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1=head1 NAME
2
3perlvms - VMS-specific documentation for Perl
4
5=head1 DESCRIPTION
a0d0e21e 6
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7Gathered below are notes describing details of Perl 5's
8behavior on VMS. They are a supplement to the regular Perl 5
9documentation, so we have focussed on the ways in which Perl
105 functions differently under VMS than it does under Unix,
11and on the interactions between Perl and the rest of the
a0d0e21e 12operating system. We haven't tried to duplicate complete
748a9306 13descriptions of Perl features from the main Perl
a0d0e21e 14documentation, which can be found in the F<[.pod]>
748a9306 15subdirectory of the Perl distribution.
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16
17We hope these notes will save you from confusion and lost
748a9306 18sleep when writing Perl scripts on VMS. If you find we've
a0d0e21e 19missed something you think should appear here, please don't
9bc98430 20hesitate to drop a line to vmsperl@perl.org.
a0d0e21e 21
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22=head1 Installation
23
24Directions for building and installing Perl 5 can be found in
25the file F<README.vms> in the main source directory of the
26Perl distribution..
27
e518068a 28=head1 Organization of Perl Images
748a9306 29
e518068a 30=head2 Core Images
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31
32During the installation process, three Perl images are produced.
33F<Miniperl.Exe> is an executable image which contains all of
34the basic functionality of Perl, but cannot take advantage of
35Perl extensions. It is used to generate several files needed
36to build the complete Perl and various extensions. Once you've
37finished installing Perl, you can delete this image.
38
39Most of the complete Perl resides in the shareable image
40F<PerlShr.Exe>, which provides a core to which the Perl executable
41image and all Perl extensions are linked. You should place this
42image in F<Sys$Share>, or define the logical name F<PerlShr> to
43translate to the full file specification of this image. It should
44be world readable. (Remember that if a user has execute only access
45to F<PerlShr>, VMS will treat it as if it were a privileged shareable
46image, and will therefore require all downstream shareable images to be
47INSTALLed, etc.)
48
49
50Finally, F<Perl.Exe> is an executable image containing the main
51entry point for Perl, as well as some initialization code. It
52should be placed in a public directory, and made world executable.
53In order to run Perl with command line arguments, you should
54define a foreign command to invoke this image.
55
56=head2 Perl Extensions
57
58Perl extensions are packages which provide both XS and Perl code
59to add new functionality to perl. (XS is a meta-language which
60simplifies writing C code which interacts with Perl, see
2ceaccd7 61L<perlxs> for more details.) The Perl code for an
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62extension is treated like any other library module - it's
63made available in your script through the appropriate
64C<use> or C<require> statement, and usually defines a Perl
65package containing the extension.
66
67The portion of the extension provided by the XS code may be
68connected to the rest of Perl in either of two ways. In the
69B<static> configuration, the object code for the extension is
70linked directly into F<PerlShr.Exe>, and is initialized whenever
71Perl is invoked. In the B<dynamic> configuration, the extension's
72machine code is placed into a separate shareable image, which is
73mapped by Perl's DynaLoader when the extension is C<use>d or
74C<require>d in your script. This allows you to maintain the
75extension as a separate entity, at the cost of keeping track of the
76additional shareable image. Most extensions can be set up as either
77static or dynamic.
78
79The source code for an extension usually resides in its own
80directory. At least three files are generally provided:
81I<Extshortname>F<.xs> (where I<Extshortname> is the portion of
82the extension's name following the last C<::>), containing
83the XS code, I<Extshortname>F<.pm>, the Perl library module
84for the extension, and F<Makefile.PL>, a Perl script which uses
85the C<MakeMaker> library modules supplied with Perl to generate
86a F<Descrip.MMS> file for the extension.
87
e518068a 88=head2 Installing static extensions
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89
90Since static extensions are incorporated directly into
91F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a
92new extension. You should edit the main F<Descrip.MMS> or F<Makefile>
93you use to build Perl, adding the extension's name to the C<ext>
94macro, and the extension's object file to the C<extobj> macro.
95You'll also need to build the extension's object file, either
96by adding dependencies to the main F<Descrip.MMS>, or using a
97separate F<Descrip.MMS> for the extension. Then, rebuild
98F<PerlShr.Exe> to incorporate the new code.
99
100Finally, you'll need to copy the extension's Perl library
101module to the F<[.>I<Extname>F<]> subdirectory under one
102of the directories in C<@INC>, where I<Extname> is the name
103of the extension, with all C<::> replaced by C<.> (e.g.
104the library module for extension Foo::Bar would be copied
105to a F<[.Foo.Bar]> subdirectory).
106
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107=head2 Installing dynamic extensions
108
109In general, the distributed kit for a Perl extension includes
110a file named Makefile.PL, which is a Perl program which is used
111to create a F<Descrip.MMS> file which can be used to build and
112install the files required by the extension. The kit should be
c07a80fd 113unpacked into a directory tree B<not> under the main Perl source
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114directory, and the procedure for building the extension is simply
115
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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
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121I<N.B.> The procedure by which extensions are built and
122tested creates several levels (at least 4) under the
123directory in which the extension's source files live.
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124For this reason if you are runnning a version of VMS prior
125to V7.1 you shouldn't nest the source directory
126too deeply in your directory structure lest you exceed RMS'
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127maximum of 8 levels of subdirectory in a filespec. (You
128can use rooted logical names to get another 8 levels of
129nesting, if you can't place the files near the top of
130the physical directory structure.)
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131
132VMS support for this process in the current release of Perl
133is sufficient to handle most extensions. However, it does
134not yet recognize extra libraries required to build shareable
135images which are part of an extension, so these must be added
136to the linker options file for the extension by hand. For
137instance, if the F<PGPLOT> extension to Perl requires the
138F<PGPLOTSHR.EXE> shareable image in order to properly link
139the Perl extension, then the line C<PGPLOTSHR/Share> must
140be added to the linker options file F<PGPLOT.Opt> produced
141during the build process for the Perl extension.
142
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143By default, the shareable image for an extension is placed in
144the F<[.lib.site_perl.auto>I<Arch>.I<Extname>F<]> directory of the
e518068a 145installed Perl directory tree (where I<Arch> is F<VMS_VAX> or
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146F<VMS_AXP>, and I<Extname> is the name of the extension, with
147each C<::> translated to C<.>). (See the MakeMaker documentation
148for more details on installation options for extensions.)
4e592037 149However, it can be manually placed in any of several locations:
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150
151=over 4
152
153=item *
154
155the F<[.Lib.Auto.>I<Arch>I<$PVers>I<Extname>F<]> subdirectory
156of one of the directories in C<@INC> (where I<PVers>
157is the version of Perl you're using, as supplied in C<$]>,
158with '.' converted to '_'), or
159
160=item *
161
162one of the directories in C<@INC>, or
163
164=item *
165
166a directory which the extensions Perl library module
167passes to the DynaLoader when asking it to map
168the shareable image, or
169
170=item *
171
172F<Sys$Share> or F<Sys$Library>.
173
174=back
175
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176If the shareable image isn't in any of these places, you'll need
177to define a logical name I<Extshortname>, where I<Extshortname>
178is the portion of the extension's name after the last C<::>, which
179translates to the full file specification of the shareable image.
180
4e592037 181=head1 File specifications
748a9306 182
4e592037 183=head2 Syntax
a0d0e21e 184
748a9306 185We have tried to make Perl aware of both VMS-style and Unix-
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186style file specifications wherever possible. You may use
187either style, or both, on the command line and in scripts,
39aca757 188but you may not combine the two styles within a single file
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189specification. VMS Perl interprets Unix pathnames in much
190the same way as the CRTL (I<e.g.> the first component of
191an absolute path is read as the device name for the
192VMS file specification). There are a set of functions
193provided in the C<VMS::Filespec> package for explicit
194interconversion between VMS and Unix syntax; its
195documentation provides more details.
196
197Filenames are, of course, still case-insensitive. For
198consistency, most Perl routines return filespecs using
199lower case letters only, regardless of the case used in
200the arguments passed to them. (This is true only when
201running under VMS; Perl respects the case-sensitivity
202of OSs like Unix.)
a0d0e21e 203
748a9306 204We've tried to minimize the dependence of Perl library
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205modules on Unix syntax, but you may find that some of these,
206as well as some scripts written for Unix systems, will
207require that you use Unix syntax, since they will assume that
4e592037 208'/' is the directory separator, I<etc.> If you find instances
748a9306 209of this in the Perl distribution itself, please let us know,
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210so we can try to work around them.
211
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212=head2 Wildcard expansion
213
214File specifications containing wildcards are allowed both on
07698885 215the command line and within Perl globs (e.g. C<E<lt>*.cE<gt>>). If
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216the wildcard filespec uses VMS syntax, the resultant
217filespecs will follow VMS syntax; if a Unix-style filespec is
218passed in, Unix-style filespecs will be returned.
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219Similar to the behavior of wildcard globbing for a Unix shell,
220one can escape command line wildcards with double quotation
221marks C<"> around a perl program command line argument. However,
222owing to the stripping of C<"> characters carried out by the C
223handling of argv you will need to escape a construct such as
224this one (in a directory containing the files F<PERL.C>, F<PERL.EXE>,
225F<PERL.H>, and F<PERL.OBJ>):
226
227 $ perl -e "print join(' ',@ARGV)" perl.*
228 perl.c perl.exe perl.h perl.obj
229
230in the following triple quoted manner:
231
232 $ perl -e "print join(' ',@ARGV)" """perl.*"""
233 perl.*
4e592037 234
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235In both the case of unquoted command line arguments or in calls
236to C<glob()> VMS wildcard expansion is performed. (csh-style
aa779de1 237wildcard expansion is available if you use C<File::Glob::glob>.)
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238If the wildcard filespec contains a device or directory
239specification, then the resultant filespecs will also contain
240a device and directory; otherwise, device and directory
241information are removed. VMS-style resultant filespecs will
242contain a full device and directory, while Unix-style
243resultant filespecs will contain only as much of a directory
244path as was present in the input filespec. For example, if
245your default directory is Perl_Root:[000000], the expansion
246of C<[.t]*.*> will yield filespecs like
247"perl_root:[t]base.dir", while the expansion of C<t/*/*> will
248yield filespecs like "t/base.dir". (This is done to match
249the behavior of glob expansion performed by Unix shells.)
250
251Similarly, the resultant filespec will contain the file version
252only if one was present in the input filespec.
253
254=head2 Pipes
255
256Input and output pipes to Perl filehandles are supported; the
257"file name" is passed to lib$spawn() for asynchronous
258execution. You should be careful to close any pipes you have
259opened in a Perl script, lest you leave any "orphaned"
260subprocesses around when Perl exits.
261
262You may also use backticks to invoke a DCL subprocess, whose
263output is used as the return value of the expression. The
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264string between the backticks is handled as if it were the
265argument to the C<system> operator (see below). In this case,
266Perl will wait for the subprocess to complete before continuing.
4e592037 267
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268The mailbox (MBX) that perl can create to communicate with a pipe
269defaults to a buffer size of 512. The default buffer size is
1506e54c 270adjustable via the logical name PERL_MBX_SIZE provided that the
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271value falls between 128 and the SYSGEN parameter MAXBUF inclusive.
272For example, to double the MBX size from the default within
1506e54c 273a Perl program, use C<$ENV{'PERL_MBX_SIZE'} = 1024;> and then
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274open and use pipe constructs. An alternative would be to issue
275the command:
276
277 $ Define PERL_MBX_SIZE 1024
278
279before running your wide record pipe program. A larger value may
280improve performance at the expense of the BYTLM UAF quota.
281
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282=head1 PERL5LIB and PERLLIB
283
39aca757 284The PERL5LIB and PERLLIB logical names work as documented in L<perl>,
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285except that the element separator is '|' instead of ':'. The
286directory specifications may use either VMS or Unix syntax.
287
288=head1 Command line
289
290=head2 I/O redirection and backgrounding
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291
292Perl for VMS supports redirection of input and output on the
293command line, using a subset of Bourne shell syntax:
55497cff 294
773da73d 295=over 4
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296
297=item *
298
299C<E<lt>file> reads stdin from C<file>,
300
301=item *
302
303C<E<gt>file> writes stdout to C<file>,
304
305=item *
306
307C<E<gt>E<gt>file> appends stdout to C<file>,
308
309=item *
310
2fde0ff0 311C<2E<gt>file> writes stderr to C<file>,
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312
313=item *
314
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315C<2E<gt>E<gt>file> appends stderr to C<file>, and
316
317=item *
318
319C<< 2>&1 >> redirects stderr to stdout.
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320
321=back
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322
323In addition, output may be piped to a subprocess, using the
324character '|'. Anything after this character on the command
325line is passed to a subprocess for execution; the subprocess
748a9306 326takes the output of Perl as its input.
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327
328Finally, if the command line ends with '&', the entire
329command is run in the background as an asynchronous
330subprocess.
331
4e592037 332=head2 Command line switches
a0d0e21e 333
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334The following command line switches behave differently under
335VMS than described in L<perlrun>. Note also that in order
336to pass uppercase switches to Perl, you need to enclose
337them in double-quotes on the command line, since the CRTL
338downcases all unquoted strings.
a0d0e21e 339
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340=over 4
341
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342=item -i
343
344If the C<-i> switch is present but no extension for a backup
345copy is given, then inplace editing creates a new version of
346a file; the existing copy is not deleted. (Note that if
347an extension is given, an existing file is renamed to the backup
348file, as is the case under other operating systems, so it does
349not remain as a previous version under the original filename.)
350
4e592037 351=item -S
a0d0e21e 352
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353If the C<"-S"> or C<-"S"> switch is present I<and> the script
354name does not contain a directory, then Perl translates the
355logical name DCL$PATH as a searchlist, using each translation
356as a directory in which to look for the script. In addition,
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357if no file type is specified, Perl looks in each directory
358for a file matching the name specified, with a blank type,
359a type of F<.pl>, and a type of F<.com>, in that order.
a0d0e21e 360
4e592037 361=item -u
748a9306 362
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363The C<-u> switch causes the VMS debugger to be invoked
364after the Perl program is compiled, but before it has
365run. It does not create a core dump file.
748a9306 366
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367=back
368
748a9306 369=head1 Perl functions
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370
371As of the time this document was last revised, the following
748a9306 372Perl functions were implemented in the VMS port of Perl
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373(functions marked with * are discussed in more detail below):
374
4fdae800 375 file tests*, abs, alarm, atan, backticks*, binmode*, bless,
a0d0e21e 376 caller, chdir, chmod, chown, chomp, chop, chr,
c07a80fd 377 close, closedir, cos, crypt*, defined, delete,
4e592037 378 die, do, dump*, each, endpwent, eof, eval, exec*,
41cbbefa 379 exists, exit, exp, fileno, getc, getlogin, getppid,
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380 getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto,
381 grep, hex, import, index, int, join, keys, kill*,
382 last, lc, lcfirst, length, local, localtime, log, m//,
383 map, mkdir, my, next, no, oct, open, opendir, ord, pack,
c07a80fd 384 pipe, pop, pos, print, printf, push, q//, qq//, qw//,
4fdae800 385 qx//*, quotemeta, rand, read, readdir, redo, ref, rename,
a0d0e21e 386 require, reset, return, reverse, rewinddir, rindex,
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387 rmdir, s///, scalar, seek, seekdir, select(internal),
388 select (system call)*, setpwent, shift, sin, sleep,
389 sort, splice, split, sprintf, sqrt, srand, stat,
390 study, substr, sysread, system*, syswrite, tell,
391 telldir, tie, time, times*, tr///, uc, ucfirst, umask,
392 undef, unlink*, unpack, untie, unshift, use, utime*,
393 values, vec, wait, waitpid*, wantarray, warn, write, y///
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394
395The following functions were not implemented in the VMS port,
396and calling them produces a fatal error (usually) or
397undefined behavior (rarely, we hope):
398
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399 chroot, dbmclose, dbmopen, flock, fork*,
400 getpgrp, getpriority, getgrent, getgrgid,
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401 getgrnam, setgrent, endgrent, ioctl, link, lstat,
402 msgctl, msgget, msgsend, msgrcv, readlink, semctl,
403 semget, semop, setpgrp, setpriority, shmctl, shmget,
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404 shmread, shmwrite, socketpair, symlink, syscall
405
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406The following functions are available on Perls compiled with Dec C
4075.2 or greater and running VMS 7.0 or greater:
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408
409 truncate
a0d0e21e 410
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411The following functions are available on Perls built on VMS 7.2 or
412greater:
413
414 fcntl (without locking)
415
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416The following functions may or may not be implemented,
417depending on what type of socket support you've built into
748a9306 418your copy of Perl:
4e592037 419
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420 accept, bind, connect, getpeername,
421 gethostbyname, getnetbyname, getprotobyname,
422 getservbyname, gethostbyaddr, getnetbyaddr,
423 getprotobynumber, getservbyport, gethostent,
424 getnetent, getprotoent, getservent, sethostent,
425 setnetent, setprotoent, setservent, endhostent,
426 endnetent, endprotoent, endservent, getsockname,
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427 getsockopt, listen, recv, select(system call)*,
428 send, setsockopt, shutdown, socket
a0d0e21e 429
55497cff 430=over 4
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431
432=item File tests
433
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434The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>,
435C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as
436advertised. The return values for C<-r>, C<-w>, and C<-x>
437tell you whether you can actually access the file; this may
438not reflect the UIC-based file protections. Since real and
439effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>,
440and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>.
441Similarly, several other tests, including C<-A>, C<-g>, C<-k>,
442C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under
443VMS, and the values returned by these tests reflect whatever
444your CRTL C<stat()> routine does to the equivalent bits in the
445st_mode field. Finally, C<-d> returns true if passed a device
446specification without an explicit directory (e.g. C<DUA1:>), as
447well as if passed a directory.
448
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449Note: Some sites have reported problems when using the file-access
450tests (C<-r>, C<-w>, and C<-x>) on files accessed via DEC's DFS.
451Specifically, since DFS does not currently provide access to the
452extended file header of files on remote volumes, attempts to
453examine the ACL fail, and the file tests will return false,
454with C<$!> indicating that the file does not exist. You can
455use C<stat> on these files, since that checks UIC-based protection
456only, and then manually check the appropriate bits, as defined by
457your C compiler's F<stat.h>, in the mode value it returns, if you
458need an approximation of the file's protections.
459
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460=item backticks
461
462Backticks create a subprocess, and pass the enclosed string
463to it for execution as a DCL command. Since the subprocess is
464created directly via C<lib$spawn()>, any valid DCL command string
465may be specified.
466
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467=item binmode FILEHANDLE
468
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469The C<binmode> operator will attempt to insure that no translation
470of carriage control occurs on input from or output to this filehandle.
471Since this involves reopening the file and then restoring its
472file position indicator, if this function returns FALSE, the
473underlying filehandle may no longer point to an open file, or may
474point to a different position in the file than before C<binmode>
475was called.
476
477Note that C<binmode> is generally not necessary when using normal
478filehandles; it is provided so that you can control I/O to existing
479record-structured files when necessary. You can also use the
480C<vmsfopen> function in the VMS::Stdio extension to gain finer
481control of I/O to files and devices with different record structures.
a0d0e21e 482
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483=item crypt PLAINTEXT, USER
484
485The C<crypt> operator uses the C<sys$hash_password> system
486service to generate the hashed representation of PLAINTEXT.
487If USER is a valid username, the algorithm and salt values
488are taken from that user's UAF record. If it is not, then
489the preferred algorithm and a salt of 0 are used. The
490quadword encrypted value is returned as an 8-character string.
491
492The value returned by C<crypt> may be compared against
493the encrypted password from the UAF returned by the C<getpw*>
494functions, in order to authenticate users. If you're
495going to do this, remember that the encrypted password in
496the UAF was generated using uppercase username and
497password strings; you'll have to upcase the arguments to
498C<crypt> to insure that you'll get the proper value:
499
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500 sub validate_passwd {
501 my($user,$passwd) = @_;
502 my($pwdhash);
503 if ( !($pwdhash = (getpwnam($user))[1]) ||
504 $pwdhash ne crypt("\U$passwd","\U$name") ) {
505 intruder_alert($name);
506 }
507 return 1;
c07a80fd 508 }
c07a80fd 509
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510=item dump
511
512Rather than causing Perl to abort and dump core, the C<dump>
513operator invokes the VMS debugger. If you continue to
514execute the Perl program under the debugger, control will
515be transferred to the label specified as the argument to
516C<dump>, or, if no label was specified, back to the
517beginning of the program. All other state of the program
518(I<e.g.> values of variables, open file handles) are not
519affected by calling C<dump>.
520
748a9306 521=item exec LIST
a0d0e21e 522
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523A call to C<exec> will cause Perl to exit, and to invoke the command
524given as an argument to C<exec> via C<lib$do_command>. If the
525argument begins with '@' or '$' (other than as part of a filespec),
526then it is executed as a DCL command. Otherwise, the first token on
527the command line is treated as the filespec of an image to run, and
528an attempt is made to invoke it (using F<.Exe> and the process
529defaults to expand the filespec) and pass the rest of C<exec>'s
530argument to it as parameters. If the token has no file type, and
531matches a file with null type, then an attempt is made to determine
532whether the file is an executable image which should be invoked
533using C<MCR> or a text file which should be passed to DCL as a
534command procedure.
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535
536=item fork
537
41cbbefa
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538While in principle the C<fork> operator could be implemented via
539(and with the same rather severe limitations as) the CRTL C<vfork()>
540routine, and while some internal support to do just that is in
541place, the implementation has never been completed, making C<fork>
542currently unavailable. A true kernel C<fork()> is expected in a
543future version of VMS, and the pseudo-fork based on interpreter
544threads may be available in a future version of Perl on VMS (see
545L<perlfork>). In the meantime, use C<system>, backticks, or piped
546filehandles to create subprocesses.
748a9306
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547
548=item getpwent
c07a80fd 549
748a9306 550=item getpwnam
c07a80fd 551
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552=item getpwuid
553
554These operators obtain the information described in L<perlfunc>,
555if you have the privileges necessary to retrieve the named user's
556UAF information via C<sys$getuai>. If not, then only the C<$name>,
557C<$uid>, and C<$gid> items are returned. The C<$dir> item contains
558the login directory in VMS syntax, while the C<$comment> item
559contains the login directory in Unix syntax. The C<$gcos> item
560contains the owner field from the UAF record. The C<$quota>
561item is not used.
a0d0e21e 562
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563=item gmtime
564
565The C<gmtime> operator will function properly if you have a
566working CRTL C<gmtime()> routine, or if the logical name
567SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds
568which must be added to UTC to yield local time. (This logical
569name is defined automatically if you are running a version of
570VMS with built-in UTC support.) If neither of these cases is
571true, a warning message is printed, and C<undef> is returned.
572
573=item kill
574
39aca757 575In most cases, C<kill> is implemented via the CRTL's C<kill()>
e518068a
PP
576function, so it will behave according to that function's
577documentation. If you send a SIGKILL, however, the $DELPRC system
10a676f8 578service is called directly. This insures that the target
e518068a
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579process is actually deleted, if at all possible. (The CRTL's C<kill()>
580function is presently implemented via $FORCEX, which is ignored by
581supervisor-mode images like DCL.)
582
583Also, negative signal values don't do anything special under
584VMS; they're just converted to the corresponding positive value.
585
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586=item qx//
587
588See the entry on C<backticks> above.
589
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590=item select (system call)
591
592If Perl was not built with socket support, the system call
593version of C<select> is not available at all. If socket
594support is present, then the system call version of
595C<select> functions only for file descriptors attached
596to sockets. It will not provide information about regular
597files or pipes, since the CRTL C<select()> routine does not
598provide this functionality.
599
748a9306 600=item stat EXPR
a0d0e21e 601
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602Since VMS keeps track of files according to a different scheme
603than Unix, it's not really possible to represent the file's ID
604in the C<st_dev> and C<st_ino> fields of a C<struct stat>. Perl
605tries its best, though, and the values it uses are pretty unlikely
606to be the same for two different files. We can't guarantee this,
607though, so caveat scriptor.
608
609=item system LIST
610
611The C<system> operator creates a subprocess, and passes its
a0d0e21e 612arguments to the subprocess for execution as a DCL command.
e518068a 613Since the subprocess is created directly via C<lib$spawn()>, any
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614valid DCL command string may be specified. If the string begins with
615'@', it is treated as a DCL command unconditionally. Otherwise, if
616the first token contains a character used as a delimiter in file
617specification (e.g. C<:> or C<]>), an attempt is made to expand it
618using a default type of F<.Exe> and the process defaults, and if
619successful, the resulting file is invoked via C<MCR>. This allows you
620to invoke an image directly simply by passing the file specification
c93fa817
GS
621to C<system>, a common Unixish idiom. If the token has no file type,
622and matches a file with null type, then an attempt is made to
623determine whether the file is an executable image which should be
624invoked using C<MCR> or a text file which should be passed to DCL
625as a command procedure.
626
627If LIST consists of the empty string, C<system> spawns an
a2293a43 628interactive DCL subprocess, in the same fashion as typing
c93fa817
GS
629B<SPAWN> at the DCL prompt.
630
748a9306 631Perl waits for the subprocess to complete before continuing
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PP
632execution in the current process. As described in L<perlfunc>,
633the return value of C<system> is a fake "status" which follows
c6966fea 634POSIX semantics unless the pragma C<use vmsish 'status'> is in
1b0c4952
CB
635effect; see the description of C<$?> in this document for more
636detail.
a0d0e21e 637
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638=item time
639
640The value returned by C<time> is the offset in seconds from
64101-JAN-1970 00:00:00 (just like the CRTL's times() routine), in order
642to make life easier for code coming in from the POSIX/Unix world.
643
a0d0e21e
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644=item times
645
748a9306
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646The array returned by the C<times> operator is divided up
647according to the same rules the CRTL C<times()> routine.
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648Therefore, the "system time" elements will always be 0, since
649there is no difference between "user time" and "system" time
39aca757 650under VMS, and the time accumulated by a subprocess may or may
a0d0e21e 651not appear separately in the "child time" field, depending on
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652whether L<times> keeps track of subprocesses separately. Note
653especially that the VAXCRTL (at least) keeps track only of
654subprocesses spawned using L<fork> and L<exec>; it will not
a2293a43 655accumulate the times of subprocesses spawned via pipes, L<system>,
748a9306
LW
656or backticks.
657
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AD
658=item unlink LIST
659
660C<unlink> will delete the highest version of a file only; in
661order to delete all versions, you need to say
39aca757 662
35b2760a 663 1 while unlink LIST;
39aca757 664
16d20bd9
AD
665You may need to make this change to scripts written for a
666Unix system which expect that after a call to C<unlink>,
667no files with the names passed to C<unlink> will exist.
4633a7c4
LW
668(Note: This can be changed at compile time; if you
669C<use Config> and C<$Config{'d_unlink_all_versions'}> is
670C<define>, then C<unlink> will delete all versions of a
671file on the first call.)
16d20bd9
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672
673C<unlink> will delete a file if at all possible, even if it
674requires changing file protection (though it won't try to
675change the protection of the parent directory). You can tell
676whether you've got explicit delete access to a file by using the
677C<VMS::Filespec::candelete> operator. For instance, in order
678to delete only files to which you have delete access, you could
679say something like
4e592037 680
16d20bd9
AD
681 sub safe_unlink {
682 my($file,$num);
683 foreach $file (@_) {
684 next unless VMS::Filespec::candelete($file);
685 $num += unlink $file;
686 }
687 $num;
688 }
4e592037
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689
690(or you could just use C<VMS::Stdio::remove>, if you've installed
691the VMS::Stdio extension distributed with Perl). If C<unlink> has to
692change the file protection to delete the file, and you interrupt it
693in midstream, the file may be left intact, but with a changed ACL
694allowing you delete access.
16d20bd9 695
748a9306
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696=item utime LIST
697
698Since ODS-2, the VMS file structure for disk files, does not keep
699track of access times, this operator changes only the modification
700time of the file (VMS revision date).
701
702=item waitpid PID,FLAGS
703
39aca757 704If PID is a subprocess started by a piped C<open()> (see L<open>),
376ae1f1
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705C<waitpid> will wait for that subprocess, and return its final status
706value in C<$?>. If PID is a subprocess created in some other way (e.g.
707SPAWNed before Perl was invoked), C<waitpid> will simply check once per
708second whether the process has completed, and return when it has. (If
709PID specifies a process that isn't a subprocess of the current process,
710and you invoked Perl with the C<-w> switch, a warning will be issued.)
35b2760a
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711
712Returns PID on success, -1 on error. The FLAGS argument is ignored
713in all cases.
a0d0e21e 714
55497cff
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715=back
716
a5f75d66
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717=head1 Perl variables
718
55497cff
PP
719The following VMS-specific information applies to the indicated
720"special" Perl variables, in addition to the general information
a2293a43 721in L<perlvar>. Where there is a conflict, this information
55497cff
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722takes precedence.
723
724=over 4
725
a5f75d66
AD
726=item %ENV
727
f675dbe5
CB
728The operation of the C<%ENV> array depends on the translation
729of the logical name F<PERL_ENV_TABLES>. If defined, it should
730be a search list, each element of which specifies a location
731for C<%ENV> elements. If you tell Perl to read or set the
732element C<$ENV{>I<name>C<}>, then Perl uses the translations of
733F<PERL_ENV_TABLES> as follows:
734
735=over 4
736
737=item CRTL_ENV
738
739This string tells Perl to consult the CRTL's internal C<environ>
740array of key-value pairs, using I<name> as the key. In most cases,
741this contains only a few keys, but if Perl was invoked via the C
742C<exec[lv]e()> function, as is the case for CGI processing by some
743HTTP servers, then the C<environ> array may have been populated by
744the calling program.
745
746=item CLISYM_[LOCAL]
747
748A string beginning with C<CLISYM_>tells Perl to consult the CLI's
749symbol tables, using I<name> as the name of the symbol. When reading
750an element of C<%ENV>, the local symbol table is scanned first, followed
751by the global symbol table.. The characters following C<CLISYM_> are
752significant when an element of C<%ENV> is set or deleted: if the
753complete string is C<CLISYM_LOCAL>, the change is made in the local
39aca757 754symbol table; otherwise the global symbol table is changed.
f675dbe5
CB
755
756=item Any other string
757
758If an element of F<PERL_ENV_TABLES> translates to any other string,
759that string is used as the name of a logical name table, which is
760consulted using I<name> as the logical name. The normal search
761order of access modes is used.
762
763=back
764
765F<PERL_ENV_TABLES> is translated once when Perl starts up; any changes
766you make while Perl is running do not affect the behavior of C<%ENV>.
767If F<PERL_ENV_TABLES> is not defined, then Perl defaults to consulting
768first the logical name tables specified by F<LNM$FILE_DEV>, and then
769the CRTL C<environ> array.
770
771In all operations on %ENV, the key string is treated as if it
772were entirely uppercase, regardless of the case actually
773specified in the Perl expression.
774
775When an element of C<%ENV> is read, the locations to which
776F<PERL_ENV_TABLES> points are checked in order, and the value
777obtained from the first successful lookup is returned. If the
778name of the C<%ENV> element contains a semi-colon, it and
779any characters after it are removed. These are ignored when
780the CRTL C<environ> array or a CLI symbol table is consulted.
781However, the name is looked up in a logical name table, the
782suffix after the semi-colon is treated as the translation index
783to be used for the lookup. This lets you look up successive values
784for search list logical names. For instance, if you say
a5f75d66
AD
785
786 $ Define STORY once,upon,a,time,there,was
787 $ perl -e "for ($i = 0; $i <= 6; $i++) " -
740ce14c 788 _$ -e "{ print $ENV{'story;'.$i},' '}"
a5f75d66 789
f675dbe5
CB
790Perl will print C<ONCE UPON A TIME THERE WAS>, assuming, of course,
791that F<PERL_ENV_TABLES> is set up so that the logical name C<story>
792is found, rather than a CLI symbol or CRTL C<environ> element with
793the same name.
794
3eeba6fb 795When an element of C<%ENV> is set to a defined string, the
f675dbe5
CB
796corresponding definition is made in the location to which the
797first translation of F<PERL_ENV_TABLES> points. If this causes a
798logical name to be created, it is defined in supervisor mode.
3eeba6fb
CB
799(The same is done if an existing logical name was defined in
800executive or kernel mode; an existing user or supervisor mode
801logical name is reset to the new value.) If the value is an empty
802string, the logical name's translation is defined as a single NUL
803(ASCII 00) character, since a logical name cannot translate to a
804zero-length string. (This restriction does not apply to CLI symbols
805or CRTL C<environ> values; they are set to the empty string.)
f675dbe5
CB
806An element of the CRTL C<environ> array can be set only if your
807copy of Perl knows about the CRTL's C<setenv()> function. (This is
808present only in some versions of the DECCRTL; check C<$Config{d_setenv}>
809to see whether your copy of Perl was built with a CRTL that has this
810function.)
39aca757 811
3eeba6fb 812When an element of C<%ENV> is set to C<undef>,
f675dbe5
CB
813the element is looked up as if it were being read, and if it is
814found, it is deleted. (An item "deleted" from the CRTL C<environ>
815array is set to the empty string; this can only be done if your
816copy of Perl knows about the CRTL C<setenv()> function.) Using
817C<delete> to remove an element from C<%ENV> has a similar effect,
818but after the element is deleted, another attempt is made to
819look up the element, so an inner-mode logical name or a name in
820another location will replace the logical name just deleted.
3eeba6fb
CB
821In either case, only the first value found searching PERL_ENV_TABLES
822is altered. It is not possible at present to define a search list
823logical name via %ENV.
f675dbe5
CB
824
825The element C<$ENV{DEFAULT}> is special: when read, it returns
826Perl's current default device and directory, and when set, it
827resets them, regardless of the definition of F<PERL_ENV_TABLES>.
828It cannot be cleared or deleted; attempts to do so are silently
829ignored.
b7b1864f
CB
830
831Note that if you want to pass on any elements of the
832C-local environ array to a subprocess which isn't
833started by fork/exec, or isn't running a C program, you
834can "promote" them to logical names in the current
835process, which will then be inherited by all subprocesses,
836by saying
837
838 foreach my $key (qw[C-local keys you want promoted]) {
376ae1f1
PP
839 my $temp = $ENV{$key}; # read from C-local array
840 $ENV{$key} = $temp; # and define as logical name
b7b1864f
CB
841 }
842
843(You can't just say C<$ENV{$key} = $ENV{$key}>, since the
844Perl optimizer is smart enough to elide the expression.)
a5f75d66 845
6be8f7a6
JH
846Don't try to clear C<%ENV> by saying C<%ENV = ();>, it will throw
847a fatal error. This is equivalent to doing the following from DCL:
848
849 DELETE/LOGICAL *
850
851You can imagine how bad things would be if, for example, the SYS$MANAGER
852or SYS$SYSTEM logicals were deleted.
4a0d0822 853
740ce14c 854At present, the first time you iterate over %ENV using
edc7bc49
CB
855C<keys>, or C<values>, you will incur a time penalty as all
856logical names are read, in order to fully populate %ENV.
857Subsequent iterations will not reread logical names, so they
858won't be as slow, but they also won't reflect any changes
f675dbe5
CB
859to logical name tables caused by other programs.
860
861You do need to be careful with the logicals representing process-permanent
862files, such as C<SYS$INPUT> and C<SYS$OUTPUT>. The translations for these
863logicals are prepended with a two-byte binary value (0x1B 0x00) that needs to be
39aca757 864stripped off if you want to use it. (In previous versions of Perl it wasn't
f675dbe5
CB
865possible to get the values of these logicals, as the null byte acted as an
866end-of-string marker)
a5f75d66 867
a5f75d66
AD
868=item $!
869
870The string value of C<$!> is that returned by the CRTL's
871strerror() function, so it will include the VMS message for
872VMS-specific errors. The numeric value of C<$!> is the
873value of C<errno>, except if errno is EVMSERR, in which
874case C<$!> contains the value of vaxc$errno. Setting C<$!>
4e592037
PP
875always sets errno to the value specified. If this value is
876EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-NOMSG), so
877that the string value of C<$!> won't reflect the VMS error
878message from before C<$!> was set.
879
880=item $^E
881
882This variable provides direct access to VMS status values
883in vaxc$errno, which are often more specific than the
884generic Unix-style error messages in C<$!>. Its numeric value
885is the value of vaxc$errno, and its string value is the
886corresponding VMS message string, as retrieved by sys$getmsg().
887Setting C<$^E> sets vaxc$errno to the value specified.
888
4fdae800
PP
889=item $?
890
891The "status value" returned in C<$?> is synthesized from the
892actual exit status of the subprocess in a way that approximates
893POSIX wait(5) semantics, in order to allow Perl programs to
894portably test for successful completion of subprocesses. The
895low order 8 bits of C<$?> are always 0 under VMS, since the
896termination status of a process may or may not have been
897generated by an exception. The next 8 bits are derived from
39aca757 898the severity portion of the subprocess' exit status: if the
4fdae800 899severity was success or informational, these bits are all 0;
9bc98430
CB
900if the severity was warning, they contain a value of 1; if the
901severity was error or fatal error, they contain the actual
902severity bits, which turns out to be a value of 2 for error
903and 4 for fatal error.
904
4fdae800
PP
905As a result, C<$?> will always be zero if the subprocess' exit
906status indicated successful completion, and non-zero if a
9bc98430
CB
907warning or error occurred. Conversely, when setting C<$?> in
908an END block, an attempt is made to convert the POSIX value
909into a native status intelligible to the operating system upon
910exiting Perl. What this boils down to is that setting C<$?>
911to zero results in the generic success value SS$_NORMAL, and
912setting C<$?> to a non-zero value results in the generic
913failure status SS$_ABORT. See also L<perlport/exit>.
4fdae800 914
1b0c4952 915The pragma C<use vmsish 'status'> makes C<$?> reflect the actual
9bc98430
CB
916VMS exit status instead of the default emulation of POSIX status
917described above. This pragma also disables the conversion of
918non-zero values to SS$_ABORT when setting C<$?> in an END
919block (but zero will still be converted to SS$_NORMAL).
4fdae800 920
4e592037
PP
921=item $|
922
923Setting C<$|> for an I/O stream causes data to be flushed
924all the way to disk on each write (I<i.e.> not just to
925the underlying RMS buffers for a file). In other words,
926it's equivalent to calling fflush() and fsync() from C.
a5f75d66 927
55497cff
PP
928=back
929
bf99883d
HM
930=head1 Standard modules with VMS-specific differences
931
932=head2 SDBM_File
933
270c2ced 934SDBM_File works properly on VMS. It has, however, one minor
4a4eefd0
GS
935difference. The database directory file created has a F<.sdbm_dir>
936extension rather than a F<.dir> extension. F<.dir> files are VMS filesystem
bf99883d
HM
937directory files, and using them for other purposes could cause unacceptable
938problems.
939
748a9306 940=head1 Revision date
a0d0e21e 941
1506e54c 942This document was last updated on 01-May-2002, for Perl 5,
9bc98430 943patchlevel 8.
e518068a
PP
944
945=head1 AUTHOR
946
376ae1f1
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947Charles Bailey bailey@cor.newman.upenn.edu
948Craig Berry craigberry@mac.com
949Dan Sugalski dan@sidhe.org