3 perlvms - VMS-specific documentation for Perl
7 Gathered below are notes describing details of Perl 5's
8 behavior on VMS. They are a supplement to the regular Perl 5
9 documentation, so we have focussed on the ways in which Perl
10 5 functions differently under VMS than it does under Unix,
11 and on the interactions between Perl and the rest of the
12 operating system. We haven't tried to duplicate complete
13 descriptions of Perl features from the main Perl
14 documentation, which can be found in the F<[.pod]>
15 subdirectory of the Perl distribution.
17 We hope these notes will save you from confusion and lost
18 sleep when writing Perl scripts on VMS. If you find we've
19 missed something you think should appear here, please don't
20 hesitate to drop a line to vmsperl@genetics.upenn.edu.
22 =head1 Organization of Perl Images
26 During the installation process, three Perl images are produced.
27 F<Miniperl.Exe> is an executable image which contains all of
28 the basic functionality of Perl, but cannot take advantage of
29 Perl extensions. It is used to generate several files needed
30 to build the complete Perl and various extensions. Once you've
31 finished installing Perl, you can delete this image.
33 Most of the complete Perl resides in the shareable image
34 F<PerlShr.Exe>, which provides a core to which the Perl executable
35 image and all Perl extensions are linked. You should place this
36 image in F<Sys$Share>, or define the logical name F<PerlShr> to
37 translate to the full file specification of this image. It should
38 be world readable. (Remember that if a user has execute only access
39 to F<PerlShr>, VMS will treat it as if it were a privileged shareable
40 image, and will therefore require all downstream shareable images to be
44 Finally, F<Perl.Exe> is an executable image containing the main
45 entry point for Perl, as well as some initialization code. It
46 should be placed in a public directory, and made world executable.
47 In order to run Perl with command line arguments, you should
48 define a foreign command to invoke this image.
50 =head2 Perl Extensions
52 Perl extensions are packages which provide both XS and Perl code
53 to add new functionality to perl. (XS is a meta-language which
54 simplifies writing C code which interacts with Perl, see
55 L<perlapi> for more details.) The Perl code for an
56 extension is treated like any other library module - it's
57 made available in your script through the appropriate
58 C<use> or C<require> statement, and usually defines a Perl
59 package containing the extension.
61 The portion of the extension provided by the XS code may be
62 connected to the rest of Perl in either of two ways. In the
63 B<static> configuration, the object code for the extension is
64 linked directly into F<PerlShr.Exe>, and is initialized whenever
65 Perl is invoked. In the B<dynamic> configuration, the extension's
66 machine code is placed into a separate shareable image, which is
67 mapped by Perl's DynaLoader when the extension is C<use>d or
68 C<require>d in your script. This allows you to maintain the
69 extension as a separate entity, at the cost of keeping track of the
70 additional shareable image. Most extensions can be set up as either
73 The source code for an extension usually resides in its own
74 directory. At least three files are generally provided:
75 I<Extshortname>F<.xs> (where I<Extshortname> is the portion of
76 the extension's name following the last C<::>), containing
77 the XS code, I<Extshortname>F<.pm>, the Perl library module
78 for the extension, and F<Makefile.PL>, a Perl script which uses
79 the C<MakeMaker> library modules supplied with Perl to generate
80 a F<Descrip.MMS> file for the extension.
82 =head2 Installing static extensions
84 Since static extensions are incorporated directly into
85 F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a
86 new extension. You should edit the main F<Descrip.MMS> or F<Makefile>
87 you use to build Perl, adding the extension's name to the C<ext>
88 macro, and the extension's object file to the C<extobj> macro.
89 You'll also need to build the extension's object file, either
90 by adding dependencies to the main F<Descrip.MMS>, or using a
91 separate F<Descrip.MMS> for the extension. Then, rebuild
92 F<PerlShr.Exe> to incorporate the new code.
94 Finally, you'll need to copy the extension's Perl library
95 module to the F<[.>I<Extname>F<]> subdirectory under one
96 of the directories in C<@INC>, where I<Extname> is the name
97 of the extension, with all C<::> replaced by C<.> (e.g.
98 the library module for extension Foo::Bar would be copied
99 to a F<[.Foo.Bar]> subdirectory).
101 =head2 Installing dynamic extensions
103 In general, the distributed kit for a Perl extension includes
104 a file named Makefile.PL, which is a Perl program which is used
105 to create a F<Descrip.MMS> file which can be used to build and
106 install the files required by the extension. The kit should be
107 unpacked into a directory tree B<not> under the main Perl source
108 directory, and the procedure for building the extension is simply
110 $ perl Makefile.PL ! Create Descrip.MMS
111 $ mmk ! Build necessary files
112 $ mmk test ! Run test code, if supplied
113 $ mmk install ! Install into public Perl tree
115 I<N.B.> The procedure by which extensions are built and
116 tested creates several levels (at least 4) under the
117 directory in which the extension's source files live.
118 For this reason, you shouldn't nest the source directory
119 too deeply in your directory structure, lest you eccedd RMS'
120 maximum of 8 levels of subdirectory in a filespec. (You
121 can use rooted logical names to get another 8 levels of
122 nesting, if you can't place the files near the top of
123 the physical directory structure.)
125 VMS support for this process in the current release of Perl
126 is sufficient to handle most extensions. However, it does
127 not yet recognize extra libraries required to build shareable
128 images which are part of an extension, so these must be added
129 to the linker options file for the extension by hand. For
130 instance, if the F<PGPLOT> extension to Perl requires the
131 F<PGPLOTSHR.EXE> shareable image in order to properly link
132 the Perl extension, then the line C<PGPLOTSHR/Share> must
133 be added to the linker options file F<PGPLOT.Opt> produced
134 during the build process for the Perl extension.
136 By default, the shareable image for an extension is placed
137 in the F<[.Lib.Auto.I<Arch>.I<Extname>]> directory of the
138 installed Perl directory tree (where I<Arch> is F<VMS_VAX> or
139 F<VMS_AXP>, and I<Extname> is the name of the extension, with
140 each C<::> translated to C<.>). However, it can be manually
141 placed in any of several locations:
142 - the F<[.Lib.Auto.I<Extname>]> subdirectory of one of
143 the directories in C<@INC>, or
144 - one of the directories in C<@INC>, or
145 - a directory which the extensions Perl library module
146 passes to the DynaLoader when asking it to map
147 the shareable image, or
148 - F<Sys$Share> or F<Sys$Library>.
149 If the shareable image isn't in any of these places, you'll need
150 to define a logical name I<Extshortname>, where I<Extshortname>
151 is the portion of the extension's name after the last C<::>, which
152 translates to the full file specification of the shareable image.
156 Directions for building and installing Perl 5 can be found in
157 the file F<ReadMe.VMS> in the main source directory of the
160 =head1 File specifications
162 We have tried to make Perl aware of both VMS-style and Unix-
163 style file specifications wherever possible. You may use
164 either style, or both, on the command line and in scripts,
165 but you may not combine the two styles within a single fle
166 specfication. Filenames are, of course, still case-
167 insensitive. For consistency, most Perl routines return
168 filespecs using lower case latters only, regardless of the
169 case used in the arguments passed to them. (This is true
170 only when running under VMS; Perl respects the case-
171 sensitivity of OSs like Unix.)
173 We've tried to minimize the dependence of Perl library
174 modules on Unix syntax, but you may find that some of these,
175 as well as some scripts written for Unix systems, will
176 require that you use Unix syntax, since they will assume that
177 '/' is the directory separator, etc. If you find instances
178 of this in the Perl distribution itself, please let us know,
179 so we can try to work around them.
181 =head1 Command line redirection
183 Perl for VMS supports redirection of input and output on the
184 command line, using a subset of Bourne shell syntax:
185 <F<file> reads stdin from F<file>,
186 >F<file> writes stdout to F<file>,
187 >>F<file> appends stdout to F<file>,
188 2>F<file> writes stderr to F<file>, and
189 2>>F<file> appends stderr to F<file>.
191 In addition, output may be piped to a subprocess, using the
192 character '|'. Anything after this character on the command
193 line is passed to a subprocess for execution; the subprocess
194 takes the output of Perl as its input.
196 Finally, if the command line ends with '&', the entire
197 command is run in the background as an asynchronous
202 Input and output pipes to Perl filehandles are supported; the
203 "file name" is passed to lib$spawn() for asynchronous
204 execution. You should be careful to close any pipes you have
205 opened in a Perl script, lest you leave any "orphaned"
206 subprocesses around when Perl exits.
208 You may also use backticks to invoke a DCL subprocess, whose
209 output is used as the return value of the expression. The
210 string between the backticks is passed directly to lib$spawn
211 as the command to execute. In this case, Perl will wait for
212 the subprocess to complete before continuing.
214 =head1 Wildcard expansion
216 File specifications containing wildcards are allowed both on
217 the command line and within Perl globs (e.g. <C<*.c>>). If
218 the wildcard filespec uses VMS syntax, the resultant
219 filespecs will follow VMS syntax; if a Unix-style filespec is
220 passed in, Unix-style filespecs will be returned..
222 If the wildcard filespec contains a device or directory
223 specification, then the resultant filespecs will also contain
224 a device and directory; otherwise, device and directory
225 information are removed. VMS-style resultant filespecs will
226 contain a full device and directory, while Unix-style
227 resultant filespecs will contain only as much of a directory
228 path as was present in the input filespec. For example, if
229 your default directory is Perl_Root:[000000], the expansion
230 of C<[.t]*.*> will yield filespecs like
231 "perl_root:[t]base.dir", while the expansion of C<t/*/*> will
232 yield filespecs like "t/base.dir". (This is done to match
233 the behavior of glob expansion performed by Unix shells.)
235 Similarly, the resultant filespec will the file version only
236 if one was present in the input filespec.
238 =head1 PERL5LIB and PERLLIB
240 The PERL5LIB and PERLLIB logical names work as
241 documented L<perl>, except that the element
242 separator is '|' instead of ':'. The directory
243 specifications may use either VMS or Unix syntax.
245 =head1 Perl functions
247 As of the time this document was last revised, the following
248 Perl functions were implemented in the VMS port of Perl
249 (functions marked with * are discussed in more detail below):
251 file tests*, abs, alarm, atan, binmode*, bless,
252 caller, chdir, chmod, chown, chomp, chop, chr,
253 close, closedir, cos, crypt*, defined, delete,
254 die, do, each, endpwent, eof, eval, exec*, exists,
255 exit, exp, fileno, fork*, getc, getlogin, getpwent*,
256 getpwnam*, getpwuid*, glob, gmtime*, goto, grep, hex,
257 import, index, int, join, keys, kill*, last, lc,
258 lcfirst, length, local, localtime, log, m//, map,
259 mkdir, my, next, no, oct, open, opendir, ord, pack,
260 pipe, pop, pos, print, printf, push, q//, qq//, qw//,
261 qx//, quotemeta, rand, read, readdir, redo, ref, rename,
262 require, reset, return, reverse, rewinddir, rindex,
263 rmdir, s///, scalar, seek, seekdir, select(internal),
264 select (system call)*, setpwent, shift, sin, sleep,
265 sort, splice, split, sprintf, sqrt, srand, stat,
266 study, substr, sysread, system*, syswrite, tell,
267 telldir, tie, time, times*, tr///, uc, ucfirst, umask,
268 undef, unlink*, unpack, untie, unshift, use, utime*,
269 values, vec, wait, waitpid*, wantarray, warn, write, y///
271 The following functions were not implemented in the VMS port,
272 and calling them produces a fatal error (usually) or
273 undefined behavior (rarely, we hope):
275 chroot, dbmclose, dbmopen, dump, fcntl, flock,
276 getpgrp, getppid, getpriority, getgrent, getgrgid,
277 getgrnam, setgrent, endgrent, ioctl, link, lstat,
278 msgctl, msgget, msgsend, msgrcv, readlink, semctl,
279 semget, semop, setpgrp, setpriority, shmctl, shmget,
280 shmread, shmwrite, socketpair, symlink, syscall, truncate
282 The following functions may or may not be implemented,
283 depending on what type of socket support you've built into
285 accept, bind, connect, getpeername,
286 gethostbyname, getnetbyname, getprotobyname,
287 getservbyname, gethostbyaddr, getnetbyaddr,
288 getprotobynumber, getservbyport, gethostent,
289 getnetent, getprotoent, getservent, sethostent,
290 setnetent, setprotoent, setservent, endhostent,
291 endnetent, endprotoent, endservent, getsockname,
292 getsockopt, listen, recv, select(system call)*,
293 send, setsockopt, shutdown, socket
298 The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>,
299 C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as
300 advertised. The return values for C<-r>, C<-w>, and C<-x>
301 tell you whether you can actually access the file; this may
302 not reflect the UIC-based file protections. Since real and
303 effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>,
304 and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>.
305 Similarly, several other tests, including C<-A>, C<-g>, C<-k>,
306 C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under
307 VMS, and the values returned by these tests reflect whatever
308 your CRTL C<stat()> routine does to the equivalent bits in the
309 st_mode field. Finally, C<-d> returns true if passed a device
310 specification without an explicit directory (e.g. C<DUA1:>), as
311 well as if passed a directory.
313 =item binmode FILEHANDLE
315 The C<binmode> operator has no effect under VMS. It will
316 return TRUE whenever called, but will not affect I/O
317 operations on the filehandle given as its argument.
319 =item crypt PLAINTEXT, USER
321 The C<crypt> operator uses the C<sys$hash_password> system
322 service to generate the hashed representation of PLAINTEXT.
323 If USER is a valid username, the algorithm and salt values
324 are taken from that user's UAF record. If it is not, then
325 the preferred algorithm and a salt of 0 are used. The
326 quadword encrypted value is returned as an 8-character string.
328 The value returned by C<crypt> may be compared against
329 the encrypted password from the UAF returned by the C<getpw*>
330 functions, in order to authenticate users. If you're
331 going to do this, remember that the encrypted password in
332 the UAF was generated using uppercase username and
333 password strings; you'll have to upcase the arguments to
334 C<crypt> to insure that you'll get the proper value:
336 sub validate_passwd {
337 my($user,$passwd) = @_;
339 if ( !($pwdhash = (getpwnam($user))[1]) ||
340 $pwdhash ne crypt("\U$passwd","\U$name") ) {
341 intruder_alert($name);
348 The C<exec> operator behaves in one of two different ways.
349 If called after a call to C<fork>, it will invoke the CRTL
350 C<execv()> routine, passing its arguments to the subprocess
351 created by C<fork> for execution. In this case, it is
352 subject to all limitations that affect C<execv()>. (In
353 particular, this usually means that the command executed in
354 the subprocess must be an image compiled from C source code,
355 and that your options for passing file descriptors and signal
356 handlers to the subprocess are limited.)
358 If the call to C<exec> does not follow a call to C<fork>, it
359 will cause Perl to exit, and to invoke the command given as
360 an argument to C<exec> via C<lib$do_command>. If the argument
361 begins with a '$' (other than as part of a filespec), then it
362 is executed as a DCL command. Otherwise, the first token on
363 the command line is treated as the filespec of an image to
364 run, and an attempt is made to invoke it (using F<.Exe> and
365 the process defaults to expand the filespec) and pass the
366 rest of C<exec>'s argument to it as parameters.
368 You can use C<exec> in both ways within the same script, as
369 long as you call C<fork> and C<exec> in pairs. Perl
370 keeps track of how many times C<fork> and C<exec> have been
371 called, and will call the CRTL C<execv()> routine if there have
372 previously been more calls to C<fork> than to C<exec>.
376 The C<fork> operator works in the same way as the CRTL
377 C<vfork()> routine, which is quite different under VMS than
378 under Unix. Specifically, while C<fork> returns 0 after it
379 is called and the subprocess PID after C<exec> is called, in
380 both cases the thread of execution is within the parent
381 process, so there is no opportunity to perform operations in
382 the subprocess before calling C<exec>.
384 In general, the use of C<fork> and C<exec> to create
385 subprocess is not recommended under VMS; wherever possible,
386 use the C<system> operator or piped filehandles instead.
394 These operators obtain the information described in L<perlfunc>,
395 if you have the privileges necessary to retrieve the named user's
396 UAF information via C<sys$getuai>. If not, then only the C<$name>,
397 C<$uid>, and C<$gid> items are returned. The C<$dir> item contains
398 the login directory in VMS syntax, while the C<$comment> item
399 contains the login directory in Unix syntax. The C<$gcos> item
400 contains the owner field from the UAF record. The C<$quota>
405 The C<gmtime> operator will function properly if you have a
406 working CRTL C<gmtime()> routine, or if the logical name
407 SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds
408 which must be added to UTC to yield local time. (This logical
409 name is defined automatically if you are running a version of
410 VMS with built-in UTC support.) If neither of these cases is
411 true, a warning message is printed, and C<undef> is returned.
415 In most cases, C<kill> kill is implemented via the CRTL's C<kill()>
416 function, so it will behave according to that function's
417 documentation. If you send a SIGKILL, however, the $DELPRC system
418 service is is called directly. This insures that the target
419 process is actually deleted, if at all possible. (The CRTL's C<kill()>
420 function is presently implemented via $FORCEX, which is ignored by
421 supervisor-mode images like DCL.)
423 Also, negative signal values don't do anything special under
424 VMS; they're just converted to the corresponding positive value.
426 =item select (system call)
428 If Perl was not built with socket support, the system call
429 version of C<select> is not available at all. If socket
430 support is present, then the system call version of
431 C<select> functions only for file descriptors attached
432 to sockets. It will not provide information about regular
433 files or pipes, since the CRTL C<select()> routine does not
434 provide this functionality.
438 Since VMS keeps track of files according to a different scheme
439 than Unix, it's not really possible to represent the file's ID
440 in the C<st_dev> and C<st_ino> fields of a C<struct stat>. Perl
441 tries its best, though, and the values it uses are pretty unlikely
442 to be the same for two different files. We can't guarantee this,
443 though, so caveat scriptor.
447 The C<system> operator creates a subprocess, and passes its
448 arguments to the subprocess for execution as a DCL command.
449 Since the subprocess is created directly via C<lib$spawn()>, any
450 valid DCL command string may be specified. If LIST consists
451 of the empty string, C<system> spawns an interactive DCL subprocess,
452 in the same fashion as typiing B<SPAWN> at the DCL prompt.
453 Perl waits for the subprocess to complete before continuing
454 execution in the current process.
458 The array returned by the C<times> operator is divided up
459 according to the same rules the CRTL C<times()> routine.
460 Therefore, the "system time" elements will always be 0, since
461 there is no difference between "user time" and "system" time
462 under VMS, and the time accumulated by subprocess may or may
463 not appear separately in the "child time" field, depending on
464 whether L<times> keeps track of subprocesses separately. Note
465 especially that the VAXCRTL (at least) keeps track only of
466 subprocesses spawned using L<fork> and L<exec>; it will not
467 accumulate the times of suprocesses spawned via pipes, L<system>,
472 C<unlink> will delete the highest version of a file only; in
473 order to delete all versions, you need to say
474 1 while (unlink LIST);
475 You may need to make this change to scripts written for a
476 Unix system which expect that after a call to C<unlink>,
477 no files with the names passed to C<unlink> will exist.
478 (Note: This can be changed at compile time; if you
479 C<use Config> and C<$Config{'d_unlink_all_versions'}> is
480 C<define>, then C<unlink> will delete all versions of a
481 file on the first call.)
483 C<unlink> will delete a file if at all possible, even if it
484 requires changing file protection (though it won't try to
485 change the protection of the parent directory). You can tell
486 whether you've got explicit delete access to a file by using the
487 C<VMS::Filespec::candelete> operator. For instance, in order
488 to delete only files to which you have delete access, you could
493 next unless VMS::Filespec::candelete($file);
494 $num += unlink $file;
498 Finally, if C<unlink> has to change the file protection to
499 delete the file, and you interrupt it in midstream, the file
500 may be left intact, but with a changed ACL allowing you delete
505 Since ODS-2, the VMS file structure for disk files, does not keep
506 track of access times, this operator changes only the modification
507 time of the file (VMS revision date).
509 =item waitpid PID,FLAGS
511 If PID is a subprocess started by a piped L<open>, C<waitpid>
512 will wait for that subprocess, and return its final
513 status value. If PID is a subprocess created in some other way
514 (e.g. SPAWNed before Perl was invoked), or is not a subprocess of
515 the current process, C<waitpid> will check once per second whether
516 the process has completed, and when it has, will return 0. (If PID
517 specifies a process that isn't a subprocess of the current process,
518 and you invoked Perl with the C<-w> switch, a warning will be issued.)
520 The FLAGS argument is ignored in all cases.
522 =head1 Perl variables
526 Reading the elements of the %ENV array returns the
527 translation of the logical name specified by the key,
528 according to the normal search order of access modes and
529 logical name tables. If you append a semicolon to the
530 logical name, followed by an integer, that integer is
531 used as the translation index for the logical name,
532 so that you can look up successive values for search
533 list logical names. For instance, if you say
535 $ Define STORY once,upon,a,time,there,was
536 $ perl -e "for ($i = 0; $i <= 6; $i++) " -
537 _$ -e "{ print $ENV{'foo'.$i},' '}"
539 Perl will print C<ONCE UPON A TIME THERE WAS>.
541 The %ENV keys C<home>, C<path>,C<term>, and C<user>
542 return the CRTL "environment variables" of the same
543 names, if these logical names are not defined. The
544 key C<default> returns the current default device
545 and directory specification, regardless of whether
546 there is a logical name DEFAULT defined..
548 Setting an element of %ENV defines a supervisor-mode logical
549 name in the process logical name table. C<Undef>ing or
550 C<delete>ing an element of %ENV deletes the equivalent user-
551 mode or supervisor-mode logical name from the process logical
552 name table. If you use C<undef>, the %ENV element remains
553 empty. If you use C<delete>, another attempt is made at
554 logical name translation after the deletion, so an inner-mode
555 logical name or a name in another logical name table will
556 replace the logical name just deleted. It is not possible
557 at present to define a search list logical name via %ENV.
559 In all operations on %ENV, the key string is treated as if it
560 were entirely uppercase, regardless of the case actually
561 specified in the Perl expression.
565 Since VMS status values are 32 bits wide, the value of C<$?>
566 is simply the final status value of the last subprocess to
567 complete. This differs from the behavior of C<$?> under Unix,
568 and under VMS' POSIX environment, in that the low-order 8 bits
569 of C<$?> do not specify whether the process terminated normally
570 or due to a signal, and you do not need to shift C<$?> 8 bits
571 to the right in order to find the process' exit status.
575 The string value of C<$!> is that returned by the CRTL's
576 strerror() function, so it will include the VMS message for
577 VMS-specific errors. The numeric value of C<$!> is the
578 value of C<errno>, except if errno is EVMSERR, in which
579 case C<$!> contains the value of vaxc$errno. Setting C<$!>
580 always sets errno to the value specified, and sets vaxc$errno
581 to 4 (NONAME-F-NOMSG).
585 This document was last updated on 16-Dec-1994, for Perl 5,
590 Charles Bailey bailey@genetics.upenn.edu