | The value of C<$^O> on VM/ESA is "vmesa". |
| 941 | |
| 942 | Some simple tricks for determining if you are running on an EBCDIC |
| 943 | platform could include any of the following (perhaps all): |
| 944 | |
| 945 | if ("\t" eq "\05") { print "EBCDIC may be spoken here!\n"; } |
| 946 | |
| 947 | if (ord('A') == 193) { print "EBCDIC may be spoken here!\n"; } |
| 948 | |
| 949 | if (chr(169) eq 'z') { print "EBCDIC may be spoken here!\n"; } |
| 950 | |
| 951 | One thing you may not want to rely on is the EBCDIC encoding |
| 952 | of punctuation characters since these may differ from code page to code |
| 953 | page (and once your module or script is rumoured to work with EBCDIC, |
| 954 | folks will want it to work with all EBCDIC character sets). |
| 955 | |
| 956 | Also see: |
| 957 | |
| 958 | =over 4 |
| 959 | |
| 960 | =item perl-mvs list |
| 961 | |
| 962 | The perl-mvs@perl.org list is for discussion of porting issues as well as |
| 963 | general usage issues for all EBCDIC Perls. Send a message body of |
| 964 | "subscribe perl-mvs" to majordomo@perl.org. |
| 965 | |
| 966 | =item AS/400 Perl information at C<http://as400.rochester.ibm.com/> |
| 967 | |
| 968 | =back |
| 969 | |
| 970 | =head2 Acorn RISC OS |
| 971 | |
| 972 | Because Acorns use ASCII with newlines (C<\n>) in text files as C<\012> like |
| 973 | Unix, and because Unix filename emulation is turned on by default, |
| 974 | most simple scripts will probably work "out of the box". The native |
| 975 | filesystem is modular, and individual filesystems are free to be |
| 976 | case-sensitive or insensitive, and are usually case-preserving. Some |
| 977 | native filesystems have name length limits, which file and directory |
| 978 | names are silently truncated to fit. Scripts should be aware that the |
| 979 | standard filesystem currently has a name length limit of B<10> |
| 980 | characters, with up to 77 items in a directory, but other filesystems |
| 981 | may not impose such limitations. |
| 982 | |
| 983 | Native filenames are of the form |
| 984 | |
| 985 | Filesystem#Special_Field::DiskName.$.Directory.Directory.File |
| 986 | |
| 987 | where |
| 988 | |
| 989 | Special_Field is not usually present, but may contain . and $ . |
| 990 | Filesystem =~ m|[A-Za-z0-9_]| |
| 991 | DsicName =~ m|[A-Za-z0-9_/]| |
| 992 | $ represents the root directory |
| 993 | . is the path separator |
| 994 | @ is the current directory (per filesystem but machine global) |
| 995 | ^ is the parent directory |
| 996 | Directory and File =~ m|[^\0- "\.\$\%\&:\@\\^\|\177]+| |
| 997 | |
| 998 | The default filename translation is roughly C<tr|/.|./|;> |
| 999 | |
| 1000 | Note that C<"ADFS::HardDisk.$.File" ne 'ADFS::HardDisk.$.File'> and that |
| 1001 | the second stage of C<$> interpolation in regular expressions will fall |
| 1002 | foul of the C<$.> if scripts are not careful. |
| 1003 | |
| 1004 | Logical paths specified by system variables containing comma-separated |
| 1005 | search lists are also allowed; hence C<System:Modules> is a valid |
| 1006 | filename, and the filesystem will prefix C<Modules> with each section of |
| 1007 | C<System$Path> until a name is made that points to an object on disk. |
| 1008 | Writing to a new file C<System:Modules> would be allowed only if |
| 1009 | C<System$Path> contains a single item list. The filesystem will also |
| 1010 | expand system variables in filenames if enclosed in angle brackets, so |
| 1011 | C<E<lt>System$DirE<gt>.Modules> would look for the file |
| 1012 | S<C<$ENV{'System$Dir'} . 'Modules'>>. The obvious implication of this is |
| 1013 | that B<fully qualified filenames can start with C<E<lt>E<gt>>> and should |
| 1014 | be protected when C<open> is used for input. |
| 1015 | |
| 1016 | Because C<.> was in use as a directory separator and filenames could not |
| 1017 | be assumed to be unique after 10 characters, Acorn implemented the C |
| 1018 | compiler to strip the trailing C<.c> C<.h> C<.s> and C<.o> suffix from |
| 1019 | filenames specified in source code and store the respective files in |
| 1020 | subdirectories named after the suffix. Hence files are translated: |
| 1021 | |
| 1022 | foo.h h.foo |
| 1023 | C:foo.h C:h.foo (logical path variable) |
| 1024 | sys/os.h sys.h.os (C compiler groks Unix-speak) |
| 1025 | 10charname.c c.10charname |
| 1026 | 10charname.o o.10charname |
| 1027 | 11charname_.c c.11charname (assuming filesystem truncates at 10) |
| 1028 | |
| 1029 | The Unix emulation library's translation of filenames to native assumes |
| 1030 | that this sort of translation is required, and it allows a user-defined list |
| 1031 | of known suffixes that it will transpose in this fashion. This may |
| 1032 | seem transparent, but consider that with these rules C<foo/bar/baz.h> |
| 1033 | and C<foo/bar/h/baz> both map to C<foo.bar.h.baz>, and that C<readdir> and |
| 1034 | C<glob> cannot and do not attempt to emulate the reverse mapping. Other |
| 1035 | C<.>'s in filenames are translated to C</>. |
| 1036 | |
| 1037 | As implied above, the environment accessed through C<%ENV> is global, and |
| 1038 | the convention is that program specific environment variables are of the |
| 1039 | form C<Program$Name>. Each filesystem maintains a current directory, |
| 1040 | and the current filesystem's current directory is the B<global> current |
| 1041 | directory. Consequently, sociable programs don't change the current |
| 1042 | directory but rely on full pathnames, and programs (and Makefiles) cannot |
| 1043 | assume that they can spawn a child process which can change the current |
| 1044 | directory without affecting its parent (and everyone else for that |
| 1045 | matter). |
| 1046 | |
| 1047 | Because native operating system filehandles are global and are currently |
| 1048 | allocated down from 255, with 0 being a reserved value, the Unix emulation |
| 1049 | library emulates Unix filehandles. Consequently, you can't rely on |
| 1050 | passing C<STDIN>, C<STDOUT>, or C<STDERR> to your children. |
| 1051 | |
| 1052 | The desire of users to express filenames of the form |
| 1053 | C<E<lt>Foo$DirE<gt>.Bar> on the command line unquoted causes problems, |
| 1054 | too: C<``> command output capture has to perform a guessing game. It |
| 1055 | assumes that a string C<E<lt>[^E<lt>E<gt>]+\$[^E<lt>E<gt>]E<gt>> is a |
| 1056 | reference to an environment variable, whereas anything else involving |
| 1057 | C<E<lt>> or C<E<gt>> is redirection, and generally manages to be 99% |
| 1058 | right. Of course, the problem remains that scripts cannot rely on any |
| 1059 | Unix tools being available, or that any tools found have Unix-like command |
| 1060 | line arguments. |
| 1061 | |
| 1062 | Extensions and XS are, in theory, buildable by anyone using free |
| 1063 | tools. In practice, many don't, as users of the Acorn platform are |
| 1064 | used to binary distributions. MakeMaker does run, but no available |
| 1065 | make currently copes with MakeMaker's makefiles; even if and when |
| 1066 | this should be fixed, the lack of a Unix-like shell will cause |
| 1067 | problems with makefile rules, especially lines of the form C<cd |
| 1068 | sdbm && make all>, and anything using quoting. |
| 1069 | |
| 1070 | "S<RISC OS>" is the proper name for the operating system, but the value |
| 1071 | in C<$^O> is "riscos" (because we don't like shouting). |
| 1072 | |
| 1073 | =head2 Other perls |
| 1074 | |
| 1075 | Perl has been ported to many platforms that do not fit into any of |
| 1076 | the categories listed above. Some, such as AmigaOS, Atari MiNT, |
| 1077 | BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated |
| 1078 | into the standard Perl source code kit. You may need to see the |
| 1079 | F<ports/> directory on CPAN for information, and possibly binaries, |
| 1080 | for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware, |
| 1081 | Tandem Guardian, I<etc.> (Yes, we know that some of these OSes may |
| 1082 | fall under the Unix category, but we are not a standards body.) |
| 1083 | |
| 1084 | See also: |
| 1085 | |
| 1086 | =over 4 |
| 1087 | |
| 1088 | =item Atari, Guido Flohr's page C<http://stud.uni-sb.de/~gufl0000/> |
| 1089 | |
| 1090 | =item HP 300 MPE/iX C<http://www.cccd.edu/~markb/perlix.html> |
| 1091 | |
| 1092 | =item Novell Netware |
| 1093 | |
| 1094 | A free perl5-based PERL.NLM for Novell Netware is available in |
| 1095 | precompiled binary and source code form from C<http://www.novell.com/> |
| 1096 | as well as from CPAN. |
| 1097 | |
| 1098 | =back |
| 1099 | |
| 1100 | =head1 FUNCTION IMPLEMENTATIONS |
| 1101 | |
| 1102 | Listed below are functions that are either completely unimplemented |
| 1103 | or else have been implemented differently on various platforms. |
| 1104 | Following each description will be, in parentheses, a list of |
| 1105 | platforms that the description applies to. |
| 1106 | |
| 1107 | The list may well be incomplete, or even wrong in some places. When |
| 1108 | in doubt, consult the platform-specific README files in the Perl |
| 1109 | source distribution, and any other documentation resources accompanying |
| 1110 | a given port. |
| 1111 | |
| 1112 | Be aware, moreover, that even among Unix-ish systems there are variations. |
| 1113 | |
| 1114 | For many functions, you can also query C<%Config>, exported by |
| 1115 | default from the Config module. For example, to check whether the |
| 1116 | platform has the C<lstat> call, check C<$Config{d_lstat}>. See |
| 1117 | L<Config> for a full description of available variables. |
| 1118 | |
| 1119 | =head2 Alphabetical Listing of Perl Functions |
| 1120 | |
| 1121 | =over 8 |
| 1122 | |
| 1123 | =item -X FILEHANDLE |
| 1124 | |
| 1125 | =item -X EXPR |
| 1126 | |
| 1127 | =item -X |
| 1128 | |
| 1129 | C<-r>, C<-w>, and C<-x> have a limited meaning only; directories |
| 1130 | and applications are executable, and there are no uid/gid |
| 1131 | considerations. C<-o> is not supported. (S<Mac OS>) |
| 1132 | |
| 1133 | C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible, |
| 1134 | which may not reflect UIC-based file protections. (VMS) |
| 1135 | |
| 1136 | C<-s> returns the size of the data fork, not the total size of data fork |
| 1137 | plus resource fork. (S<Mac OS>). |
| 1138 | |
| 1139 | C<-s> by name on an open file will return the space reserved on disk, |
| 1140 | rather than the current extent. C<-s> on an open filehandle returns the |
| 1141 | current size. (S<RISC OS>) |
| 1142 | |
| 1143 | C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>, |
| 1144 | C<-x>, C<-o>. (S<Mac OS>, Win32, VMS, S<RISC OS>) |
| 1145 | |
| 1146 | C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented. |
| 1147 | (S<Mac OS>) |
| 1148 | |
| 1149 | C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful. |
| 1150 | (Win32, VMS, S<RISC OS>) |
| 1151 | |
| 1152 | C<-d> is true if passed a device spec without an explicit directory. |
| 1153 | (VMS) |
| 1154 | |
| 1155 | C<-T> and C<-B> are implemented, but might misclassify Mac text files |
| 1156 | with foreign characters; this is the case will all platforms, but may |
| 1157 | affect S<Mac OS> often. (S<Mac OS>) |
| 1158 | |
| 1159 | C<-x> (or C<-X>) determine if a file ends in one of the executable |
| 1160 | suffixes. C<-S> is meaningless. (Win32) |
| 1161 | |
| 1162 | C<-x> (or C<-X>) determine if a file has an executable file type. |
| 1163 | (S<RISC OS>) |
| 1164 | |
| 1165 | =item binmode FILEHANDLE |
| 1166 | |
| 1167 | Meaningless. (S<Mac OS>, S<RISC OS>) |
| 1168 | |
| 1169 | Reopens file and restores pointer; if function fails, underlying |
| 1170 | filehandle may be closed, or pointer may be in a different position. |
| 1171 | (VMS) |
| 1172 | |
| 1173 | The value returned by C<tell> may be affected after the call, and |
| 1174 | the filehandle may be flushed. (Win32) |
| 1175 | |
| 1176 | =item chmod LIST |
| 1177 | |
| 1178 | Only limited meaning. Disabling/enabling write permission is mapped to |
| 1179 | locking/unlocking the file. (S<Mac OS>) |
| 1180 | |
| 1181 | Only good for changing "owner" read-write access, "group", and "other" |
| 1182 | bits are meaningless. (Win32) |
| 1183 | |
| 1184 | Only good for changing "owner" and "other" read-write access. (S<RISC OS>) |
| 1185 | |
| 1186 | Access permissions are mapped onto VOS access-control list changes. (VOS) |
| 1187 | |
| 1188 | =item chown LIST |
| 1189 | |
| 1190 | Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>, VOS) |
| 1191 | |
| 1192 | Does nothing, but won't fail. (Win32) |
| 1193 | |
| 1194 | =item chroot FILENAME |
| 1195 | |
| 1196 | =item chroot |
| 1197 | |
| 1198 | Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS, VM/ESA) |
| 1199 | |
| 1200 | =item crypt PLAINTEXT,SALT |
| 1201 | |
| 1202 | May not be available if library or source was not provided when building |
| 1203 | perl. (Win32) |
| 1204 | |
| 1205 | Not implemented. (VOS) |
| 1206 | |
| 1207 | =item dbmclose HASH |
| 1208 | |
| 1209 | Not implemented. (VMS, Plan9, VOS) |
| 1210 | |
| 1211 | =item dbmopen HASH,DBNAME,MODE |
| 1212 | |
| 1213 | Not implemented. (VMS, Plan9, VOS) |
| 1214 | |
| 1215 | =item dump LABEL |
| 1216 | |
| 1217 | Not useful. (S<Mac OS>, S<RISC OS>) |
| 1218 | |
| 1219 | Not implemented. (Win32) |
| 1220 | |
| 1221 | Invokes VMS debugger. (VMS) |
| 1222 | |
| 1223 | =item exec LIST |
| 1224 | |
| 1225 | Not implemented. (S<Mac OS>) |
| 1226 | |
| 1227 | Implemented via Spawn. (VM/ESA) |
| 1228 | |
| 1229 | =item fcntl FILEHANDLE,FUNCTION,SCALAR |
| 1230 | |
| 1231 | Not implemented. (Win32, VMS) |
| 1232 | |
| 1233 | =item flock FILEHANDLE,OPERATION |
| 1234 | |
| 1235 | Not implemented (S<Mac OS>, VMS, S<RISC OS>, VOS). |
| 1236 | |
| 1237 | Available only on Windows NT (not on Windows 95). (Win32) |
| 1238 | |
| 1239 | =item fork |
| 1240 | |
| 1241 | Not implemented. (S<Mac OS>, Win32, AmigaOS, S<RISC OS>, VOS, VM/ESA) |
| 1242 | |
| 1243 | =item getlogin |
| 1244 | |
| 1245 | Not implemented. (S<Mac OS>, S<RISC OS>) |
| 1246 | |
| 1247 | =item getpgrp PID |
| 1248 | |
| 1249 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS) |
| 1250 | |
| 1251 | =item getppid |
| 1252 | |
| 1253 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>) |
| 1254 | |
| 1255 | =item getpriority WHICH,WHO |
| 1256 | |
| 1257 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA) |
| 1258 | |
| 1259 | =item getpwnam NAME |
| 1260 | |
| 1261 | Not implemented. (S<Mac OS>, Win32) |
| 1262 | |
| 1263 | Not useful. (S<RISC OS>) |
| 1264 | |
| 1265 | =item getgrnam NAME |
| 1266 | |
| 1267 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>) |
| 1268 | |
| 1269 | =item getnetbyname NAME |
| 1270 | |
| 1271 | Not implemented. (S<Mac OS>, Win32, Plan9) |
| 1272 | |
| 1273 | =item getpwuid UID |
| 1274 | |
| 1275 | Not implemented. (S<Mac OS>, Win32) |
| 1276 | |
| 1277 | Not useful. (S<RISC OS>) |
| 1278 | |
| 1279 | =item getgrgid GID |
| 1280 | |
| 1281 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>) |
| 1282 | |
| 1283 | =item getnetbyaddr ADDR,ADDRTYPE |
| 1284 | |
| 1285 | Not implemented. (S<Mac OS>, Win32, Plan9) |
| 1286 | |
| 1287 | =item getprotobynumber NUMBER |
| 1288 | |
| 1289 | Not implemented. (S<Mac OS>) |
| 1290 | |
| 1291 | =item getservbyport PORT,PROTO |
| 1292 | |
| 1293 | Not implemented. (S<Mac OS>) |
| 1294 | |
| 1295 | =item getpwent |
| 1296 | |
| 1297 | Not implemented. (S<Mac OS>, Win32, VM/ESA) |
| 1298 | |
| 1299 | =item getgrent |
| 1300 | |
| 1301 | Not implemented. (S<Mac OS>, Win32, VMS, VM/ESA) |
| 1302 | |
| 1303 | =item gethostent |
| 1304 | |
| 1305 | Not implemented. (S<Mac OS>, Win32) |
| 1306 | |
| 1307 | =item getnetent |
| 1308 | |
| 1309 | Not implemented. (S<Mac OS>, Win32, Plan9) |
| 1310 | |
| 1311 | =item getprotoent |
| 1312 | |
| 1313 | Not implemented. (S<Mac OS>, Win32, Plan9) |
| 1314 | |
| 1315 | =item getservent |
| 1316 | |
| 1317 | Not implemented. (Win32, Plan9) |
| 1318 | |
| 1319 | =item setpwent |
| 1320 | |
| 1321 | Not implemented. (S<Mac OS>, Win32, S<RISC OS>) |
| 1322 | |
| 1323 | =item setgrent |
| 1324 | |
| 1325 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>) |
| 1326 | |
| 1327 | =item sethostent STAYOPEN |
| 1328 | |
| 1329 | Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>) |
| 1330 | |
| 1331 | =item setnetent STAYOPEN |
| 1332 | |
| 1333 | Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>) |
| 1334 | |
| 1335 | =item setprotoent STAYOPEN |
| 1336 | |
| 1337 | Not implemented. (S<Mac OS>, Win32, Plan9, S<RISC OS>) |
| 1338 | |
| 1339 | =item setservent STAYOPEN |
| 1340 | |
| 1341 | Not implemented. (Plan9, Win32, S<RISC OS>) |
| 1342 | |
| 1343 | =item endpwent |
| 1344 | |
| 1345 | Not implemented. (S<Mac OS>, Win32, VM/ESA) |
| 1346 | |
| 1347 | =item endgrent |
| 1348 | |
| 1349 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VM/ESA) |
| 1350 | |
| 1351 | =item endhostent |
| 1352 | |
| 1353 | Not implemented. (S<Mac OS>, Win32) |
| 1354 | |
| 1355 | =item endnetent |
| 1356 | |
| 1357 | Not implemented. (S<Mac OS>, Win32, Plan9) |
| 1358 | |
| 1359 | =item endprotoent |
| 1360 | |
| 1361 | Not implemented. (S<Mac OS>, Win32, Plan9) |
| 1362 | |
| 1363 | =item endservent |
| 1364 | |
| 1365 | Not implemented. (Plan9, Win32) |
| 1366 | |
| 1367 | =item getsockopt SOCKET,LEVEL,OPTNAME |
| 1368 | |
| 1369 | Not implemented. (S<Mac OS>, Plan9) |
| 1370 | |
| 1371 | =item glob EXPR |
| 1372 | |
| 1373 | =item glob |
| 1374 | |
| 1375 | Globbing built-in, but only C<*> and C<?> metacharacters are supported. |
| 1376 | (S<Mac OS>) |
| 1377 | |
| 1378 | Features depend on external perlglob.exe or perlglob.bat. May be |
| 1379 | overridden with something like File::DosGlob, which is recommended. |
| 1380 | (Win32) |
| 1381 | |
| 1382 | Globbing built-in, but only C<*> and C<?> metacharacters are supported. |
| 1383 | Globbing relies on operating system calls, which may return filenames |
| 1384 | in any order. As most filesystems are case-insensitive, even "sorted" |
| 1385 | filenames will not be in case-sensitive order. (S<RISC OS>) |
| 1386 | |
| 1387 | =item ioctl FILEHANDLE,FUNCTION,SCALAR |
| 1388 | |
| 1389 | Not implemented. (VMS) |
| 1390 | |
| 1391 | Available only for socket handles, and it does what the ioctlsocket() call |
| 1392 | in the Winsock API does. (Win32) |
| 1393 | |
| 1394 | Available only for socket handles. (S<RISC OS>) |
| 1395 | |
| 1396 | =item kill LIST |
| 1397 | |
| 1398 | Not implemented, hence not useful for taint checking. (S<Mac OS>, |
| 1399 | S<RISC OS>) |
| 1400 | |
| 1401 | Available only for process handles returned by the C<system(1, ...)> |
| 1402 | method of spawning a process. (Win32) |
| 1403 | |
| 1404 | =item link OLDFILE,NEWFILE |
| 1405 | |
| 1406 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>) |
| 1407 | |
| 1408 | Link count not updated because hard links are not quite that hard |
| 1409 | (They are sort of half-way between hard and soft links). (AmigaOS) |
| 1410 | |
| 1411 | =item lstat FILEHANDLE |
| 1412 | |
| 1413 | =item lstat EXPR |
| 1414 | |
| 1415 | =item lstat |
| 1416 | |
| 1417 | Not implemented. (VMS, S<RISC OS>) |
| 1418 | |
| 1419 | Return values may be bogus. (Win32) |
| 1420 | |
| 1421 | =item msgctl ID,CMD,ARG |
| 1422 | |
| 1423 | =item msgget KEY,FLAGS |
| 1424 | |
| 1425 | =item msgsnd ID,MSG,FLAGS |
| 1426 | |
| 1427 | =item msgrcv ID,VAR,SIZE,TYPE,FLAGS |
| 1428 | |
| 1429 | Not implemented. (S<Mac OS>, Win32, VMS, Plan9, S<RISC OS>, VOS) |
| 1430 | |
| 1431 | =item open FILEHANDLE,EXPR |
| 1432 | |
| 1433 | =item open FILEHANDLE |
| 1434 | |
| 1435 | The C<|> variants are supported only if ToolServer is installed. |
| 1436 | (S<Mac OS>) |
| 1437 | |
| 1438 | open to C<|-> and C<-|> are unsupported. (S<Mac OS>, Win32, S<RISC OS>) |
| 1439 | |
| 1440 | =item pipe READHANDLE,WRITEHANDLE |
| 1441 | |
| 1442 | Not implemented. (S<Mac OS>) |
| 1443 | |
| 1444 | Very limited functionality. (MiNT) |
| 1445 | |
| 1446 | =item readlink EXPR |
| 1447 | |
| 1448 | =item readlink |
| 1449 | |
| 1450 | Not implemented. (Win32, VMS, S<RISC OS>) |
| 1451 | |
| 1452 | =item select RBITS,WBITS,EBITS,TIMEOUT |
| 1453 | |
| 1454 | Only implemented on sockets. (Win32) |
| 1455 | |
| 1456 | Only reliable on sockets. (S<RISC OS>) |
| 1457 | |
| 1458 | =item semctl ID,SEMNUM,CMD,ARG |
| 1459 | |
| 1460 | =item semget KEY,NSEMS,FLAGS |
| 1461 | |
| 1462 | =item semop KEY,OPSTRING |
| 1463 | |
| 1464 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS) |
| 1465 | |
| 1466 | =item setpgrp PID,PGRP |
| 1467 | |
| 1468 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS) |
| 1469 | |
| 1470 | =item setpriority WHICH,WHO,PRIORITY |
| 1471 | |
| 1472 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS) |
| 1473 | |
| 1474 | =item setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL |
| 1475 | |
| 1476 | Not implemented. (S<Mac OS>, Plan9) |
| 1477 | |
| 1478 | =item shmctl ID,CMD,ARG |
| 1479 | |
| 1480 | =item shmget KEY,SIZE,FLAGS |
| 1481 | |
| 1482 | =item shmread ID,VAR,POS,SIZE |
| 1483 | |
| 1484 | =item shmwrite ID,STRING,POS,SIZE |
| 1485 | |
| 1486 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS) |
| 1487 | |
| 1488 | =item socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL |
| 1489 | |
| 1490 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA) |
| 1491 | |
| 1492 | =item stat FILEHANDLE |
| 1493 | |
| 1494 | =item stat EXPR |
| 1495 | |
| 1496 | =item stat |
| 1497 | |
| 1498 | mtime and atime are the same thing, and ctime is creation time instead of |
| 1499 | inode change time. (S<Mac OS>) |
| 1500 | |
| 1501 | device and inode are not meaningful. (Win32) |
| 1502 | |
| 1503 | device and inode are not necessarily reliable. (VMS) |
| 1504 | |
| 1505 | mtime, atime and ctime all return the last modification time. Device and |
| 1506 | inode are not necessarily reliable. (S<RISC OS>) |
| 1507 | |
| 1508 | =item symlink OLDFILE,NEWFILE |
| 1509 | |
| 1510 | Not implemented. (Win32, VMS, S<RISC OS>) |
| 1511 | |
| 1512 | =item syscall LIST |
| 1513 | |
| 1514 | Not implemented. (S<Mac OS>, Win32, VMS, S<RISC OS>, VOS, VM/ESA) |
| 1515 | |
| 1516 | =item sysopen FILEHANDLE,FILENAME,MODE,PERMS |
| 1517 | |
| 1518 | The traditional "0", "1", and "2" MODEs are implemented with different |
| 1519 | numeric values on some systems. The flags exported by C<Fcntl> |
| 1520 | (O_RDONLY, O_WRONLY, O_RDWR) should work everywhere though. (S<Mac |
| 1521 | OS>, OS/390, VM/ESA) |
| 1522 | |
| 1523 | =item system LIST |
| 1524 | |
| 1525 | Only implemented if ToolServer is installed. (S<Mac OS>) |
| 1526 | |
| 1527 | As an optimization, may not call the command shell specified in |
| 1528 | C<$ENV{PERL5SHELL}>. C<system(1, @args)> spawns an external |
| 1529 | process and immediately returns its process designator, without |
| 1530 | waiting for it to terminate. Return value may be used subsequently |
| 1531 | in C<wait> or C<waitpid>. (Win32) |
| 1532 | |
| 1533 | There is no shell to process metacharacters, and the native standard is |
| 1534 | to pass a command line terminated by "\n" "\r" or "\0" to the spawned |
| 1535 | program. Redirection such as C<E<gt> foo> is performed (if at all) by |
| 1536 | the run time library of the spawned program. C<system> I<list> will call |
| 1537 | the Unix emulation library's C<exec> emulation, which attempts to provide |
| 1538 | emulation of the stdin, stdout, stderr in force in the parent, providing |
| 1539 | the child program uses a compatible version of the emulation library. |
| 1540 | I<scalar> will call the native command line direct and no such emulation |
| 1541 | of a child Unix program will exists. Mileage B<will> vary. (S<RISC OS>) |
| 1542 | |
| 1543 | Far from being POSIX compliant. Because there may be no underlying |
| 1544 | /bin/sh tries to work around the problem by forking and execing the |
| 1545 | first token in its argument string. Handles basic redirection |
| 1546 | ("E<lt>" or "E<gt>") on its own behalf. (MiNT) |
| 1547 | |
| 1548 | =item times |
| 1549 | |
| 1550 | Only the first entry returned is nonzero. (S<Mac OS>) |
| 1551 | |
| 1552 | "cumulative" times will be bogus. On anything other than Windows NT, |
| 1553 | "system" time will be bogus, and "user" time is actually the time |
| 1554 | returned by the clock() function in the C runtime library. (Win32) |
| 1555 | |
| 1556 | Not useful. (S<RISC OS>) |
| 1557 | |
| 1558 | =item truncate FILEHANDLE,LENGTH |
| 1559 | |
| 1560 | =item truncate EXPR,LENGTH |
| 1561 | |
| 1562 | Not implemented. (VMS) |
| 1563 | |
| 1564 | Truncation to zero-length only. (VOS) |
| 1565 | |
| 1566 | If a FILEHANDLE is supplied, it must be writable and opened in append |
| 1567 | mode (i.e., use C<open(FH, '>>filename')> |
| 1568 | or C<sysopen(FH,...,O_APPEND|O_RDWR)>. If a filename is supplied, it |
| 1569 | should not be held open elsewhere. (Win32) |
| 1570 | |
| 1571 | =item umask EXPR |
| 1572 | |
| 1573 | =item umask |
| 1574 | |
| 1575 | Returns undef where unavailable, as of version 5.005. |
| 1576 | |
| 1577 | C<umask> works but the correct permissions are set only when the file |
| 1578 | is finally closed. (AmigaOS) |
| 1579 | |
| 1580 | =item utime LIST |
| 1581 | |
| 1582 | Only the modification time is updated. (S<Mac OS>, VMS, S<RISC OS>) |
| 1583 | |
| 1584 | May not behave as expected. Behavior depends on the C runtime |
| 1585 | library's implementation of utime(), and the filesystem being |
| 1586 | used. The FAT filesystem typically does not support an "access |
| 1587 | time" field, and it may limit timestamps to a granularity of |
| 1588 | two seconds. (Win32) |
| 1589 | |
| 1590 | =item wait |
| 1591 | |
| 1592 | =item waitpid PID,FLAGS |
| 1593 | |
| 1594 | Not implemented. (S<Mac OS>, VOS) |
| 1595 | |
| 1596 | Can only be applied to process handles returned for processes spawned |
| 1597 | using C<system(1, ...)>. (Win32) |
| 1598 | |
| 1599 | Not useful. (S<RISC OS>) |
| 1600 | |
| 1601 | =back |
| 1602 | |
| 1603 | =head1 CHANGES |
| 1604 | |
| 1605 | =over 4 |
| 1606 | |
| 1607 | =item v1.43, 24 May 1999 |
| 1608 | |
| 1609 | Added a lot of cleaning up from Tom Christiansen. |
| 1610 | |
| 1611 | =item v1.42, 22 May 1999 |
| 1612 | |
| 1613 | Added notes about tests, sprintf/printf, and epoch offsets. |
| 1614 | |
| 1615 | =item v1.41, 19 May 1999 |
| 1616 | |
| 1617 | Lots more little changes to formatting and content. |
| 1618 | |
| 1619 | Added a bunch of <$^O> and related values |
| 1620 | for various platforms; fixed mail and web addresses, and added |
| 1621 | and changed miscellaneous notes. (Peter Prymmer) |
| 1622 | |
| 1623 | =item v1.40, 11 April 1999 |
| 1624 | |
| 1625 | Miscellaneous changes. |
| 1626 | |
| 1627 | =item v1.39, 11 February 1999 |
| 1628 | |
| 1629 | Changes from Jarkko and EMX URL fixes Michael Schwern. Additional |
| 1630 | note about newlines added. |
| 1631 | |
| 1632 | =item v1.38, 31 December 1998 |
| 1633 | |
| 1634 | More changes from Jarkko. |
| 1635 | |
| 1636 | =item v1.37, 19 December 1998 |
| 1637 | |
| 1638 | More minor changes. Merge two separate version 1.35 documents. |
| 1639 | |
| 1640 | =item v1.36, 9 September 1998 |
| 1641 | |
| 1642 | Updated for Stratus VOS. Also known as version 1.35. |
| 1643 | |
| 1644 | =item v1.35, 13 August 1998 |
| 1645 | |
| 1646 | Integrate more minor changes, plus addition of new sections under |
| 1647 | L<"ISSUES">: L<"Numbers endianness and Width">, |
| 1648 | L<"Character sets and character encoding">, |
| 1649 | L<"Internationalisation">. |
| 1650 | |
| 1651 | =item v1.33, 06 August 1998 |
| 1652 | |
| 1653 | Integrate more minor changes. |
| 1654 | |
| 1655 | =item v1.32, 05 August 1998 |
| 1656 | |
| 1657 | Integrate more minor changes. |
| 1658 | |
| 1659 | =item v1.30, 03 August 1998 |
| 1660 | |
| 1661 | Major update for RISC OS, other minor changes. |
| 1662 | |
| 1663 | =item v1.23, 10 July 1998 |
| 1664 | |
| 1665 | First public release with perl5.005. |
| 1666 | |
| 1667 | =back |
| 1668 | |
| 1669 | =head1 AUTHORS / CONTRIBUTORS |
| 1670 | |
| 1671 | Abigail E<lt>abigail@fnx.comE<gt>, |
| 1672 | Charles Bailey E<lt>bailey@newman.upenn.eduE<gt>, |
| 1673 | Graham Barr E<lt>gbarr@pobox.comE<gt>, |
| 1674 | Tom Christiansen E<lt>tchrist@perl.comE<gt>, |
| 1675 | Nicholas Clark E<lt>Nicholas.Clark@liverpool.ac.ukE<gt>, |
| 1676 | Andy Dougherty E<lt>doughera@lafcol.lafayette.eduE<gt>, |
| 1677 | Dominic Dunlop E<lt>domo@vo.luE<gt>, |
| 1678 | Neale Ferguson E<lt>neale@mailbox.tabnsw.com.auE<gt> |
| 1679 | Paul Green E<lt>Paul_Green@stratus.comE<gt>, |
| 1680 | M.J.T. Guy E<lt>mjtg@cus.cam.ac.ukE<gt>, |
| 1681 | Jarkko Hietaniemi E<lt>jhi@iki.fi<gt>, |
| 1682 | Luther Huffman E<lt>lutherh@stratcom.comE<gt>, |
| 1683 | Nick Ing-Simmons E<lt>nick@ni-s.u-net.comE<gt>, |
| 1684 | Andreas J. KE<ouml>nig E<lt>koenig@kulturbox.deE<gt>, |
| 1685 | Markus Laker E<lt>mlaker@contax.co.ukE<gt>, |
| 1686 | Andrew M. Langmead E<lt>aml@world.std.comE<gt>, |
| 1687 | Larry Moore E<lt>ljmoore@freespace.netE<gt>, |
| 1688 | Paul Moore E<lt>Paul.Moore@uk.origin-it.comE<gt>, |
| 1689 | Chris Nandor E<lt>pudge@pobox.comE<gt>, |
| 1690 | Matthias Neeracher E<lt>neeri@iis.ee.ethz.chE<gt>, |
| 1691 | Gary Ng E<lt>71564.1743@CompuServe.COME<gt>, |
| 1692 | Tom Phoenix E<lt>rootbeer@teleport.comE<gt>, |
| 1693 | Peter Prymmer E<lt>pvhp@forte.comE<gt>, |
| 1694 | Hugo van der Sanden E<lt>hv@crypt0.demon.co.ukE<gt>, |
| 1695 | Gurusamy Sarathy E<lt>gsar@umich.eduE<gt>, |
| 1696 | Paul J. Schinder E<lt>schinder@pobox.comE<gt>, |
| 1697 | Michael G Schwern E<lt>schwern@pobox.comE<gt>, |
| 1698 | Dan Sugalski E<lt>sugalskd@ous.eduE<gt>, |
| 1699 | Nathan Torkington E<lt>gnat@frii.comE<gt>. |
| 1700 | |
| 1701 | This document is maintained by Chris Nandor |
| 1702 | E<lt>pudge@pobox.comE<gt>. |
| 1703 | |
| 1704 | =head1 VERSION |
| 1705 | |
| 1706 | Version 1.43, last modified 24 May 1999 |