1 =head1 Notes on Perl 5 for VMS
3 Gathered below are notes describing details of Perl 5's
4 behavior on VMS. They are a supplement to the regular Perl 5
5 documentation, so we have focussed on the ways in which Perl
6 5 functions differently under VMS than it does under Unix,
7 and on the interactions between Perl and the rest of the
8 operating system. We haven't tried to duplicate complete
9 descriptions of Perl features from the main Perl
10 documentation, which can be found in the F<[.pod]>
11 subdirectory of the Perl distribution.
13 We hope these notes will save you from confusion and lost
14 sleep when writing Perl scripts on VMS. If you find we've
15 missed something you think should appear here, please don't
16 hesitate to drop a line to vmsperl@genetics.upenn.edu.
18 =head1 Organization of Perl
22 During the installation process, three Perl images are produced.
23 F<Miniperl.Exe> is an executable image which contains all of
24 the basic functionality of Perl, but cannot take advantage of
25 Perl extensions. It is used to generate several files needed
26 to build the complete Perl and various extensions. Once you've
27 finished installing Perl, you can delete this image.
29 Most of the complete Perl resides in the shareable image
30 F<PerlShr.Exe>, which provides a core to which the Perl executable
31 image and all Perl extensions are linked. You should place this
32 image in F<Sys$Share>, or define the logical name F<PerlShr> to
33 translate to the full file specification of this image. It should
34 be world readable. (Remember that if a user has execute only access
35 to F<PerlShr>, VMS will treat it as if it were a privileged shareable
36 image, and will therefore require all downstream shareable images to be
40 Finally, F<Perl.Exe> is an executable image containing the main
41 entry point for Perl, as well as some initialization code. It
42 should be placed in a public directory, and made world executable.
43 In order to run Perl with command line arguments, you should
44 define a foreign command to invoke this image.
46 =head2 Perl Extensions
48 Perl extensions are packages which provide both XS and Perl code
49 to add new functionality to perl. (XS is a meta-language which
50 simplifies writing C code which interacts with Perl, see
51 L<perlapi> for more details.) The Perl code for an
52 extension is treated like any other library module - it's
53 made available in your script through the appropriate
54 C<use> or C<require> statement, and usually defines a Perl
55 package containing the extension.
57 The portion of the extension provided by the XS code may be
58 connected to the rest of Perl in either of two ways. In the
59 B<static> configuration, the object code for the extension is
60 linked directly into F<PerlShr.Exe>, and is initialized whenever
61 Perl is invoked. In the B<dynamic> configuration, the extension's
62 machine code is placed into a separate shareable image, which is
63 mapped by Perl's DynaLoader when the extension is C<use>d or
64 C<require>d in your script. This allows you to maintain the
65 extension as a separate entity, at the cost of keeping track of the
66 additional shareable image. Most extensions can be set up as either
69 The source code for an extension usually resides in its own
70 directory. At least three files are generally provided:
71 I<Extshortname>F<.xs> (where I<Extshortname> is the portion of
72 the extension's name following the last C<::>), containing
73 the XS code, I<Extshortname>F<.pm>, the Perl library module
74 for the extension, and F<Makefile.PL>, a Perl script which uses
75 the C<MakeMaker> library modules supplied with Perl to generate
76 a F<Descrip.MMS> file for the extension.
78 =head3 Installing static extensions
80 Since static extensions are incorporated directly into
81 F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a
82 new extension. You should edit the main F<Descrip.MMS> or F<Makefile>
83 you use to build Perl, adding the extension's name to the C<ext>
84 macro, and the extension's object file to the C<extobj> macro.
85 You'll also need to build the extension's object file, either
86 by adding dependencies to the main F<Descrip.MMS>, or using a
87 separate F<Descrip.MMS> for the extension. Then, rebuild
88 F<PerlShr.Exe> to incorporate the new code.
90 Finally, you'll need to copy the extension's Perl library
91 module to the F<[.>I<Extname>F<]> subdirectory under one
92 of the directories in C<@INC>, where I<Extname> is the name
93 of the extension, with all C<::> replaced by C<.> (e.g.
94 the library module for extension Foo::Bar would be copied
95 to a F<[.Foo.Bar]> subdirectory).
97 =head3 Installic dynamic extensions
99 First, you'll need to compile the XS code into a shareable image,
100 either by hand or using the F<Descrip.MMS> supplied with the
101 extension. If you're building the shareable image by hand, please
102 note the following points:
103 - The shareable image must be linked to F<PerlShr.Exe>, so it
104 has access to Perl's global variables and routines. In
105 order to specify the correct attributes for psects in
106 F<PerlShr.Exe>, you should include the linker options file
107 F<PerlShr_Attr.Opt> in the Link command. (This file is
108 generated when F<PerlShr.Exe> is built, and is found in the
109 main Perl source directory.
110 - The entry point for the C<boot_>I<Extname> routine (where
111 I<Extname> is the name of the extension, with all C<::>
112 replaced by C<__>) must be a universal symbol. No other
113 universal symbols are required to use the shareable image
114 with Perl, though you may want to include additional
115 universal symbols if you plan to share code or data among
116 different extensions.
117 The shareable image can be placed in any of several locations:
118 - the F<[.Auto.>I<Extname>F<]> subdirectory of one of
119 the directories in C<@INC>, where I<Extname> is the
120 name of the extension, with each C<::> translated to C<.>
121 (e.g. for extension Foo::Bar, you would use the
122 F<[.Auto.Foo.Bar]> subdirectory), or
123 - one of the directories in C<@INC>, or
124 - a directory which the extensions Perl library module
125 passes to the DynaLoader when asking it to map
126 the shareable image, or
127 - F<Sys$Share> or F<Sys$Library>.
128 If the shareable image isn't in any of these places, you'll need
129 to define a logical name I<Extshortname>, where I<Extshortname>
130 is the portion of the extension's name after the last C<::>, which
131 translates to the full file specification of the shareable image.
133 Once you've got the shareable image set up, you should copy the
134 extension's Perl library module to the appropriate library directory
135 (see the section above on installing static extensions).
139 Directions for building and installing Perl 5 can be found in
140 the file F<ReadMe.VMS> in the main source directory of the
143 =head1 File specifications
145 We have tried to make Perl aware of both VMS-style and Unix-
146 style file specifications wherever possible. You may use
147 either style, or both, on the command line and in scripts,
148 but you may not combine the two styles within a single fle
149 specfication. Filenames are, of course, still case-
150 insensitive. For consistency, most Perl routines return
151 filespecs using lower case latters only, regardless of the
152 case used in the arguments passed to them. (This is true
153 only when running under VMS; Perl respects the case-
154 sensitivity of OSs like Unix.)
156 We've tried to minimize the dependence of Perl library
157 modules on Unix syntax, but you may find that some of these,
158 as well as some scripts written for Unix systems, will
159 require that you use Unix syntax, since they will assume that
160 '/' is the directory separator, etc. If you find instances
161 of this in the Perl distribution itself, please let us know,
162 so we can try to work around them.
164 =head1 Command line redirection
166 Perl for VMS supports redirection of input and output on the
167 command line, using a subset of Bourne shell syntax:
168 <F<file> reads stdin from F<file>,
169 >F<file> writes stdout to F<file>,
170 >>F<file> appends stdout to F<file>,
171 2>F<file> writes stderr to F<file>, and
172 2>>F<file> appends stderr to F<file>.
174 In addition, output may be piped to a subprocess, using the
175 character '|'. Anything after this character on the command
176 line is passed to a subprocess for execution; the subprocess
177 takes the output of Perl as its input.
179 Finally, if the command line ends with '&', the entire
180 command is run in the background as an asynchronous
185 Input and output pipes to Perl filehandles are supported; the
186 "file name" is passed to lib$spawn() for asynchronous
187 execution. You should be careful to close any pipes you have
188 opened in a Perl script, lest you leave any "orphaned"
189 subprocesses around when Perl exits.
191 You may also use backticks to invoke a DCL subprocess, whose
192 output is used as the return value of the expression. The
193 string between the backticks is passed directly to lib$spawn
194 as the command to execute. In this case, Perl will wait for
195 the subprocess to complete before continuing.
197 =head1 Wildcard expansion
199 File specifications containing wildcards are allowed both on
200 the command line and within Perl globs (e.g. <C<*.c>>). If
201 the wildcard filespec uses VMS syntax, the resultant
202 filespecs will follow VMS syntax; if a Unix-style filespec is
203 passed in, Unix-style filespecs will be returned..
205 If the wildcard filespec contains a device or directory
206 specification, then the resultant filespecs will also contain
207 a device and directory; otherwise, device and directory
208 information are removed. VMS-style resultant filespecs will
209 contain a full device and directory, while Unix-style
210 resultant filespecs will contain only as much of a directory
211 path as was present in the input filespec. For example, if
212 your default directory is Perl_Root:[000000], the expansion
213 of C<[.t]*.*> will yield filespecs like
214 "perl_root:[t]base.dir", while the expansion of C<t/*/*> will
215 yield filespecs like "t/base.dir". (This is done to match
216 the behavior of glob expansion performed by Unix shells.)
218 Similarly, the resultant filespec will the file version only
219 if one was present in the input filespec.
221 =head1 PERL5LIB and PERLLIB
223 The PERL5LIB and PERLLIB logical names work as
224 documented L<perl>, except that the element
225 separator is '|' instead of ':'. The directory
226 specifications may use either VMS or Unix syntax.
230 Reading the elements of the %ENV array returns the
231 translation of the logical name specified by the key,
232 according to the normal search order of access modes and
233 logical name tables. In addition, the keys C<home>,
234 C<path>,C<term>, and C<user> return the CRTL "environment
235 variables" of the same names. The key C<default> returns the
236 current default device and directory specification.
238 Setting an element of %ENV defines a supervisor-mode logical
239 name in the process logical name table. C<Undef>ing or
240 C<delete>ing an element of %ENV deletes the equivalent user-
241 mode or supervisor-mode logical name from the process logical
242 name table. If you use C<undef>, the %ENV element remains
243 empty. If you use C<delete>, another attempt is made at
244 logical name translation after the deletion, so an inner-mode
245 logical name or a name in another logical name table will
246 replace the logical name just deleted.
248 In all operations on %ENV, the key string is treated as if it
249 were entirely uppercase, regardless of the case actually
250 specified in the Perl expression.
252 =head1 Perl functions
254 As of the time this document was last revised, the following
255 Perl functions were implemented in the VMS port of Perl
256 (functions marked with * are discussed in more detail below):
258 file tests*, abs, alarm, atan, binmode*, bless,
259 caller, chdir, chmod, chown, chomp, chop, chr,
260 close, closedir, cos, defined, delete, die, do,
261 each, endpwent, eof, eval, exec*, exists, exit,
262 exp, fileno, fork*, getc, getpwent*, getpwnam*,
263 getpwuid*, glob, goto, grep, hex, import, index,
264 int, join, keys, kill, last, lc, lcfirst, length,
265 local, localtime, log, m//, map, mkdir, my, next,
266 no, oct, open, opendir, ord, pack, pipe, pop, pos,
267 print, printf, push, q//, qq//, qw//, qx//,
268 quotemeta, rand, read, readdir, redo, ref, rename,
269 require, reset, return, reverse, rewinddir, rindex,
270 rmdir, s///, scalar, seek, seekdir, select(internal)*,
271 setpwent, shift, sin, sleep, sort, splice, split,
272 sprintf, sqrt, srand, stat, study, substr, sysread,
273 system*, syswrite, tell, telldir, tie, time, times*,
274 tr///, uc, ucfirst, umask, undef, unlink*, unpack,
275 untie, unshift, use, utime*, values, vec, wait,
276 waitpid*, wantarray, warn, write, y///
278 The following functions were not implemented in the VMS port,
279 and calling them produces a fatal error (usually) or
280 undefined behavior (rarely, we hope):
282 chroot, crypt, dbmclose, dbmopen, dump, fcntl,
283 flock, getlogin, getpgrp, getppid, getpriority,
284 getgrent, kill, getgrgid, getgrnam, setgrent,
285 endgrent, gmtime, ioctl, link, lstst, msgctl,
286 msgget, msgsend, msgrcv, readlink,
287 select(system call), semctl, semget, semop,
288 setpgrp, setpriority, shmctl, shmget, shmread,
289 shmwrite, socketpair, symlink, syscall, truncate
291 The following functions may or may not be implemented,
292 depending on what type of socket support you've built into
294 accept, bind, connect, getpeername,
295 gethostbyname, getnetbyname, getprotobyname,
296 getservbyname, gethostbyaddr, getnetbyaddr,
297 getprotobynumber, getservbyport, gethostent,
298 getnetent, getprotoent, getservent, sethostent,
299 setnetent, setprotoent, setservent, endhostent,
300 endnetent, endprotoent, endservent, getsockname,
301 getsockopt, listen, recv, send, setsockopt,
307 The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>,
308 C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as
309 advertised. The return values for C<-r>, C<-w>, and C<-x>
310 tell you whether you can actually access the file; this may
311 not reflect the UIC-based file protections. Since real and
312 effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>,
313 and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>.
314 Similarly, several other tests, including C<-A>, C<-g>, C<-k>,
315 C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under
316 VMS, and the values returned by these tests reflect whatever
317 your CRTL C<stat()> routine does to the equivalent bits in the
318 st_mode field. Finally, C<-d> returns true if passed a device
319 specification without an explicit directory (e.g. C<DUA1:>), as
320 well as if passed a directory.
322 =item binmode FILEHANDLE
324 The C<binmode> operator has no effect under VMS. It will
325 return TRUE whenever called, but will not affect I/O
326 operations on the filehandle given as its argument.
330 The C<exec> operator behaves in one of two different ways.
331 If called after a call to C<fork>, it will invoke the CRTL
332 C<execv()> routine, passing its arguments to the subprocess
333 created by C<fork> for execution. In this case, it is
334 subject to all limitations that affect C<execv()>. (In
335 particular, this usually means that the command executed in
336 the subprocess must be an image compiled from C source code,
337 and that your options for passing file descriptors and signal
338 handlers to the subprocess are limited.)
340 If the call to C<exec> does not follow a call to C<fork>, it
341 will cause Perl to exit, and to invoke the command given as
342 an argument to C<exec> via C<lib$do_command>. If the argument
343 begins with a '$' (other than as part of a filespec), then it
344 is executed as a DCL command. Otherwise, the first token on
345 the command line is treated as the filespec of an image to
346 run, and an attempt is made to invoke it (using F<.Exe> and
347 the process defaults to expand the filespec) and pass the
348 rest of C<exec>'s argument to it as parameters.
350 You can use C<exec> in both ways within the same script, as
351 long as you call C<fork> and C<exec> in pairs. Perl
352 keeps track of how many times C<fork> and C<exec> have been
353 called, and will call the CRTL C<execv()> routine if there have
354 previously been more calls to C<fork> than to C<exec>.
358 The C<fork> operator works in the same way as the CRTL
359 C<vfork()> routine, which is quite different under VMS than
360 under Unix. Specifically, while C<fork> returns 0 after it
361 is called and the subprocess PID after C<exec> is called, in
362 both cases the thread of execution is within the parent
363 process, so there is no opportunity to perform operations in
364 the subprocess before calling C<exec>.
366 In general, the use of C<fork> and C<exec> to create
367 subprocess is not recommended under VMS; wherever possible,
368 use the C<system> operator or piped filehandles instead.
374 These operators obtain the information described in L<perlfunc>,
375 if you have the privileges necessary to retrieve the named user's
376 UAF information via C<sys$getuai>. If not, then only the C<$name>,
377 C<$uid>, and C<$gid> items are returned. The C<$dir> item contains
378 the login directory in VMS syntax, while the C<$comment> item
379 contains the login directory in Unix syntax. The C<$gcos> item
380 contains the owner field from the UAF record. The C<$quota>
385 Since VMS keeps track of files according to a different scheme
386 than Unix, it's not really possible to represent the file's ID
387 in the C<st_dev> and C<st_ino> fields of a C<struct stat>. Perl
388 tries its best, though, and the values it uses are pretty unlikely
389 to be the same for two different files. We can't guarantee this,
390 though, so caveat scriptor.
394 The C<system> operator creates a subprocess, and passes its
395 arguments to the subprocess for execution as a DCL command.
396 Since the subprocess is created directly via lib$spawn, any
397 valid DCL command string may be specified. If LIST consists
398 of the empty string, C<system> spawns an interactive DCL subprocess,
399 in the same fashion as typiing B<SPAWN> at the DCL prompt.
400 Perl waits for the subprocess to complete before continuing
401 execution in the current process.
405 The array returned by the C<times> operator is divided up
406 according to the same rules the CRTL C<times()> routine.
407 Therefore, the "system time" elements will always be 0, since
408 there is no difference between "user time" and "system" time
409 under VMS, and the time accumulated by subprocess may or may
410 not appear separately in the "child time" field, depending on
411 whether L<times> keeps track of subprocesses separately. Note
412 especially that the VAXCRTL (at least) keeps track only of
413 subprocesses spawned using L<fork> and L<exec>; it will not
414 accumulate the times of suprocesses spawned via pipes, L<system>,
419 C<unlink> will delete the highest version of a file only; in
420 order to delete all versions, you need to say
421 1 while (unlink LIST);
422 You may need to make this change to scripts written for a
423 Unix system which expect that after a call to C<unlink>,
424 no files with the names passed to C<unlink> will exist.
425 (Note: This can be changed at compile time; if you
426 C<use Config> and C<$Config{'d_unlink_all_versions'}> is
427 C<define>, then C<unlink> will delete all versions of a
428 file on the first call.)
430 C<unlink> will delete a file if at all possible, even if it
431 requires changing file protection (though it won't try to
432 change the protection of the parent directory). You can tell
433 whether you've got explicit delete access to a file by using the
434 C<VMS::Filespec::candelete> operator. For instance, in order
435 to delete only files to which you have delete access, you could
440 next unless VMS::Filespec::candelete($file);
441 $num += unlink $file;
445 Finally, if C<unlink> has to change the file protection to
446 delete the file, and you interrupt it in midstream, the file
447 may be left intact, but with a changed ACL allowing you delete
452 Since ODS-2, the VMS file structure for disk files, does not keep
453 track of access times, this operator changes only the modification
454 time of the file (VMS revision date).
456 =item waitpid PID,FLAGS
458 If PID is a subprocess started by a piped L<open>, C<waitpid>
459 will wait for that subprocess, and return its final
460 status value. If PID is a subprocess created in some other way
461 (e.g. SPAWNed before Perl was invoked), or is not a subprocess of
462 the current process, C<waitpid> will check once per second whether
463 the process has completed, and when it has, will return 0. (If PID
464 specifies a process that isn't a subprocess of the current process,
465 and you invoked Perl with the C<-w> switch, a warning will be issued.)
467 The FLAGS argument is ignored in all cases.
471 This document was last updated on 16-Dec-1994, for Perl 5,