Commit | Line | Data |
e518068a |
1 | =head1 NAME |
2 | |
3 | perlvms - VMS-specific documentation for Perl |
4 | |
5 | =head1 DESCRIPTION |
a0d0e21e |
6 | |
748a9306 |
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 |
a0d0e21e |
12 | operating system. We haven't tried to duplicate complete |
748a9306 |
13 | descriptions of Perl features from the main Perl |
a0d0e21e |
14 | documentation, which can be found in the F<[.pod]> |
748a9306 |
15 | subdirectory of the Perl distribution. |
a0d0e21e |
16 | |
17 | We hope these notes will save you from confusion and lost |
748a9306 |
18 | sleep when writing Perl scripts on VMS. If you find we've |
a0d0e21e |
19 | missed something you think should appear here, please don't |
9bc98430 |
20 | hesitate to drop a line to vmsperl@perl.org. |
a0d0e21e |
21 | |
4e592037 |
22 | =head1 Installation |
23 | |
24 | Directions for building and installing Perl 5 can be found in |
25 | the file F<README.vms> in the main source directory of the |
26 | Perl distribution.. |
27 | |
e518068a |
28 | =head1 Organization of Perl Images |
748a9306 |
29 | |
e518068a |
30 | =head2 Core Images |
748a9306 |
31 | |
32 | During the installation process, three Perl images are produced. |
33 | F<Miniperl.Exe> is an executable image which contains all of |
34 | the basic functionality of Perl, but cannot take advantage of |
35 | Perl extensions. It is used to generate several files needed |
36 | to build the complete Perl and various extensions. Once you've |
37 | finished installing Perl, you can delete this image. |
38 | |
39 | Most of the complete Perl resides in the shareable image |
40 | F<PerlShr.Exe>, which provides a core to which the Perl executable |
41 | image and all Perl extensions are linked. You should place this |
42 | image in F<Sys$Share>, or define the logical name F<PerlShr> to |
43 | translate to the full file specification of this image. It should |
44 | be world readable. (Remember that if a user has execute only access |
45 | to F<PerlShr>, VMS will treat it as if it were a privileged shareable |
46 | image, and will therefore require all downstream shareable images to be |
47 | INSTALLed, etc.) |
48 | |
49 | |
50 | Finally, F<Perl.Exe> is an executable image containing the main |
51 | entry point for Perl, as well as some initialization code. It |
52 | should be placed in a public directory, and made world executable. |
53 | In order to run Perl with command line arguments, you should |
54 | define a foreign command to invoke this image. |
55 | |
56 | =head2 Perl Extensions |
57 | |
58 | Perl extensions are packages which provide both XS and Perl code |
59 | to add new functionality to perl. (XS is a meta-language which |
60 | simplifies writing C code which interacts with Perl, see |
2ceaccd7 |
61 | L<perlxs> for more details.) The Perl code for an |
748a9306 |
62 | extension is treated like any other library module - it's |
63 | made available in your script through the appropriate |
64 | C<use> or C<require> statement, and usually defines a Perl |
65 | package containing the extension. |
66 | |
67 | The portion of the extension provided by the XS code may be |
68 | connected to the rest of Perl in either of two ways. In the |
69 | B<static> configuration, the object code for the extension is |
70 | linked directly into F<PerlShr.Exe>, and is initialized whenever |
71 | Perl is invoked. In the B<dynamic> configuration, the extension's |
72 | machine code is placed into a separate shareable image, which is |
73 | mapped by Perl's DynaLoader when the extension is C<use>d or |
74 | C<require>d in your script. This allows you to maintain the |
75 | extension as a separate entity, at the cost of keeping track of the |
76 | additional shareable image. Most extensions can be set up as either |
77 | static or dynamic. |
78 | |
79 | The source code for an extension usually resides in its own |
80 | directory. At least three files are generally provided: |
81 | I<Extshortname>F<.xs> (where I<Extshortname> is the portion of |
82 | the extension's name following the last C<::>), containing |
83 | the XS code, I<Extshortname>F<.pm>, the Perl library module |
84 | for the extension, and F<Makefile.PL>, a Perl script which uses |
85 | the C<MakeMaker> library modules supplied with Perl to generate |
86 | a F<Descrip.MMS> file for the extension. |
87 | |
e518068a |
88 | =head2 Installing static extensions |
748a9306 |
89 | |
90 | Since static extensions are incorporated directly into |
91 | F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a |
92 | new extension. You should edit the main F<Descrip.MMS> or F<Makefile> |
93 | you use to build Perl, adding the extension's name to the C<ext> |
94 | macro, and the extension's object file to the C<extobj> macro. |
95 | You'll also need to build the extension's object file, either |
96 | by adding dependencies to the main F<Descrip.MMS>, or using a |
97 | separate F<Descrip.MMS> for the extension. Then, rebuild |
98 | F<PerlShr.Exe> to incorporate the new code. |
99 | |
100 | Finally, you'll need to copy the extension's Perl library |
101 | module to the F<[.>I<Extname>F<]> subdirectory under one |
102 | of the directories in C<@INC>, where I<Extname> is the name |
103 | of the extension, with all C<::> replaced by C<.> (e.g. |
104 | the library module for extension Foo::Bar would be copied |
105 | to a F<[.Foo.Bar]> subdirectory). |
106 | |
e518068a |
107 | =head2 Installing dynamic extensions |
108 | |
109 | In general, the distributed kit for a Perl extension includes |
110 | a file named Makefile.PL, which is a Perl program which is used |
111 | to create a F<Descrip.MMS> file which can be used to build and |
112 | install the files required by the extension. The kit should be |
c07a80fd |
113 | unpacked into a directory tree B<not> under the main Perl source |
e518068a |
114 | directory, and the procedure for building the extension is simply |
115 | |
e518068a |
116 | $ perl Makefile.PL ! Create Descrip.MMS |
117 | $ mmk ! Build necessary files |
118 | $ mmk test ! Run test code, if supplied |
119 | $ mmk install ! Install into public Perl tree |
120 | |
c07a80fd |
121 | I<N.B.> The procedure by which extensions are built and |
122 | tested creates several levels (at least 4) under the |
123 | directory in which the extension's source files live. |
124 | For this reason, you shouldn't nest the source directory |
39aca757 |
125 | too deeply in your directory structure, lest you exceed RMS' |
c07a80fd |
126 | maximum of 8 levels of subdirectory in a filespec. (You |
127 | can use rooted logical names to get another 8 levels of |
128 | nesting, if you can't place the files near the top of |
129 | the physical directory structure.) |
e518068a |
130 | |
131 | VMS support for this process in the current release of Perl |
132 | is sufficient to handle most extensions. However, it does |
133 | not yet recognize extra libraries required to build shareable |
134 | images which are part of an extension, so these must be added |
135 | to the linker options file for the extension by hand. For |
136 | instance, if the F<PGPLOT> extension to Perl requires the |
137 | F<PGPLOTSHR.EXE> shareable image in order to properly link |
138 | the Perl extension, then the line C<PGPLOTSHR/Share> must |
139 | be added to the linker options file F<PGPLOT.Opt> produced |
140 | during the build process for the Perl extension. |
141 | |
142 | By default, the shareable image for an extension is placed |
bbce6d69 |
143 | F<[.lib.site_perl.auto>I<Arch>.I<Extname>F<]> directory of the |
e518068a |
144 | installed Perl directory tree (where I<Arch> is F<VMS_VAX> or |
bbce6d69 |
145 | F<VMS_AXP>, and I<Extname> is the name of the extension, with |
146 | each C<::> translated to C<.>). (See the MakeMaker documentation |
147 | for more details on installation options for extensions.) |
4e592037 |
148 | However, it can be manually placed in any of several locations: |
bbce6d69 |
149 | - the F<[.Lib.Auto.>I<Arch>I<$PVers>I<Extname>F<]> subdirectory |
150 | of one of the directories in C<@INC> (where I<PVers> |
151 | is the version of Perl you're using, as supplied in C<$]>, |
152 | with '.' converted to '_'), or |
748a9306 |
153 | - one of the directories in C<@INC>, or |
154 | - a directory which the extensions Perl library module |
155 | passes to the DynaLoader when asking it to map |
156 | the shareable image, or |
157 | - F<Sys$Share> or F<Sys$Library>. |
158 | If the shareable image isn't in any of these places, you'll need |
159 | to define a logical name I<Extshortname>, where I<Extshortname> |
160 | is the portion of the extension's name after the last C<::>, which |
161 | translates to the full file specification of the shareable image. |
162 | |
4e592037 |
163 | =head1 File specifications |
748a9306 |
164 | |
4e592037 |
165 | =head2 Syntax |
a0d0e21e |
166 | |
748a9306 |
167 | We have tried to make Perl aware of both VMS-style and Unix- |
a0d0e21e |
168 | style file specifications wherever possible. You may use |
169 | either style, or both, on the command line and in scripts, |
39aca757 |
170 | but you may not combine the two styles within a single file |
1c9f8daa |
171 | specification. VMS Perl interprets Unix pathnames in much |
172 | the same way as the CRTL (I<e.g.> the first component of |
173 | an absolute path is read as the device name for the |
174 | VMS file specification). There are a set of functions |
175 | provided in the C<VMS::Filespec> package for explicit |
176 | interconversion between VMS and Unix syntax; its |
177 | documentation provides more details. |
178 | |
179 | Filenames are, of course, still case-insensitive. For |
180 | consistency, most Perl routines return filespecs using |
181 | lower case letters only, regardless of the case used in |
182 | the arguments passed to them. (This is true only when |
183 | running under VMS; Perl respects the case-sensitivity |
184 | of OSs like Unix.) |
a0d0e21e |
185 | |
748a9306 |
186 | We've tried to minimize the dependence of Perl library |
a0d0e21e |
187 | modules on Unix syntax, but you may find that some of these, |
188 | as well as some scripts written for Unix systems, will |
189 | require that you use Unix syntax, since they will assume that |
4e592037 |
190 | '/' is the directory separator, I<etc.> If you find instances |
748a9306 |
191 | of this in the Perl distribution itself, please let us know, |
a0d0e21e |
192 | so we can try to work around them. |
193 | |
4e592037 |
194 | =head2 Wildcard expansion |
195 | |
196 | File specifications containing wildcards are allowed both on |
07698885 |
197 | the command line and within Perl globs (e.g. C<E<lt>*.cE<gt>>). If |
4e592037 |
198 | the wildcard filespec uses VMS syntax, the resultant |
199 | filespecs will follow VMS syntax; if a Unix-style filespec is |
200 | passed in, Unix-style filespecs will be returned. |
201 | |
aa779de1 |
202 | In both cases, VMS wildcard expansion is performed. (csh-style |
203 | wildcard expansion is available if you use C<File::Glob::glob>.) |
4e592037 |
204 | If the wildcard filespec contains a device or directory |
205 | specification, then the resultant filespecs will also contain |
206 | a device and directory; otherwise, device and directory |
207 | information are removed. VMS-style resultant filespecs will |
208 | contain a full device and directory, while Unix-style |
209 | resultant filespecs will contain only as much of a directory |
210 | path as was present in the input filespec. For example, if |
211 | your default directory is Perl_Root:[000000], the expansion |
212 | of C<[.t]*.*> will yield filespecs like |
213 | "perl_root:[t]base.dir", while the expansion of C<t/*/*> will |
214 | yield filespecs like "t/base.dir". (This is done to match |
215 | the behavior of glob expansion performed by Unix shells.) |
216 | |
217 | Similarly, the resultant filespec will contain the file version |
218 | only if one was present in the input filespec. |
219 | |
220 | =head2 Pipes |
221 | |
222 | Input and output pipes to Perl filehandles are supported; the |
223 | "file name" is passed to lib$spawn() for asynchronous |
224 | execution. You should be careful to close any pipes you have |
225 | opened in a Perl script, lest you leave any "orphaned" |
226 | subprocesses around when Perl exits. |
227 | |
228 | You may also use backticks to invoke a DCL subprocess, whose |
229 | output is used as the return value of the expression. The |
aa779de1 |
230 | string between the backticks is handled as if it were the |
231 | argument to the C<system> operator (see below). In this case, |
232 | Perl will wait for the subprocess to complete before continuing. |
4e592037 |
233 | |
376ae1f1 |
234 | The mailbox (MBX) that perl can create to communicate with a pipe |
235 | defaults to a buffer size of 512. The default buffer size is |
1506e54c |
236 | adjustable via the logical name PERL_MBX_SIZE provided that the |
376ae1f1 |
237 | value falls between 128 and the SYSGEN parameter MAXBUF inclusive. |
238 | For example, to double the MBX size from the default within |
1506e54c |
239 | a Perl program, use C<$ENV{'PERL_MBX_SIZE'} = 1024;> and then |
376ae1f1 |
240 | open and use pipe constructs. An alternative would be to issue |
241 | the command: |
242 | |
243 | $ Define PERL_MBX_SIZE 1024 |
244 | |
245 | before running your wide record pipe program. A larger value may |
246 | improve performance at the expense of the BYTLM UAF quota. |
247 | |
4e592037 |
248 | =head1 PERL5LIB and PERLLIB |
249 | |
39aca757 |
250 | The PERL5LIB and PERLLIB logical names work as documented in L<perl>, |
4e592037 |
251 | except that the element separator is '|' instead of ':'. The |
252 | directory specifications may use either VMS or Unix syntax. |
253 | |
254 | =head1 Command line |
255 | |
256 | =head2 I/O redirection and backgrounding |
a0d0e21e |
257 | |
258 | Perl for VMS supports redirection of input and output on the |
259 | command line, using a subset of Bourne shell syntax: |
55497cff |
260 | |
07698885 |
261 | =over |
262 | |
263 | =item * |
264 | |
265 | C<E<lt>file> reads stdin from C<file>, |
266 | |
267 | =item * |
268 | |
269 | C<E<gt>file> writes stdout to C<file>, |
270 | |
271 | =item * |
272 | |
273 | C<E<gt>E<gt>file> appends stdout to C<file>, |
274 | |
275 | =item * |
276 | |
277 | C<2E<gt>file> writes stderr to C<file>, and |
278 | |
279 | =item * |
280 | |
281 | C<2E<gt>E<gt>file> appends stderr to C<file>. |
282 | |
283 | =back |
a0d0e21e |
284 | |
285 | In addition, output may be piped to a subprocess, using the |
286 | character '|'. Anything after this character on the command |
287 | line is passed to a subprocess for execution; the subprocess |
748a9306 |
288 | takes the output of Perl as its input. |
a0d0e21e |
289 | |
290 | Finally, if the command line ends with '&', the entire |
291 | command is run in the background as an asynchronous |
292 | subprocess. |
293 | |
4e592037 |
294 | =head2 Command line switches |
a0d0e21e |
295 | |
4e592037 |
296 | The following command line switches behave differently under |
297 | VMS than described in L<perlrun>. Note also that in order |
298 | to pass uppercase switches to Perl, you need to enclose |
299 | them in double-quotes on the command line, since the CRTL |
300 | downcases all unquoted strings. |
a0d0e21e |
301 | |
55497cff |
302 | =over 4 |
303 | |
edc7bc49 |
304 | =item -i |
305 | |
306 | If the C<-i> switch is present but no extension for a backup |
307 | copy is given, then inplace editing creates a new version of |
308 | a file; the existing copy is not deleted. (Note that if |
309 | an extension is given, an existing file is renamed to the backup |
310 | file, as is the case under other operating systems, so it does |
311 | not remain as a previous version under the original filename.) |
312 | |
4e592037 |
313 | =item -S |
a0d0e21e |
314 | |
376ae1f1 |
315 | If the C<"-S"> or C<-"S"> switch is present I<and> the script |
316 | name does not contain a directory, then Perl translates the |
317 | logical name DCL$PATH as a searchlist, using each translation |
318 | as a directory in which to look for the script. In addition, |
4e592037 |
319 | if no file type is specified, Perl looks in each directory |
320 | for a file matching the name specified, with a blank type, |
321 | a type of F<.pl>, and a type of F<.com>, in that order. |
a0d0e21e |
322 | |
4e592037 |
323 | =item -u |
748a9306 |
324 | |
4e592037 |
325 | The C<-u> switch causes the VMS debugger to be invoked |
326 | after the Perl program is compiled, but before it has |
327 | run. It does not create a core dump file. |
748a9306 |
328 | |
55497cff |
329 | =back |
330 | |
748a9306 |
331 | =head1 Perl functions |
a0d0e21e |
332 | |
333 | As of the time this document was last revised, the following |
748a9306 |
334 | Perl functions were implemented in the VMS port of Perl |
a0d0e21e |
335 | (functions marked with * are discussed in more detail below): |
336 | |
4fdae800 |
337 | file tests*, abs, alarm, atan, backticks*, binmode*, bless, |
a0d0e21e |
338 | caller, chdir, chmod, chown, chomp, chop, chr, |
c07a80fd |
339 | close, closedir, cos, crypt*, defined, delete, |
4e592037 |
340 | die, do, dump*, each, endpwent, eof, eval, exec*, |
341 | exists, exit, exp, fileno, fork*, getc, getlogin, |
342 | getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto, |
343 | grep, hex, import, index, int, join, keys, kill*, |
344 | last, lc, lcfirst, length, local, localtime, log, m//, |
345 | map, mkdir, my, next, no, oct, open, opendir, ord, pack, |
c07a80fd |
346 | pipe, pop, pos, print, printf, push, q//, qq//, qw//, |
4fdae800 |
347 | qx//*, quotemeta, rand, read, readdir, redo, ref, rename, |
a0d0e21e |
348 | require, reset, return, reverse, rewinddir, rindex, |
e518068a |
349 | rmdir, s///, scalar, seek, seekdir, select(internal), |
350 | select (system call)*, setpwent, shift, sin, sleep, |
351 | sort, splice, split, sprintf, sqrt, srand, stat, |
352 | study, substr, sysread, system*, syswrite, tell, |
353 | telldir, tie, time, times*, tr///, uc, ucfirst, umask, |
354 | undef, unlink*, unpack, untie, unshift, use, utime*, |
355 | values, vec, wait, waitpid*, wantarray, warn, write, y/// |
a0d0e21e |
356 | |
357 | The following functions were not implemented in the VMS port, |
358 | and calling them produces a fatal error (usually) or |
359 | undefined behavior (rarely, we hope): |
360 | |
35b2760a |
361 | chroot, dbmclose, dbmopen, flock, |
c07a80fd |
362 | getpgrp, getppid, getpriority, getgrent, getgrgid, |
363 | getgrnam, setgrent, endgrent, ioctl, link, lstat, |
364 | msgctl, msgget, msgsend, msgrcv, readlink, semctl, |
365 | semget, semop, setpgrp, setpriority, shmctl, shmget, |
bf99883d |
366 | shmread, shmwrite, socketpair, symlink, syscall |
367 | |
35b2760a |
368 | The following functions are available on Perls compiled with Dec C |
369 | 5.2 or greater and running VMS 7.0 or greater: |
bf99883d |
370 | |
371 | truncate |
a0d0e21e |
372 | |
35b2760a |
373 | The following functions are available on Perls built on VMS 7.2 or |
374 | greater: |
375 | |
376 | fcntl (without locking) |
377 | |
a0d0e21e |
378 | The following functions may or may not be implemented, |
379 | depending on what type of socket support you've built into |
748a9306 |
380 | your copy of Perl: |
4e592037 |
381 | |
a0d0e21e |
382 | accept, bind, connect, getpeername, |
383 | gethostbyname, getnetbyname, getprotobyname, |
384 | getservbyname, gethostbyaddr, getnetbyaddr, |
385 | getprotobynumber, getservbyport, gethostent, |
386 | getnetent, getprotoent, getservent, sethostent, |
387 | setnetent, setprotoent, setservent, endhostent, |
388 | endnetent, endprotoent, endservent, getsockname, |
c07a80fd |
389 | getsockopt, listen, recv, select(system call)*, |
390 | send, setsockopt, shutdown, socket |
a0d0e21e |
391 | |
55497cff |
392 | =over 4 |
a0d0e21e |
393 | |
394 | =item File tests |
395 | |
748a9306 |
396 | The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>, |
397 | C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as |
398 | advertised. The return values for C<-r>, C<-w>, and C<-x> |
399 | tell you whether you can actually access the file; this may |
400 | not reflect the UIC-based file protections. Since real and |
401 | effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>, |
402 | and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>. |
403 | Similarly, several other tests, including C<-A>, C<-g>, C<-k>, |
404 | C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under |
405 | VMS, and the values returned by these tests reflect whatever |
406 | your CRTL C<stat()> routine does to the equivalent bits in the |
407 | st_mode field. Finally, C<-d> returns true if passed a device |
408 | specification without an explicit directory (e.g. C<DUA1:>), as |
409 | well as if passed a directory. |
410 | |
4e592037 |
411 | Note: Some sites have reported problems when using the file-access |
412 | tests (C<-r>, C<-w>, and C<-x>) on files accessed via DEC's DFS. |
413 | Specifically, since DFS does not currently provide access to the |
414 | extended file header of files on remote volumes, attempts to |
415 | examine the ACL fail, and the file tests will return false, |
416 | with C<$!> indicating that the file does not exist. You can |
417 | use C<stat> on these files, since that checks UIC-based protection |
418 | only, and then manually check the appropriate bits, as defined by |
419 | your C compiler's F<stat.h>, in the mode value it returns, if you |
420 | need an approximation of the file's protections. |
421 | |
4fdae800 |
422 | =item backticks |
423 | |
424 | Backticks create a subprocess, and pass the enclosed string |
425 | to it for execution as a DCL command. Since the subprocess is |
426 | created directly via C<lib$spawn()>, any valid DCL command string |
427 | may be specified. |
428 | |
748a9306 |
429 | =item binmode FILEHANDLE |
430 | |
1c9f8daa |
431 | The C<binmode> operator will attempt to insure that no translation |
432 | of carriage control occurs on input from or output to this filehandle. |
433 | Since this involves reopening the file and then restoring its |
434 | file position indicator, if this function returns FALSE, the |
435 | underlying filehandle may no longer point to an open file, or may |
436 | point to a different position in the file than before C<binmode> |
437 | was called. |
438 | |
439 | Note that C<binmode> is generally not necessary when using normal |
440 | filehandles; it is provided so that you can control I/O to existing |
441 | record-structured files when necessary. You can also use the |
442 | C<vmsfopen> function in the VMS::Stdio extension to gain finer |
443 | control of I/O to files and devices with different record structures. |
a0d0e21e |
444 | |
c07a80fd |
445 | =item crypt PLAINTEXT, USER |
446 | |
447 | The C<crypt> operator uses the C<sys$hash_password> system |
448 | service to generate the hashed representation of PLAINTEXT. |
449 | If USER is a valid username, the algorithm and salt values |
450 | are taken from that user's UAF record. If it is not, then |
451 | the preferred algorithm and a salt of 0 are used. The |
452 | quadword encrypted value is returned as an 8-character string. |
453 | |
454 | The value returned by C<crypt> may be compared against |
455 | the encrypted password from the UAF returned by the C<getpw*> |
456 | functions, in order to authenticate users. If you're |
457 | going to do this, remember that the encrypted password in |
458 | the UAF was generated using uppercase username and |
459 | password strings; you'll have to upcase the arguments to |
460 | C<crypt> to insure that you'll get the proper value: |
461 | |
376ae1f1 |
462 | sub validate_passwd { |
463 | my($user,$passwd) = @_; |
464 | my($pwdhash); |
465 | if ( !($pwdhash = (getpwnam($user))[1]) || |
466 | $pwdhash ne crypt("\U$passwd","\U$name") ) { |
467 | intruder_alert($name); |
468 | } |
469 | return 1; |
c07a80fd |
470 | } |
c07a80fd |
471 | |
4e592037 |
472 | =item dump |
473 | |
474 | Rather than causing Perl to abort and dump core, the C<dump> |
475 | operator invokes the VMS debugger. If you continue to |
476 | execute the Perl program under the debugger, control will |
477 | be transferred to the label specified as the argument to |
478 | C<dump>, or, if no label was specified, back to the |
479 | beginning of the program. All other state of the program |
480 | (I<e.g.> values of variables, open file handles) are not |
481 | affected by calling C<dump>. |
482 | |
748a9306 |
483 | =item exec LIST |
a0d0e21e |
484 | |
748a9306 |
485 | The C<exec> operator behaves in one of two different ways. |
486 | If called after a call to C<fork>, it will invoke the CRTL |
487 | C<execv()> routine, passing its arguments to the subprocess |
488 | created by C<fork> for execution. In this case, it is |
489 | subject to all limitations that affect C<execv()>. (In |
a0d0e21e |
490 | particular, this usually means that the command executed in |
491 | the subprocess must be an image compiled from C source code, |
492 | and that your options for passing file descriptors and signal |
493 | handlers to the subprocess are limited.) |
494 | |
748a9306 |
495 | If the call to C<exec> does not follow a call to C<fork>, it |
496 | will cause Perl to exit, and to invoke the command given as |
497 | an argument to C<exec> via C<lib$do_command>. If the argument |
aa779de1 |
498 | begins with '@' or '$' (other than as part of a filespec), then it |
a0d0e21e |
499 | is executed as a DCL command. Otherwise, the first token on |
500 | the command line is treated as the filespec of an image to |
501 | run, and an attempt is made to invoke it (using F<.Exe> and |
502 | the process defaults to expand the filespec) and pass the |
c93fa817 |
503 | rest of C<exec>'s argument to it as parameters. If the token |
504 | has no file type, and matches a file with null type, then an |
505 | attempt is made to determine whether the file is an executable |
506 | image which should be invoked using C<MCR> or a text file which |
507 | should be passed to DCL as a command procedure. |
a0d0e21e |
508 | |
748a9306 |
509 | You can use C<exec> in both ways within the same script, as |
510 | long as you call C<fork> and C<exec> in pairs. Perl |
511 | keeps track of how many times C<fork> and C<exec> have been |
512 | called, and will call the CRTL C<execv()> routine if there have |
513 | previously been more calls to C<fork> than to C<exec>. |
a0d0e21e |
514 | |
515 | =item fork |
516 | |
748a9306 |
517 | The C<fork> operator works in the same way as the CRTL |
518 | C<vfork()> routine, which is quite different under VMS than |
519 | under Unix. Specifically, while C<fork> returns 0 after it |
520 | is called and the subprocess PID after C<exec> is called, in |
a0d0e21e |
521 | both cases the thread of execution is within the parent |
522 | process, so there is no opportunity to perform operations in |
748a9306 |
523 | the subprocess before calling C<exec>. |
a0d0e21e |
524 | |
748a9306 |
525 | In general, the use of C<fork> and C<exec> to create |
9bc98430 |
526 | subprocesses is not recommended under VMS; wherever possible, |
748a9306 |
527 | use the C<system> operator or piped filehandles instead. |
528 | |
529 | =item getpwent |
c07a80fd |
530 | |
748a9306 |
531 | =item getpwnam |
c07a80fd |
532 | |
748a9306 |
533 | =item getpwuid |
534 | |
535 | These operators obtain the information described in L<perlfunc>, |
536 | if you have the privileges necessary to retrieve the named user's |
537 | UAF information via C<sys$getuai>. If not, then only the C<$name>, |
538 | C<$uid>, and C<$gid> items are returned. The C<$dir> item contains |
539 | the login directory in VMS syntax, while the C<$comment> item |
540 | contains the login directory in Unix syntax. The C<$gcos> item |
541 | contains the owner field from the UAF record. The C<$quota> |
542 | item is not used. |
a0d0e21e |
543 | |
e518068a |
544 | =item gmtime |
545 | |
546 | The C<gmtime> operator will function properly if you have a |
547 | working CRTL C<gmtime()> routine, or if the logical name |
548 | SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds |
549 | which must be added to UTC to yield local time. (This logical |
550 | name is defined automatically if you are running a version of |
551 | VMS with built-in UTC support.) If neither of these cases is |
552 | true, a warning message is printed, and C<undef> is returned. |
553 | |
554 | =item kill |
555 | |
39aca757 |
556 | In most cases, C<kill> is implemented via the CRTL's C<kill()> |
e518068a |
557 | function, so it will behave according to that function's |
558 | documentation. If you send a SIGKILL, however, the $DELPRC system |
10a676f8 |
559 | service is called directly. This insures that the target |
e518068a |
560 | process is actually deleted, if at all possible. (The CRTL's C<kill()> |
561 | function is presently implemented via $FORCEX, which is ignored by |
562 | supervisor-mode images like DCL.) |
563 | |
564 | Also, negative signal values don't do anything special under |
565 | VMS; they're just converted to the corresponding positive value. |
566 | |
4fdae800 |
567 | =item qx// |
568 | |
569 | See the entry on C<backticks> above. |
570 | |
e518068a |
571 | =item select (system call) |
572 | |
573 | If Perl was not built with socket support, the system call |
574 | version of C<select> is not available at all. If socket |
575 | support is present, then the system call version of |
576 | C<select> functions only for file descriptors attached |
577 | to sockets. It will not provide information about regular |
578 | files or pipes, since the CRTL C<select()> routine does not |
579 | provide this functionality. |
580 | |
748a9306 |
581 | =item stat EXPR |
a0d0e21e |
582 | |
748a9306 |
583 | Since VMS keeps track of files according to a different scheme |
584 | than Unix, it's not really possible to represent the file's ID |
585 | in the C<st_dev> and C<st_ino> fields of a C<struct stat>. Perl |
586 | tries its best, though, and the values it uses are pretty unlikely |
587 | to be the same for two different files. We can't guarantee this, |
588 | though, so caveat scriptor. |
589 | |
590 | =item system LIST |
591 | |
592 | The C<system> operator creates a subprocess, and passes its |
a0d0e21e |
593 | arguments to the subprocess for execution as a DCL command. |
e518068a |
594 | Since the subprocess is created directly via C<lib$spawn()>, any |
aa779de1 |
595 | valid DCL command string may be specified. If the string begins with |
596 | '@', it is treated as a DCL command unconditionally. Otherwise, if |
597 | the first token contains a character used as a delimiter in file |
598 | specification (e.g. C<:> or C<]>), an attempt is made to expand it |
599 | using a default type of F<.Exe> and the process defaults, and if |
600 | successful, the resulting file is invoked via C<MCR>. This allows you |
601 | to invoke an image directly simply by passing the file specification |
c93fa817 |
602 | to C<system>, a common Unixish idiom. If the token has no file type, |
603 | and matches a file with null type, then an attempt is made to |
604 | determine whether the file is an executable image which should be |
605 | invoked using C<MCR> or a text file which should be passed to DCL |
606 | as a command procedure. |
607 | |
608 | If LIST consists of the empty string, C<system> spawns an |
a2293a43 |
609 | interactive DCL subprocess, in the same fashion as typing |
c93fa817 |
610 | B<SPAWN> at the DCL prompt. |
611 | |
748a9306 |
612 | Perl waits for the subprocess to complete before continuing |
4fdae800 |
613 | execution in the current process. As described in L<perlfunc>, |
614 | the return value of C<system> is a fake "status" which follows |
c6966fea |
615 | POSIX semantics unless the pragma C<use vmsish 'status'> is in |
1b0c4952 |
616 | effect; see the description of C<$?> in this document for more |
617 | detail. |
a0d0e21e |
618 | |
1c9f8daa |
619 | =item time |
620 | |
621 | The value returned by C<time> is the offset in seconds from |
622 | 01-JAN-1970 00:00:00 (just like the CRTL's times() routine), in order |
623 | to make life easier for code coming in from the POSIX/Unix world. |
624 | |
a0d0e21e |
625 | =item times |
626 | |
748a9306 |
627 | The array returned by the C<times> operator is divided up |
628 | according to the same rules the CRTL C<times()> routine. |
a0d0e21e |
629 | Therefore, the "system time" elements will always be 0, since |
630 | there is no difference between "user time" and "system" time |
39aca757 |
631 | under VMS, and the time accumulated by a subprocess may or may |
a0d0e21e |
632 | not appear separately in the "child time" field, depending on |
748a9306 |
633 | whether L<times> keeps track of subprocesses separately. Note |
634 | especially that the VAXCRTL (at least) keeps track only of |
635 | subprocesses spawned using L<fork> and L<exec>; it will not |
a2293a43 |
636 | accumulate the times of subprocesses spawned via pipes, L<system>, |
748a9306 |
637 | or backticks. |
638 | |
16d20bd9 |
639 | =item unlink LIST |
640 | |
641 | C<unlink> will delete the highest version of a file only; in |
642 | order to delete all versions, you need to say |
39aca757 |
643 | |
35b2760a |
644 | 1 while unlink LIST; |
39aca757 |
645 | |
16d20bd9 |
646 | You may need to make this change to scripts written for a |
647 | Unix system which expect that after a call to C<unlink>, |
648 | no files with the names passed to C<unlink> will exist. |
4633a7c4 |
649 | (Note: This can be changed at compile time; if you |
650 | C<use Config> and C<$Config{'d_unlink_all_versions'}> is |
651 | C<define>, then C<unlink> will delete all versions of a |
652 | file on the first call.) |
16d20bd9 |
653 | |
654 | C<unlink> will delete a file if at all possible, even if it |
655 | requires changing file protection (though it won't try to |
656 | change the protection of the parent directory). You can tell |
657 | whether you've got explicit delete access to a file by using the |
658 | C<VMS::Filespec::candelete> operator. For instance, in order |
659 | to delete only files to which you have delete access, you could |
660 | say something like |
4e592037 |
661 | |
16d20bd9 |
662 | sub safe_unlink { |
663 | my($file,$num); |
664 | foreach $file (@_) { |
665 | next unless VMS::Filespec::candelete($file); |
666 | $num += unlink $file; |
667 | } |
668 | $num; |
669 | } |
4e592037 |
670 | |
671 | (or you could just use C<VMS::Stdio::remove>, if you've installed |
672 | the VMS::Stdio extension distributed with Perl). If C<unlink> has to |
673 | change the file protection to delete the file, and you interrupt it |
674 | in midstream, the file may be left intact, but with a changed ACL |
675 | allowing you delete access. |
16d20bd9 |
676 | |
748a9306 |
677 | =item utime LIST |
678 | |
679 | Since ODS-2, the VMS file structure for disk files, does not keep |
680 | track of access times, this operator changes only the modification |
681 | time of the file (VMS revision date). |
682 | |
683 | =item waitpid PID,FLAGS |
684 | |
39aca757 |
685 | If PID is a subprocess started by a piped C<open()> (see L<open>), |
376ae1f1 |
686 | C<waitpid> will wait for that subprocess, and return its final status |
687 | value in C<$?>. If PID is a subprocess created in some other way (e.g. |
688 | SPAWNed before Perl was invoked), C<waitpid> will simply check once per |
689 | second whether the process has completed, and return when it has. (If |
690 | PID specifies a process that isn't a subprocess of the current process, |
691 | and you invoked Perl with the C<-w> switch, a warning will be issued.) |
35b2760a |
692 | |
693 | Returns PID on success, -1 on error. The FLAGS argument is ignored |
694 | in all cases. |
a0d0e21e |
695 | |
55497cff |
696 | =back |
697 | |
a5f75d66 |
698 | =head1 Perl variables |
699 | |
55497cff |
700 | The following VMS-specific information applies to the indicated |
701 | "special" Perl variables, in addition to the general information |
a2293a43 |
702 | in L<perlvar>. Where there is a conflict, this information |
55497cff |
703 | takes precedence. |
704 | |
705 | =over 4 |
706 | |
a5f75d66 |
707 | =item %ENV |
708 | |
f675dbe5 |
709 | The operation of the C<%ENV> array depends on the translation |
710 | of the logical name F<PERL_ENV_TABLES>. If defined, it should |
711 | be a search list, each element of which specifies a location |
712 | for C<%ENV> elements. If you tell Perl to read or set the |
713 | element C<$ENV{>I<name>C<}>, then Perl uses the translations of |
714 | F<PERL_ENV_TABLES> as follows: |
715 | |
716 | =over 4 |
717 | |
718 | =item CRTL_ENV |
719 | |
720 | This string tells Perl to consult the CRTL's internal C<environ> |
721 | array of key-value pairs, using I<name> as the key. In most cases, |
722 | this contains only a few keys, but if Perl was invoked via the C |
723 | C<exec[lv]e()> function, as is the case for CGI processing by some |
724 | HTTP servers, then the C<environ> array may have been populated by |
725 | the calling program. |
726 | |
727 | =item CLISYM_[LOCAL] |
728 | |
729 | A string beginning with C<CLISYM_>tells Perl to consult the CLI's |
730 | symbol tables, using I<name> as the name of the symbol. When reading |
731 | an element of C<%ENV>, the local symbol table is scanned first, followed |
732 | by the global symbol table.. The characters following C<CLISYM_> are |
733 | significant when an element of C<%ENV> is set or deleted: if the |
734 | complete string is C<CLISYM_LOCAL>, the change is made in the local |
39aca757 |
735 | symbol table; otherwise the global symbol table is changed. |
f675dbe5 |
736 | |
737 | =item Any other string |
738 | |
739 | If an element of F<PERL_ENV_TABLES> translates to any other string, |
740 | that string is used as the name of a logical name table, which is |
741 | consulted using I<name> as the logical name. The normal search |
742 | order of access modes is used. |
743 | |
744 | =back |
745 | |
746 | F<PERL_ENV_TABLES> is translated once when Perl starts up; any changes |
747 | you make while Perl is running do not affect the behavior of C<%ENV>. |
748 | If F<PERL_ENV_TABLES> is not defined, then Perl defaults to consulting |
749 | first the logical name tables specified by F<LNM$FILE_DEV>, and then |
750 | the CRTL C<environ> array. |
751 | |
752 | In all operations on %ENV, the key string is treated as if it |
753 | were entirely uppercase, regardless of the case actually |
754 | specified in the Perl expression. |
755 | |
756 | When an element of C<%ENV> is read, the locations to which |
757 | F<PERL_ENV_TABLES> points are checked in order, and the value |
758 | obtained from the first successful lookup is returned. If the |
759 | name of the C<%ENV> element contains a semi-colon, it and |
760 | any characters after it are removed. These are ignored when |
761 | the CRTL C<environ> array or a CLI symbol table is consulted. |
762 | However, the name is looked up in a logical name table, the |
763 | suffix after the semi-colon is treated as the translation index |
764 | to be used for the lookup. This lets you look up successive values |
765 | for search list logical names. For instance, if you say |
a5f75d66 |
766 | |
767 | $ Define STORY once,upon,a,time,there,was |
768 | $ perl -e "for ($i = 0; $i <= 6; $i++) " - |
740ce14c |
769 | _$ -e "{ print $ENV{'story;'.$i},' '}" |
a5f75d66 |
770 | |
f675dbe5 |
771 | Perl will print C<ONCE UPON A TIME THERE WAS>, assuming, of course, |
772 | that F<PERL_ENV_TABLES> is set up so that the logical name C<story> |
773 | is found, rather than a CLI symbol or CRTL C<environ> element with |
774 | the same name. |
775 | |
3eeba6fb |
776 | When an element of C<%ENV> is set to a defined string, the |
f675dbe5 |
777 | corresponding definition is made in the location to which the |
778 | first translation of F<PERL_ENV_TABLES> points. If this causes a |
779 | logical name to be created, it is defined in supervisor mode. |
3eeba6fb |
780 | (The same is done if an existing logical name was defined in |
781 | executive or kernel mode; an existing user or supervisor mode |
782 | logical name is reset to the new value.) If the value is an empty |
783 | string, the logical name's translation is defined as a single NUL |
784 | (ASCII 00) character, since a logical name cannot translate to a |
785 | zero-length string. (This restriction does not apply to CLI symbols |
786 | or CRTL C<environ> values; they are set to the empty string.) |
f675dbe5 |
787 | An element of the CRTL C<environ> array can be set only if your |
788 | copy of Perl knows about the CRTL's C<setenv()> function. (This is |
789 | present only in some versions of the DECCRTL; check C<$Config{d_setenv}> |
790 | to see whether your copy of Perl was built with a CRTL that has this |
791 | function.) |
39aca757 |
792 | |
3eeba6fb |
793 | When an element of C<%ENV> is set to C<undef>, |
f675dbe5 |
794 | the element is looked up as if it were being read, and if it is |
795 | found, it is deleted. (An item "deleted" from the CRTL C<environ> |
796 | array is set to the empty string; this can only be done if your |
797 | copy of Perl knows about the CRTL C<setenv()> function.) Using |
798 | C<delete> to remove an element from C<%ENV> has a similar effect, |
799 | but after the element is deleted, another attempt is made to |
800 | look up the element, so an inner-mode logical name or a name in |
801 | another location will replace the logical name just deleted. |
3eeba6fb |
802 | In either case, only the first value found searching PERL_ENV_TABLES |
803 | is altered. It is not possible at present to define a search list |
804 | logical name via %ENV. |
f675dbe5 |
805 | |
806 | The element C<$ENV{DEFAULT}> is special: when read, it returns |
807 | Perl's current default device and directory, and when set, it |
808 | resets them, regardless of the definition of F<PERL_ENV_TABLES>. |
809 | It cannot be cleared or deleted; attempts to do so are silently |
810 | ignored. |
b7b1864f |
811 | |
812 | Note that if you want to pass on any elements of the |
813 | C-local environ array to a subprocess which isn't |
814 | started by fork/exec, or isn't running a C program, you |
815 | can "promote" them to logical names in the current |
816 | process, which will then be inherited by all subprocesses, |
817 | by saying |
818 | |
819 | foreach my $key (qw[C-local keys you want promoted]) { |
376ae1f1 |
820 | my $temp = $ENV{$key}; # read from C-local array |
821 | $ENV{$key} = $temp; # and define as logical name |
b7b1864f |
822 | } |
823 | |
824 | (You can't just say C<$ENV{$key} = $ENV{$key}>, since the |
825 | Perl optimizer is smart enough to elide the expression.) |
a5f75d66 |
826 | |
6be8f7a6 |
827 | Don't try to clear C<%ENV> by saying C<%ENV = ();>, it will throw |
828 | a fatal error. This is equivalent to doing the following from DCL: |
829 | |
830 | DELETE/LOGICAL * |
831 | |
832 | You can imagine how bad things would be if, for example, the SYS$MANAGER |
833 | or SYS$SYSTEM logicals were deleted. |
4a0d0822 |
834 | |
740ce14c |
835 | At present, the first time you iterate over %ENV using |
edc7bc49 |
836 | C<keys>, or C<values>, you will incur a time penalty as all |
837 | logical names are read, in order to fully populate %ENV. |
838 | Subsequent iterations will not reread logical names, so they |
839 | won't be as slow, but they also won't reflect any changes |
f675dbe5 |
840 | to logical name tables caused by other programs. |
841 | |
842 | You do need to be careful with the logicals representing process-permanent |
843 | files, such as C<SYS$INPUT> and C<SYS$OUTPUT>. The translations for these |
844 | logicals are prepended with a two-byte binary value (0x1B 0x00) that needs to be |
39aca757 |
845 | stripped off if you want to use it. (In previous versions of Perl it wasn't |
f675dbe5 |
846 | possible to get the values of these logicals, as the null byte acted as an |
847 | end-of-string marker) |
a5f75d66 |
848 | |
a5f75d66 |
849 | =item $! |
850 | |
851 | The string value of C<$!> is that returned by the CRTL's |
852 | strerror() function, so it will include the VMS message for |
853 | VMS-specific errors. The numeric value of C<$!> is the |
854 | value of C<errno>, except if errno is EVMSERR, in which |
855 | case C<$!> contains the value of vaxc$errno. Setting C<$!> |
4e592037 |
856 | always sets errno to the value specified. If this value is |
857 | EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-NOMSG), so |
858 | that the string value of C<$!> won't reflect the VMS error |
859 | message from before C<$!> was set. |
860 | |
861 | =item $^E |
862 | |
863 | This variable provides direct access to VMS status values |
864 | in vaxc$errno, which are often more specific than the |
865 | generic Unix-style error messages in C<$!>. Its numeric value |
866 | is the value of vaxc$errno, and its string value is the |
867 | corresponding VMS message string, as retrieved by sys$getmsg(). |
868 | Setting C<$^E> sets vaxc$errno to the value specified. |
869 | |
4fdae800 |
870 | =item $? |
871 | |
872 | The "status value" returned in C<$?> is synthesized from the |
873 | actual exit status of the subprocess in a way that approximates |
874 | POSIX wait(5) semantics, in order to allow Perl programs to |
875 | portably test for successful completion of subprocesses. The |
876 | low order 8 bits of C<$?> are always 0 under VMS, since the |
877 | termination status of a process may or may not have been |
878 | generated by an exception. The next 8 bits are derived from |
39aca757 |
879 | the severity portion of the subprocess' exit status: if the |
4fdae800 |
880 | severity was success or informational, these bits are all 0; |
9bc98430 |
881 | if the severity was warning, they contain a value of 1; if the |
882 | severity was error or fatal error, they contain the actual |
883 | severity bits, which turns out to be a value of 2 for error |
884 | and 4 for fatal error. |
885 | |
4fdae800 |
886 | As a result, C<$?> will always be zero if the subprocess' exit |
887 | status indicated successful completion, and non-zero if a |
9bc98430 |
888 | warning or error occurred. Conversely, when setting C<$?> in |
889 | an END block, an attempt is made to convert the POSIX value |
890 | into a native status intelligible to the operating system upon |
891 | exiting Perl. What this boils down to is that setting C<$?> |
892 | to zero results in the generic success value SS$_NORMAL, and |
893 | setting C<$?> to a non-zero value results in the generic |
894 | failure status SS$_ABORT. See also L<perlport/exit>. |
4fdae800 |
895 | |
1b0c4952 |
896 | The pragma C<use vmsish 'status'> makes C<$?> reflect the actual |
9bc98430 |
897 | VMS exit status instead of the default emulation of POSIX status |
898 | described above. This pragma also disables the conversion of |
899 | non-zero values to SS$_ABORT when setting C<$?> in an END |
900 | block (but zero will still be converted to SS$_NORMAL). |
4fdae800 |
901 | |
4e592037 |
902 | =item $| |
903 | |
904 | Setting C<$|> for an I/O stream causes data to be flushed |
905 | all the way to disk on each write (I<i.e.> not just to |
906 | the underlying RMS buffers for a file). In other words, |
907 | it's equivalent to calling fflush() and fsync() from C. |
a5f75d66 |
908 | |
55497cff |
909 | =back |
910 | |
bf99883d |
911 | =head1 Standard modules with VMS-specific differences |
912 | |
913 | =head2 SDBM_File |
914 | |
270c2ced |
915 | SDBM_File works properly on VMS. It has, however, one minor |
4a4eefd0 |
916 | difference. The database directory file created has a F<.sdbm_dir> |
917 | extension rather than a F<.dir> extension. F<.dir> files are VMS filesystem |
bf99883d |
918 | directory files, and using them for other purposes could cause unacceptable |
919 | problems. |
920 | |
748a9306 |
921 | =head1 Revision date |
a0d0e21e |
922 | |
1506e54c |
923 | This document was last updated on 01-May-2002, for Perl 5, |
9bc98430 |
924 | patchlevel 8. |
e518068a |
925 | |
926 | =head1 AUTHOR |
927 | |
376ae1f1 |
928 | Charles Bailey bailey@cor.newman.upenn.edu |
929 | Craig Berry craigberry@mac.com |
930 | Dan Sugalski dan@sidhe.org |