1PERLVMS(1) Perl Programmers Reference Guide PERLVMS(1)
2
6 perlvms - VMS-specific documentation for Perl
7
9 Gathered below are notes describing details of Perl 5's behavior on
10 VMS. They are a supplement to the regular Perl 5 documentation, so we
11 have focussed on the ways in which Perl 5 functions differently under
12 VMS than it does under Unix, and on the interactions between Perl and
13 the rest of the operating system. We haven't tried to duplicate
14 complete descriptions of Perl features from the main Perl
15 documentation, which can be found in the [.pod] subdirectory of the
16 Perl distribution.
17 We hope these notes will save you from confusion and lost sleep when
19 writing Perl scripts on VMS. If you find we've missed something you
20 think should appear here, please don't hesitate to drop a line to
21 vmsperl@perl.org.
22
24 Directions for building and installing Perl 5 can be found in the file
25 README.vms in the main source directory of the Perl distribution.
26
28 Core Images
29 During the build process, three Perl images are produced. Miniperl.Exe
30 is an executable image which contains all of the basic functionality of
31 Perl, but cannot take advantage of Perl XS extensions and has a hard-
32 wired list of library locations for loading pure-Perl modules. It is
33 used extensively to build and test Perl and various extensions, but is
34 not installed.
35 Most of the complete Perl resides in the shareable image PerlShr.Exe,
37 which provides a core to which the Perl executable image and all Perl
38 extensions are linked. It is generally located via the logical name
39 PERLSHR. While it's possible to put the image in SYS$SHARE to make it
40 loadable, that's not recommended. And while you may wish to INSTALL the
41 image for performance reasons, you should not install it with
42 privileges; if you do, the result will not be what you expect as image
43 privileges are disabled during Perl start-up.
44 Finally, Perl.Exe is an executable image containing the main entry
46 point for Perl, as well as some initialization code. It should be
47 placed in a public directory, and made world executable. In order to
48 run Perl with command line arguments, you should define a foreign
49 command to invoke this image.
50 Perl Extensions
52 Perl extensions are packages which provide both XS and Perl code to add
53 new functionality to perl. (XS is a meta-language which simplifies
54 writing C code which interacts with Perl, see perlxs for more details.)
55 The Perl code for an extension is treated like any other library module
56 - it's made available in your script through the appropriate "use" or
57 "require" statement, and usually defines a Perl package containing the
58 extension.
59 The portion of the extension provided by the XS code may be connected
61 to the rest of Perl in either of two ways. In the static
62 configuration, the object code for the extension is linked directly
63 into PerlShr.Exe, and is initialized whenever Perl is invoked. In the
64 dynamic configuration, the extension's machine code is placed into a
65 separate shareable image, which is mapped by Perl's DynaLoader when the
66 extension is "use"d or "require"d in your script. This allows you to
67 maintain the extension as a separate entity, at the cost of keeping
68 track of the additional shareable image. Most extensions can be set up
69 as either static or dynamic.
70 The source code for an extension usually resides in its own directory.
72 At least three files are generally provided: Extshortname.xs (where
73 Extshortname is the portion of the extension's name following the last
74 "::"), containing the XS code, Extshortname.pm, the Perl library module
75 for the extension, and Makefile.PL, a Perl script which uses the
76 "MakeMaker" library modules supplied with Perl to generate a
77 Descrip.MMS file for the extension.
78 Installing static extensions
80 Since static extensions are incorporated directly into PerlShr.Exe,
81 you'll have to rebuild Perl to incorporate a new extension. You should
82 edit the main Descrip.MMS or Makefile you use to build Perl, adding the
83 extension's name to the "ext" macro, and the extension's object file to
84 the "extobj" macro. You'll also need to build the extension's object
85 file, either by adding dependencies to the main Descrip.MMS, or using a
86 separate Descrip.MMS for the extension. Then, rebuild PerlShr.Exe to
87 incorporate the new code.
88 Finally, you'll need to copy the extension's Perl library module to the
90 [.Extname] subdirectory under one of the directories in @INC, where
91 Extname is the name of the extension, with all "::" replaced by "."
92 (e.g. the library module for extension Foo::Bar would be copied to a
93 [.Foo.Bar] subdirectory).
94 Installing dynamic extensions
96 In general, the distributed kit for a Perl extension includes a file
97 named Makefile.PL, which is a Perl program which is used to create a
98 Descrip.MMS file which can be used to build and install the files
99 required by the extension. The kit should be unpacked into a directory
100 tree not under the main Perl source directory, and the procedure for
101 building the extension is simply
102 $ perl Makefile.PL ! Create Descrip.MMS
104 $ mmk ! Build necessary files
105 $ mmk test ! Run test code, if supplied
106 $ mmk install ! Install into public Perl tree
107 VMS support for this process in the current release of Perl is
109 sufficient to handle most extensions. (See the MakeMaker documentation
110 for more details on installation options for extensions.)
111 · the [.Lib.Auto.Arch$PVersExtname] subdirectory of one of the
113 directories in @INC (where PVers is the version of Perl you're
114 using, as supplied in $], with '.' converted to '_'), or
115 · one of the directories in @INC, or
117 · a directory which the extensions Perl library module passes to the
119 DynaLoader when asking it to map the shareable image, or
120 · Sys$Share or Sys$Library.
122 If the shareable image isn't in any of these places, you'll need to
124 define a logical name Extshortname, where Extshortname is the portion
125 of the extension's name after the last "::", which translates to the
126 full file specification of the shareable image.
127
129 Syntax
130 We have tried to make Perl aware of both VMS-style and Unix-style file
131 specifications wherever possible. You may use either style, or both,
132 on the command line and in scripts, but you may not combine the two
133 styles within a single file specification. VMS Perl interprets Unix
134 pathnames in much the same way as the CRTL (e.g. the first component of
135 an absolute path is read as the device name for the VMS file
136 specification). There are a set of functions provided in the
137 "VMS::Filespec" package for explicit interconversion between VMS and
138 Unix syntax; its documentation provides more details.
139 We've tried to minimize the dependence of Perl library modules on Unix
141 syntax, but you may find that some of these, as well as some scripts
142 written for Unix systems, will require that you use Unix syntax, since
143 they will assume that '/' is the directory separator, etc. If you find
144 instances of this in the Perl distribution itself, please let us know,
145 so we can try to work around them.
146 Also when working on Perl programs on VMS, if you need a syntax in a
148 specific operating system format, then you need either to check the
149 appropriate DECC$ feature logical, or call a conversion routine to
150 force it to that format.
151 The feature logical name DECC$FILENAME_UNIX_REPORT modifies traditional
153 Perl behavior in the conversion of file specifications from Unix to VMS
154 format in order to follow the extended character handling rules now
155 expected by the CRTL. Specifically, when this feature is in effect,
156 the "./.../" in a Unix path is now translated to "[.^.^.^.]" instead of
157 the traditional VMS "[...]". To be compatible with what MakeMaker
158 expects, if a VMS path cannot be translated to a Unix path, it is
159 passed through unchanged, so "unixify("[...]")" will return "[...]".
160 There are several ambiguous cases where a conversion routine cannot
162 determine whether an input filename is in Unix format or in VMS format,
163 since now both VMS and Unix file specifications may have characters in
164 them that could be mistaken for syntax delimiters of the other type. So
165 some pathnames simply cannot be used in a mode that allows either type
166 of pathname to be present. Perl will tend to assume that an ambiguous
167 filename is in Unix format.
168 Allowing "." as a version delimiter is simply incompatible with
170 determining whether a pathname is in VMS format or in Unix format with
171 extended file syntax. There is no way to know whether "perl-5.8.6" is
172 a Unix "perl-5.8.6" or a VMS "perl-5.8;6" when passing it to unixify()
173 or vmsify().
174 The DECC$FILENAME_UNIX_REPORT logical name controls how Perl interprets
176 filenames to the extent that Perl uses the CRTL internally for many
177 purposes, and attempts to follow CRTL conventions for reporting
178 filenames. The DECC$FILENAME_UNIX_ONLY feature differs in that it
179 expects all filenames passed to the C run-time to be already in Unix
180 format. This feature is not yet supported in Perl since Perl uses
181 traditional OpenVMS file specifications internally and in the test
182 harness, and it is not yet clear whether this mode will be useful or
183 useable. The feature logical name DECC$POSIX_COMPLIANT_PATHNAMES is
184 new with the RMS Symbolic Link SDK and included with OpenVMS v8.3, but
185 is not yet supported in Perl.
186 Filename Case
188 Perl enables DECC$EFS_CASE_PRESERVE and DECC$ARGV_PARSE_STYLE by
189 default. Note that the latter only takes effect when extended parse is
190 set in the process in which Perl is running. When these features are
191 explicitly disabled in the environment or the CRTL does not support
192 them, Perl follows the traditional CRTL behavior of downcasing command-
193 line arguments and returning file specifications in lower case only.
194 N. B. It is very easy to get tripped up using a mixture of other
196 programs, external utilities, and Perl scripts that are in varying
197 states of being able to handle case preservation. For example, a file
198 created by an older version of an archive utility or a build utility
199 such as MMK or MMS may generate a filename in all upper case even on an
200 ODS-5 volume. If this filename is later retrieved by a Perl script or
201 module in a case preserving environment, that upper case name may not
202 match the mixed-case or lower-case expectations of the Perl code. Your
203 best bet is to follow an all-or-nothing approach to case preservation:
204 either don't use it at all, or make sure your entire toolchain and
205 application environment support and use it.
206 OpenVMS Alpha v7.3-1 and later and all version of OpenVMS I64 support
208 case sensitivity as a process setting (see "SET PROCESS
209 /CASE_LOOKUP=SENSITIVE"). Perl does not currently support case
210 sensitivity on VMS, but it may in the future, so Perl programs should
211 use the "File::Spec->case_tolerant" method to determine the state, and
212 not the $^O variable.
213 Symbolic Links
215 When built on an ODS-5 volume with symbolic links enabled, Perl by
216 default supports symbolic links when the requisite support is available
217 in the filesystem and CRTL (generally 64-bit OpenVMS v8.3 and later).
218 There are a number of limitations and caveats to be aware of when
219 working with symbolic links on VMS. Most notably, the target of a
220 valid symbolic link must be expressed as a Unix-style path and it must
221 exist on a volume visible from your POSIX root (see the "SHOW ROOT"
222 command in DCL help). For further details on symbolic link
223 capabilities and requirements, see chapter 12 of the CRTL manual that
224 ships with OpenVMS v8.3 or later.
225 Wildcard expansion
227 File specifications containing wildcards are allowed both on the
228 command line and within Perl globs (e.g. "<*.c>"). If the wildcard
229 filespec uses VMS syntax, the resultant filespecs will follow VMS
230 syntax; if a Unix-style filespec is passed in, Unix-style filespecs
231 will be returned. Similar to the behavior of wildcard globbing for a
232 Unix shell, one can escape command line wildcards with double quotation
233 marks """ around a perl program command line argument. However, owing
234 to the stripping of """ characters carried out by the C handling of
235 argv you will need to escape a construct such as this one (in a
236 directory containing the files PERL.C, PERL.EXE, PERL.H, and PERL.OBJ):
237 $ perl -e "print join(' ',@ARGV)" perl.*
239 perl.c perl.exe perl.h perl.obj
240 in the following triple quoted manner:
242 $ perl -e "print join(' ',@ARGV)" """perl.*"""
244 perl.*
245 In both the case of unquoted command line arguments or in calls to
247 "glob()" VMS wildcard expansion is performed. (csh-style wildcard
248 expansion is available if you use "File::Glob::glob".) If the wildcard
249 filespec contains a device or directory specification, then the
250 resultant filespecs will also contain a device and directory;
251 otherwise, device and directory information are removed. VMS-style
252 resultant filespecs will contain a full device and directory, while
253 Unix-style resultant filespecs will contain only as much of a directory
254 path as was present in the input filespec. For example, if your
255 default directory is Perl_Root:[000000], the expansion of "[.t]*.*"
256 will yield filespecs like "perl_root:[t]base.dir", while the expansion
257 of "t/*/*" will yield filespecs like "t/base.dir". (This is done to
258 match the behavior of glob expansion performed by Unix shells.)
259 Similarly, the resultant filespec will contain the file version only if
261 one was present in the input filespec.
262 Pipes
264 Input and output pipes to Perl filehandles are supported; the "file
265 name" is passed to lib$spawn() for asynchronous execution. You should
266 be careful to close any pipes you have opened in a Perl script, lest
267 you leave any "orphaned" subprocesses around when Perl exits.
268 You may also use backticks to invoke a DCL subprocess, whose output is
270 used as the return value of the expression. The string between the
271 backticks is handled as if it were the argument to the "system"
272 operator (see below). In this case, Perl will wait for the subprocess
273 to complete before continuing.
274 The mailbox (MBX) that perl can create to communicate with a pipe
276 defaults to a buffer size of 8192 on 64-bit systems, 512 on VAX. The
277 default buffer size is adjustable via the logical name PERL_MBX_SIZE
278 provided that the value falls between 128 and the SYSGEN parameter
279 MAXBUF inclusive. For example, to set the mailbox size to 32767 use
280 "$ENV{'PERL_MBX_SIZE'} = 32767;" and then open and use pipe constructs.
281 An alternative would be to issue the command:
282 $ Define PERL_MBX_SIZE 32767
284 before running your wide record pipe program. A larger value may
286 improve performance at the expense of the BYTLM UAF quota.
287
289 The PERL5LIB and PERLLIB environment elements work as documented in
290 perl, except that the element separator is, by default, '|' instead of
291 ':'. However, when running under a Unix shell as determined by the
292 logical name "GNV$UNIX_SHELL", the separator will be ':' as on Unix
293 systems. The directory specifications may use either VMS or Unix
294 syntax.
295
297 The Perl forked debugger places the debugger commands and output in a
298 separate X-11 terminal window so that commands and output from multiple
299 processes are not mixed together.
300 Perl on VMS supports an emulation of the forked debugger when Perl is
302 run on a VMS system that has X11 support installed.
303 To use the forked debugger, you need to have the default display set to
305 an X-11 Server and some environment variables set that Unix expects.
306 The forked debugger requires the environment variable "TERM" to be
308 "xterm", and the environment variable "DISPLAY" to exist. "xterm" must
309 be in lower case.
310 $define TERM "xterm"
312 $define DISPLAY "hostname:0.0"
314 Currently the value of "DISPLAY" is ignored. It is recommended that it
316 be set to be the hostname of the display, the server and screen in Unix
317 notation. In the future the value of DISPLAY may be honored by Perl
318 instead of using the default display.
319 It may be helpful to always use the forked debugger so that script I/O
321 is separated from debugger I/O. You can force the debugger to be
322 forked by assigning a value to the logical name <PERLDB_PIDS> that is
323 not a process identification number.
324 $define PERLDB_PIDS XXXX
326
328 The PERL_VMS_EXCEPTION_DEBUG being defined as "ENABLE" will cause the
329 VMS debugger to be invoked if a fatal exception that is not otherwise
330 handled is raised. The purpose of this is to allow debugging of
331 internal Perl problems that would cause such a condition.
332 This allows the programmer to look at the execution stack and variables
334 to find out the cause of the exception. As the debugger is being
335 invoked as the Perl interpreter is about to do a fatal exit, continuing
336 the execution in debug mode is usually not practical.
337 Starting Perl in the VMS debugger may change the program execution
339 profile in a way that such problems are not reproduced.
340 The "kill" function can be used to test this functionality from within
342 a program.
343 In typical VMS style, only the first letter of the value of this
345 logical name is actually checked in a case insensitive mode, and it is
346 considered enabled if it is the value "T","1" or "E".
347 This logical name must be defined before Perl is started.
349
351 I/O redirection and backgrounding
352 Perl for VMS supports redirection of input and output on the command
353 line, using a subset of Bourne shell syntax:
354 · "<file" reads stdin from "file",
356 · ">file" writes stdout to "file",
358 · ">>file" appends stdout to "file",
360 · "2>file" writes stderr to "file",
362 · "2>>file" appends stderr to "file", and
364 · "2>&1" redirects stderr to stdout.
366 In addition, output may be piped to a subprocess, using the character
368 '|'. Anything after this character on the command line is passed to a
369 subprocess for execution; the subprocess takes the output of Perl as
370 its input.
371 Finally, if the command line ends with '&', the entire command is run
373 in the background as an asynchronous subprocess.
374 Command line switches
376 The following command line switches behave differently under VMS than
377 described in perlrun. Note also that in order to pass uppercase
378 switches to Perl, you need to enclose them in double-quotes on the
379 command line, since the CRTL downcases all unquoted strings.
380 On newer 64 bit versions of OpenVMS, a process setting now controls if
382 the quoting is needed to preserve the case of command line arguments.
383 -i If the "-i" switch is present but no extension for a backup copy is
385 given, then inplace editing creates a new version of a file; the
386 existing copy is not deleted. (Note that if an extension is given,
387 an existing file is renamed to the backup file, as is the case
388 under other operating systems, so it does not remain as a previous
389 version under the original filename.)
390 -S If the "-S" or "-"S"" switch is present and the script name does
392 not contain a directory, then Perl translates the logical name
393 DCL$PATH as a searchlist, using each translation as a directory in
394 which to look for the script. In addition, if no file type is
395 specified, Perl looks in each directory for a file matching the
396 name specified, with a blank type, a type of .pl, and a type of
397 .com, in that order.
398 -u The "-u" switch causes the VMS debugger to be invoked after the
400 Perl program is compiled, but before it has run. It does not
401 create a core dump file.
402
404 As of the time this document was last revised, the following Perl
405 functions were implemented in the VMS port of Perl (functions marked
406 with * are discussed in more detail below):
407 file tests*, abs, alarm, atan, backticks*, binmode*, bless,
409 caller, chdir, chmod, chown, chomp, chop, chr,
410 close, closedir, cos, crypt*, defined, delete, die, do, dump*,
411 each, endgrent, endpwent, eof, eval, exec*, exists, exit, exp,
412 fileno, flock getc, getgrent*, getgrgid*, getgrnam, getlogin,
413 getppid, getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto,
414 grep, hex, ioctl, import, index, int, join, keys, kill*,
415 last, lc, lcfirst, lchown*, length, link*, local, localtime, log,
416 lstat, m//, map, mkdir, my, next, no, oct, open, opendir, ord,
417 pack, pipe, pop, pos, print, printf, push, q//, qq//, qw//,
418 qx//*, quotemeta, rand, read, readdir, readlink*, redo, ref,
419 rename, require, reset, return, reverse, rewinddir, rindex,
420 rmdir, s///, scalar, seek, seekdir, select(internal),
421 select (system call)*, setgrent, setpwent, shift, sin, sleep,
422 socketpair, sort, splice, split, sprintf, sqrt, srand, stat,
423 study, substr, symlink*, sysread, system*, syswrite, tell,
424 telldir, tie, time, times*, tr///, uc, ucfirst, umask,
425 undef, unlink*, unpack, untie, unshift, use, utime*,
426 values, vec, wait, waitpid*, wantarray, warn, write, y///
427 The following functions were not implemented in the VMS port, and
429 calling them produces a fatal error (usually) or undefined behavior
430 (rarely, we hope):
431 chroot, dbmclose, dbmopen, fork*, getpgrp, getpriority,
433 msgctl, msgget, msgsend, msgrcv, semctl,
434 semget, semop, setpgrp, setpriority, shmctl, shmget,
435 shmread, shmwrite, syscall
436 The following functions are available on Perls compiled with Dec C 5.2
438 or greater and running VMS 7.0 or greater:
439 truncate
441 The following functions are available on Perls built on VMS 7.2 or
443 greater:
444 fcntl (without locking)
446 The following functions may or may not be implemented, depending on
448 what type of socket support you've built into your copy of Perl:
449 accept, bind, connect, getpeername,
451 gethostbyname, getnetbyname, getprotobyname,
452 getservbyname, gethostbyaddr, getnetbyaddr,
453 getprotobynumber, getservbyport, gethostent,
454 getnetent, getprotoent, getservent, sethostent,
455 setnetent, setprotoent, setservent, endhostent,
456 endnetent, endprotoent, endservent, getsockname,
457 getsockopt, listen, recv, select(system call)*,
458 send, setsockopt, shutdown, socket
459 The following function is available on Perls built on 64 bit OpenVMS
461 v8.2 with hard links enabled on an ODS-5 formatted build disk. CRTL
462 support is in principle available as of OpenVMS v7.3-1, and better
463 configuration support could detect this.
464 link
466 The following functions are available on Perls built on 64 bit OpenVMS
468 v8.2 and later. CRTL support is in principle available as of OpenVMS
469 v7.3-2, and better configuration support could detect this.
470 getgrgid, getgrnam, getpwnam, getpwuid,
472 setgrent, ttyname
473 The following functions are available on Perls built on 64 bit OpenVMS
475 v8.2 and later.
476 statvfs, socketpair
478 File tests
480 The tests "-b", "-B", "-c", "-C", "-d", "-e", "-f", "-o", "-M",
481 "-s", "-S", "-t", "-T", and "-z" work as advertised. The return
482 values for "-r", "-w", and "-x" tell you whether you can actually
483 access the file; this may not reflect the UIC-based file
484 protections. Since real and effective UIC don't differ under VMS,
485 "-O", "-R", "-W", and "-X" are equivalent to "-o", "-r", "-w", and
486 "-x". Similarly, several other tests, including "-A", "-g", "-k",
487 "-l", "-p", and "-u", aren't particularly meaningful under VMS, and
488 the values returned by these tests reflect whatever your CRTL
489 "stat()" routine does to the equivalent bits in the st_mode field.
490 Finally, "-d" returns true if passed a device specification without
491 an explicit directory (e.g. "DUA1:"), as well as if passed a
492 directory.
493 There are DECC feature logical names AND ODS-5 volume attributes
495 that also control what values are returned for the date fields.
496 Note: Some sites have reported problems when using the file-access
498 tests ("-r", "-w", and "-x") on files accessed via DEC's DFS.
499 Specifically, since DFS does not currently provide access to the
500 extended file header of files on remote volumes, attempts to
501 examine the ACL fail, and the file tests will return false, with $!
502 indicating that the file does not exist. You can use "stat" on
503 these files, since that checks UIC-based protection only, and then
504 manually check the appropriate bits, as defined by your C
505 compiler's stat.h, in the mode value it returns, if you need an
506 approximation of the file's protections.
507 backticks
509 Backticks create a subprocess, and pass the enclosed string to it
510 for execution as a DCL command. Since the subprocess is created
511 directly via "lib$spawn()", any valid DCL command string may be
512 specified.
513 binmode FILEHANDLE
515 The "binmode" operator will attempt to insure that no translation
516 of carriage control occurs on input from or output to this
517 filehandle. Since this involves reopening the file and then
518 restoring its file position indicator, if this function returns
519 FALSE, the underlying filehandle may no longer point to an open
520 file, or may point to a different position in the file than before
521 "binmode" was called.
522 Note that "binmode" is generally not necessary when using normal
524 filehandles; it is provided so that you can control I/O to existing
525 record-structured files when necessary. You can also use the
526 "vmsfopen" function in the VMS::Stdio extension to gain finer
527 control of I/O to files and devices with different record
528 structures.
529 crypt PLAINTEXT, USER
531 The "crypt" operator uses the "sys$hash_password" system service to
532 generate the hashed representation of PLAINTEXT. If USER is a
533 valid username, the algorithm and salt values are taken from that
534 user's UAF record. If it is not, then the preferred algorithm and
535 a salt of 0 are used. The quadword encrypted value is returned as
536 an 8-character string.
537 The value returned by "crypt" may be compared against the encrypted
539 password from the UAF returned by the "getpw*" functions, in order
540 to authenticate users. If you're going to do this, remember that
541 the encrypted password in the UAF was generated using uppercase
542 username and password strings; you'll have to upcase the arguments
543 to "crypt" to insure that you'll get the proper value:
544 sub validate_passwd {
546 my($user,$passwd) = @_;
547 my($pwdhash);
548 if ( !($pwdhash = (getpwnam($user))[1]) ||
549 $pwdhash ne crypt("\U$passwd","\U$name") ) {
550 intruder_alert($name);
551 }
552 return 1;
553 }
554 die "die" will force the native VMS exit status to be an SS$_ABORT code
556 if neither of the $! or $? status values are ones that would cause
557 the native status to be interpreted as being what VMS classifies as
558 SEVERE_ERROR severity for DCL error handling.
559 When "PERL_VMS_POSIX_EXIT" is active (see "$?" below), the native
561 VMS exit status value will have either one of the $! or $? or $^E
562 or the Unix value 255 encoded into it in a way that the effective
563 original value can be decoded by other programs written in C,
564 including Perl and the GNV package. As per the normal non-VMS
565 behavior of "die" if either $! or $? are non-zero, one of those
566 values will be encoded into a native VMS status value. If both of
567 the Unix status values are 0, and the $^E value is set one of ERROR
568 or SEVERE_ERROR severity, then the $^E value will be used as the
569 exit code as is. If none of the above apply, the Unix value of 255
570 will be encoded into a native VMS exit status value.
571 Please note a significant difference in the behavior of "die" in
573 the "PERL_VMS_POSIX_EXIT" mode is that it does not force a VMS
574 SEVERE_ERROR status on exit. The Unix exit values of 2 through 255
575 will be encoded in VMS status values with severity levels of
576 SUCCESS. The Unix exit value of 1 will be encoded in a VMS status
577 value with a severity level of ERROR. This is to be compatible
578 with how the VMS C library encodes these values.
579 The minimum severity level set by "die" in "PERL_VMS_POSIX_EXIT"
581 mode may be changed to be ERROR or higher in the future depending
582 on the results of testing and further review.
583 See "$?" for a description of the encoding of the Unix value to
585 produce a native VMS status containing it.
586 dump
588 Rather than causing Perl to abort and dump core, the "dump"
589 operator invokes the VMS debugger. If you continue to execute the
590 Perl program under the debugger, control will be transferred to the
591 label specified as the argument to "dump", or, if no label was
592 specified, back to the beginning of the program. All other state
593 of the program (e.g. values of variables, open file handles) are
594 not affected by calling "dump".
595 exec LIST
597 A call to "exec" will cause Perl to exit, and to invoke the command
598 given as an argument to "exec" via "lib$do_command". If the
599 argument begins with '@' or '$' (other than as part of a filespec),
600 then it is executed as a DCL command. Otherwise, the first token
601 on the command line is treated as the filespec of an image to run,
602 and an attempt is made to invoke it (using .Exe and the process
603 defaults to expand the filespec) and pass the rest of "exec"'s
604 argument to it as parameters. If the token has no file type, and
605 matches a file with null type, then an attempt is made to determine
606 whether the file is an executable image which should be invoked
607 using "MCR" or a text file which should be passed to DCL as a
608 command procedure.
609 fork
611 While in principle the "fork" operator could be implemented via
612 (and with the same rather severe limitations as) the CRTL "vfork()"
613 routine, and while some internal support to do just that is in
614 place, the implementation has never been completed, making "fork"
615 currently unavailable. A true kernel "fork()" is expected in a
616 future version of VMS, and the pseudo-fork based on interpreter
617 threads may be available in a future version of Perl on VMS (see
618 perlfork). In the meantime, use "system", backticks, or piped
619 filehandles to create subprocesses.
620 getpwent
622 getpwnam
623 getpwuid
624 These operators obtain the information described in perlfunc, if
625 you have the privileges necessary to retrieve the named user's UAF
626 information via "sys$getuai". If not, then only the $name, $uid,
627 and $gid items are returned. The $dir item contains the login
628 directory in VMS syntax, while the $comment item contains the login
629 directory in Unix syntax. The $gcos item contains the owner field
630 from the UAF record. The $quota item is not used.
631 gmtime
633 The "gmtime" operator will function properly if you have a working
634 CRTL "gmtime()" routine, or if the logical name
635 SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds which
636 must be added to UTC to yield local time. (This logical name is
637 defined automatically if you are running a version of VMS with
638 built-in UTC support.) If neither of these cases is true, a
639 warning message is printed, and "undef" is returned.
640 kill
642 In most cases, "kill" is implemented via the undocumented system
643 service $SIGPRC, which has the same calling sequence as $FORCEX,
644 but throws an exception in the target process rather than forcing
645 it to call $EXIT. Generally speaking, "kill" follows the behavior
646 of the CRTL's "kill()" function, but unlike that function can be
647 called from within a signal handler. Also, unlike the "kill" in
648 some versions of the CRTL, Perl's "kill" checks the validity of the
649 signal passed in and returns an error rather than attempting to
650 send an unrecognized signal.
651 Also, negative signal values don't do anything special under VMS;
653 they're just converted to the corresponding positive value.
654 qx//
656 See the entry on "backticks" above.
657 select (system call)
659 If Perl was not built with socket support, the system call version
660 of "select" is not available at all. If socket support is present,
661 then the system call version of "select" functions only for file
662 descriptors attached to sockets. It will not provide information
663 about regular files or pipes, since the CRTL "select()" routine
664 does not provide this functionality.
665 stat EXPR
667 Since VMS keeps track of files according to a different scheme than
668 Unix, it's not really possible to represent the file's ID in the
669 "st_dev" and "st_ino" fields of a "struct stat". Perl tries its
670 best, though, and the values it uses are pretty unlikely to be the
671 same for two different files. We can't guarantee this, though, so
672 caveat scriptor.
673 system LIST
675 The "system" operator creates a subprocess, and passes its
676 arguments to the subprocess for execution as a DCL command. Since
677 the subprocess is created directly via "lib$spawn()", any valid DCL
678 command string may be specified. If the string begins with '@', it
679 is treated as a DCL command unconditionally. Otherwise, if the
680 first token contains a character used as a delimiter in file
681 specification (e.g. ":" or "]"), an attempt is made to expand it
682 using a default type of .Exe and the process defaults, and if
683 successful, the resulting file is invoked via "MCR". This allows
684 you to invoke an image directly simply by passing the file
685 specification to "system", a common Unixish idiom. If the token
686 has no file type, and matches a file with null type, then an
687 attempt is made to determine whether the file is an executable
688 image which should be invoked using "MCR" or a text file which
689 should be passed to DCL as a command procedure.
690 If LIST consists of the empty string, "system" spawns an
692 interactive DCL subprocess, in the same fashion as typing SPAWN at
693 the DCL prompt.
694 Perl waits for the subprocess to complete before continuing
696 execution in the current process. As described in perlfunc, the
697 return value of "system" is a fake "status" which follows POSIX
698 semantics unless the pragma "use vmsish 'status'" is in effect; see
699 the description of $? in this document for more detail.
700 time
702 The value returned by "time" is the offset in seconds from
703 01-JAN-1970 00:00:00 (just like the CRTL's times() routine), in
704 order to make life easier for code coming in from the POSIX/Unix
705 world.
706 times
708 The array returned by the "times" operator is divided up according
709 to the same rules the CRTL "times()" routine. Therefore, the
710 "system time" elements will always be 0, since there is no
711 difference between "user time" and "system" time under VMS, and the
712 time accumulated by a subprocess may or may not appear separately
713 in the "child time" field, depending on whether "times()" keeps
714 track of subprocesses separately. Note especially that the VAXCRTL
715 (at least) keeps track only of subprocesses spawned using "fork()"
716 and "exec()"; it will not accumulate the times of subprocesses
717 spawned via pipes, "system()", or backticks.
718 unlink LIST
720 "unlink" will delete the highest version of a file only; in order
721 to delete all versions, you need to say
722 1 while unlink LIST;
724 You may need to make this change to scripts written for a Unix
726 system which expect that after a call to "unlink", no files with
727 the names passed to "unlink" will exist. (Note: This can be
728 changed at compile time; if you "use Config" and
729 $Config{'d_unlink_all_versions'} is "define", then "unlink" will
730 delete all versions of a file on the first call.)
731 "unlink" will delete a file if at all possible, even if it requires
733 changing file protection (though it won't try to change the
734 protection of the parent directory). You can tell whether you've
735 got explicit delete access to a file by using the
736 "VMS::Filespec::candelete" operator. For instance, in order to
737 delete only files to which you have delete access, you could say
738 something like
739 sub safe_unlink {
741 my($file,$num);
742 foreach $file (@_) {
743 next unless VMS::Filespec::candelete($file);
744 $num += unlink $file;
745 }
746 $num;
747 }
748 (or you could just use "VMS::Stdio::remove", if you've installed
750 the VMS::Stdio extension distributed with Perl). If "unlink" has to
751 change the file protection to delete the file, and you interrupt it
752 in midstream, the file may be left intact, but with a changed ACL
753 allowing you delete access.
754 This behavior of "unlink" is to be compatible with POSIX behavior
756 and not traditional VMS behavior.
757 utime LIST
759 This operator changes only the modification time of the file (VMS
760 revision date) on ODS-2 volumes and ODS-5 volumes without access
761 dates enabled. On ODS-5 volumes with access dates enabled, the true
762 access time is modified.
763 waitpid PID,FLAGS
765 If PID is a subprocess started by a piped "open()" (see open),
766 "waitpid" will wait for that subprocess, and return its final
767 status value in $?. If PID is a subprocess created in some other
768 way (e.g. SPAWNed before Perl was invoked), "waitpid" will simply
769 check once per second whether the process has completed, and return
770 when it has. (If PID specifies a process that isn't a subprocess
771 of the current process, and you invoked Perl with the "-w" switch,
772 a warning will be issued.)
773 Returns PID on success, -1 on error. The FLAGS argument is ignored
775 in all cases.
776
778 The following VMS-specific information applies to the indicated
779 "special" Perl variables, in addition to the general information in
780 perlvar. Where there is a conflict, this information takes precedence.
781 %ENV
783 The operation of the %ENV array depends on the translation of the
784 logical name PERL_ENV_TABLES. If defined, it should be a search
785 list, each element of which specifies a location for %ENV elements.
786 If you tell Perl to read or set the element "$ENV{"name"}", then
787 Perl uses the translations of PERL_ENV_TABLES as follows:
788 CRTL_ENV
790 This string tells Perl to consult the CRTL's internal "environ"
791 array of key-value pairs, using name as the key. In most
792 cases, this contains only a few keys, but if Perl was invoked
793 via the C "exec[lv]e()" function, as is the case for some
794 embedded Perl applications or when running under a shell such
795 as GNV bash, the "environ" array may have been populated by the
796 calling program.
797 CLISYM_[LOCAL]
799 A string beginning with "CLISYM_"tells Perl to consult the
800 CLI's symbol tables, using name as the name of the symbol.
801 When reading an element of %ENV, the local symbol table is
802 scanned first, followed by the global symbol table.. The
803 characters following "CLISYM_" are significant when an element
804 of %ENV is set or deleted: if the complete string is
805 "CLISYM_LOCAL", the change is made in the local symbol table;
806 otherwise the global symbol table is changed.
807 Any other string
809 If an element of PERL_ENV_TABLES translates to any other
810 string, that string is used as the name of a logical name
811 table, which is consulted using name as the logical name. The
812 normal search order of access modes is used.
813 PERL_ENV_TABLES is translated once when Perl starts up; any changes
815 you make while Perl is running do not affect the behavior of %ENV.
816 If PERL_ENV_TABLES is not defined, then Perl defaults to consulting
817 first the logical name tables specified by LNM$FILE_DEV, and then
818 the CRTL "environ" array. This default order is reversed when the
819 logical name GNV$UNIX_SHELL is defined, such as when running under
820 GNV bash.
821 For operations on %ENV entries based on logical names or DCL
823 symbols, the key string is treated as if it were entirely
824 uppercase, regardless of the case actually specified in the Perl
825 expression. Entries in %ENV based on the CRTL's environ array
826 preserve the case of the key string when stored, and lookups are
827 case sensitive.
828 When an element of %ENV is read, the locations to which
830 PERL_ENV_TABLES points are checked in order, and the value obtained
831 from the first successful lookup is returned. If the name of the
832 %ENV element contains a semi-colon, it and any characters after it
833 are removed. These are ignored when the CRTL "environ" array or a
834 CLI symbol table is consulted. However, the name is looked up in a
835 logical name table, the suffix after the semi-colon is treated as
836 the translation index to be used for the lookup. This lets you
837 look up successive values for search list logical names. For
838 instance, if you say
839 $ Define STORY once,upon,a,time,there,was
841 $ perl -e "for ($i = 0; $i <= 6; $i++) " -
842 _$ -e "{ print $ENV{'story;'.$i},' '}"
843 Perl will print "ONCE UPON A TIME THERE WAS", assuming, of course,
845 that PERL_ENV_TABLES is set up so that the logical name "story" is
846 found, rather than a CLI symbol or CRTL "environ" element with the
847 same name.
848 When an element of %ENV is set to a defined string, the
850 corresponding definition is made in the location to which the first
851 translation of PERL_ENV_TABLES points. If this causes a logical
852 name to be created, it is defined in supervisor mode. (The same is
853 done if an existing logical name was defined in executive or kernel
854 mode; an existing user or supervisor mode logical name is reset to
855 the new value.) If the value is an empty string, the logical
856 name's translation is defined as a single "NUL" (ASCII "\0")
857 character, since a logical name cannot translate to a zero-length
858 string. (This restriction does not apply to CLI symbols or CRTL
859 "environ" values; they are set to the empty string.)
860 When an element of %ENV is set to "undef", the element is looked up
862 as if it were being read, and if it is found, it is deleted. (An
863 item "deleted" from the CRTL "environ" array is set to the empty
864 string.) Using "delete" to remove an element from %ENV has a
865 similar effect, but after the element is deleted, another attempt
866 is made to look up the element, so an inner-mode logical name or a
867 name in another location will replace the logical name just
868 deleted. In either case, only the first value found searching
869 PERL_ENV_TABLES is altered. It is not possible at present to
870 define a search list logical name via %ENV.
871 The element $ENV{DEFAULT} is special: when read, it returns Perl's
873 current default device and directory, and when set, it resets them,
874 regardless of the definition of PERL_ENV_TABLES. It cannot be
875 cleared or deleted; attempts to do so are silently ignored.
876 Note that if you want to pass on any elements of the C-local
878 environ array to a subprocess which isn't started by fork/exec, or
879 isn't running a C program, you can "promote" them to logical names
880 in the current process, which will then be inherited by all
881 subprocesses, by saying
882 foreach my $key (qw[C-local keys you want promoted]) {
884 my $temp = $ENV{$key}; # read from C-local array
885 $ENV{$key} = $temp; # and define as logical name
886 }
887 (You can't just say $ENV{$key} = $ENV{$key}, since the Perl
889 optimizer is smart enough to elide the expression.)
890 Don't try to clear %ENV by saying "%ENV = ();", it will throw a
892 fatal error. This is equivalent to doing the following from DCL:
893 DELETE/LOGICAL *
895 You can imagine how bad things would be if, for example, the
897 SYS$MANAGER or SYS$SYSTEM logical names were deleted.
898 At present, the first time you iterate over %ENV using "keys", or
900 "values", you will incur a time penalty as all logical names are
901 read, in order to fully populate %ENV. Subsequent iterations will
902 not reread logical names, so they won't be as slow, but they also
903 won't reflect any changes to logical name tables caused by other
904 programs.
905 You do need to be careful with the logical names representing
907 process-permanent files, such as "SYS$INPUT" and "SYS$OUTPUT". The
908 translations for these logical names are prepended with a two-byte
909 binary value (0x1B 0x00) that needs to be stripped off if you want
910 to use it. (In previous versions of Perl it wasn't possible to get
911 the values of these logical names, as the null byte acted as an
912 end-of-string marker)
913 $! The string value of $! is that returned by the CRTL's strerror()
915 function, so it will include the VMS message for VMS-specific
916 errors. The numeric value of $! is the value of "errno", except if
917 errno is EVMSERR, in which case $! contains the value of
918 vaxc$errno. Setting $! always sets errno to the value specified.
919 If this value is EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-
920 NOMSG), so that the string value of $! won't reflect the VMS error
921 message from before $! was set.
922 $^E This variable provides direct access to VMS status values in
924 vaxc$errno, which are often more specific than the generic Unix-
925 style error messages in $!. Its numeric value is the value of
926 vaxc$errno, and its string value is the corresponding VMS message
927 string, as retrieved by sys$getmsg(). Setting $^E sets vaxc$errno
928 to the value specified.
929 While Perl attempts to keep the vaxc$errno value to be current, if
931 errno is not EVMSERR, it may not be from the current operation.
932 $? The "status value" returned in $? is synthesized from the actual
934 exit status of the subprocess in a way that approximates POSIX
935 wait(5) semantics, in order to allow Perl programs to portably test
936 for successful completion of subprocesses. The low order 8 bits of
937 $? are always 0 under VMS, since the termination status of a
938 process may or may not have been generated by an exception.
939 The next 8 bits contain the termination status of the program.
941 If the child process follows the convention of C programs compiled
943 with the _POSIX_EXIT macro set, the status value will contain the
944 actual value of 0 to 255 returned by that program on a normal exit.
945 With the _POSIX_EXIT macro set, the Unix exit value of zero is
947 represented as a VMS native status of 1, and the Unix values from 2
948 to 255 are encoded by the equation:
949 VMS_status = 0x35a000 + (unix_value * 8) + 1.
951 And in the special case of Unix value 1 the encoding is:
953 VMS_status = 0x35a000 + 8 + 2 + 0x10000000.
955 For other termination statuses, the severity portion of the
957 subprocess's exit status is used: if the severity was success or
958 informational, these bits are all 0; if the severity was warning,
959 they contain a value of 1; if the severity was error or fatal
960 error, they contain the actual severity bits, which turns out to be
961 a value of 2 for error and 4 for severe_error. Fatal is another
962 term for the severe_error status.
963 As a result, $? will always be zero if the subprocess's exit status
965 indicated successful completion, and non-zero if a warning or error
966 occurred or a program compliant with encoding _POSIX_EXIT values
967 was run and set a status.
968 How can you tell the difference between a non-zero status that is
970 the result of a VMS native error status or an encoded Unix status?
971 You can not unless you look at the ${^CHILD_ERROR_NATIVE} value.
972 The ${^CHILD_ERROR_NATIVE} value returns the actual VMS status
973 value and check the severity bits. If the severity bits are equal
974 to 1, then if the numeric value for $? is between 2 and 255 or 0,
975 then $? accurately reflects a value passed back from a Unix
976 application. If $? is 1, and the severity bits indicate a VMS
977 error (2), then $? is from a Unix application exit value.
978 In practice, Perl scripts that call programs that return
980 _POSIX_EXIT type status values will be expecting those values, and
981 programs that call traditional VMS programs will either be
982 expecting the previous behavior or just checking for a non-zero
983 status.
984 And success is always the value 0 in all behaviors.
986 When the actual VMS termination status of the child is an error,
988 internally the $! value will be set to the closest Unix errno value
989 to that error so that Perl scripts that test for error messages
990 will see the expected Unix style error message instead of a VMS
991 message.
992 Conversely, when setting $? in an END block, an attempt is made to
994 convert the POSIX value into a native status intelligible to the
995 operating system upon exiting Perl. What this boils down to is
996 that setting $? to zero results in the generic success value
997 SS$_NORMAL, and setting $? to a non-zero value results in the
998 generic failure status SS$_ABORT. See also "exit" in perlport.
999 With the "PERL_VMS_POSIX_EXIT" logical name defined as "ENABLE",
1001 setting $? will cause the new value to be encoded into $^E so that
1002 either the original parent or child exit status values
1003 0 to 255 can be automatically recovered by C programs expecting
1004 _POSIX_EXIT behavior. If both a parent and a child exit value are
1005 non-zero, then it will be assumed that this is actually a VMS
1006 native status value to be passed through. The special value of
1007 0xFFFF is almost a NOOP as it will cause the current native VMS
1008 status in the C library to become the current native Perl VMS
1009 status, and is handled this way as it is known to not be a valid
1010 native VMS status value. It is recommend that only values in the
1011 range of normal Unix parent or child status numbers, 0 to 255 are
1012 used.
1013 The pragma "use vmsish 'status'" makes $? reflect the actual VMS
1015 exit status instead of the default emulation of POSIX status
1016 described above. This pragma also disables the conversion of non-
1017 zero values to SS$_ABORT when setting $? in an END block (but zero
1018 will still be converted to SS$_NORMAL).
1019 Do not use the pragma "use vmsish 'status'" with
1021 "PERL_VMS_POSIX_EXIT" enabled, as they are at times requesting
1022 conflicting actions and the consequence of ignoring this advice
1023 will be undefined to allow future improvements in the POSIX exit
1024 handling.
1025 In general, with "PERL_VMS_POSIX_EXIT" enabled, more detailed
1027 information will be available in the exit status for DCL scripts or
1028 other native VMS tools, and will give the expected information for
1029 Posix programs. It has not been made the default in order to
1030 preserve backward compatibility.
1031 N.B. Setting "DECC$FILENAME_UNIX_REPORT" implicitly enables
1033 "PERL_VMS_POSIX_EXIT".
1034 $| Setting $| for an I/O stream causes data to be flushed all the way
1036 to disk on each write (i.e. not just to the underlying RMS buffers
1037 for a file). In other words, it's equivalent to calling fflush()
1038 and fsync() from C.
1039
1041 SDBM_File
1042 SDBM_File works properly on VMS. It has, however, one minor difference.
1043 The database directory file created has a .sdbm_dir extension rather
1044 than a .dir extension. .dir files are VMS filesystem directory files,
1045 and using them for other purposes could cause unacceptable problems.
1046
1048 Please see the git repository for revision history.
1049
1051 Charles Bailey bailey@cor.newman.upenn.edu Craig Berry
1052 craigberry@mac.com Dan Sugalski dan@sidhe.org John Malmberg
1053 wb8tyw@qsl.net
1054perl v5.32.1 2021-03-31 PERLVMS(1)