-=head1 Notes on Perl5 for VMS
+=head1 NAME
-Gathered below are notes describing details of perl 5's
-behavior on VMS. They are a supplement to the regular perl 5
-documentation, so we have focussed on the ways in which perl
-5 functions differently under VMS thatn it does under Unix,
-and on teh interactions between perl and the rest of the
+perlvms - VMS-specific documentation for Perl
+
+=head1 DESCRIPTION
+
+Gathered below are notes describing details of Perl 5's
+behavior on VMS. They are a supplement to the regular Perl 5
+documentation, so we have focussed on the ways in which Perl
+5 functions differently under VMS than it does under Unix,
+and on the interactions between Perl and the rest of the
operating system. We haven't tried to duplicate complete
-descriptions of perl5 features from the main perl
+descriptions of Perl features from the main Perl
documentation, which can be found in the F<[.pod]>
-subdirectory of the perl 5 distribution.
+subdirectory of the Perl distribution.
We hope these notes will save you from confusion and lost
-sleep when writing perl scripts on VMS. If you find we've
+sleep when writing Perl scripts on VMS. If you find we've
missed something you think should appear here, please don't
-hesitate to drop a line to vmsperl@genetics.upenn.edu.
-
-=head2 Installation
-
-Directions for building and installing perl 5 can be found in
-the file F<ReadMe.VMS> in the main source directory of the
-perl5 distribution..
-
-=head2 File specifications
-
-We have tried to make perl aware of both VMS-style and Unix-
+hesitate to drop a line to vmsperl@newman.upenn.edu.
+
+=head1 Installation
+
+Directions for building and installing Perl 5 can be found in
+the file F<README.vms> in the main source directory of the
+Perl distribution..
+
+=head1 Organization of Perl Images
+
+=head2 Core Images
+
+During the installation process, three Perl images are produced.
+F<Miniperl.Exe> is an executable image which contains all of
+the basic functionality of Perl, but cannot take advantage of
+Perl extensions. It is used to generate several files needed
+to build the complete Perl and various extensions. Once you've
+finished installing Perl, you can delete this image.
+
+Most of the complete Perl resides in the shareable image
+F<PerlShr.Exe>, which provides a core to which the Perl executable
+image and all Perl extensions are linked. You should place this
+image in F<Sys$Share>, or define the logical name F<PerlShr> to
+translate to the full file specification of this image. It should
+be world readable. (Remember that if a user has execute only access
+to F<PerlShr>, VMS will treat it as if it were a privileged shareable
+image, and will therefore require all downstream shareable images to be
+INSTALLed, etc.)
+
+
+Finally, F<Perl.Exe> is an executable image containing the main
+entry point for Perl, as well as some initialization code. It
+should be placed in a public directory, and made world executable.
+In order to run Perl with command line arguments, you should
+define a foreign command to invoke this image.
+
+=head2 Perl Extensions
+
+Perl extensions are packages which provide both XS and Perl code
+to add new functionality to perl. (XS is a meta-language which
+simplifies writing C code which interacts with Perl, see
+L<perlxs> for more details.) The Perl code for an
+extension is treated like any other library module - it's
+made available in your script through the appropriate
+C<use> or C<require> statement, and usually defines a Perl
+package containing the extension.
+
+The portion of the extension provided by the XS code may be
+connected to the rest of Perl in either of two ways. In the
+B<static> configuration, the object code for the extension is
+linked directly into F<PerlShr.Exe>, and is initialized whenever
+Perl is invoked. In the B<dynamic> configuration, the extension's
+machine code is placed into a separate shareable image, which is
+mapped by Perl's DynaLoader when the extension is C<use>d or
+C<require>d in your script. This allows you to maintain the
+extension as a separate entity, at the cost of keeping track of the
+additional shareable image. Most extensions can be set up as either
+static or dynamic.
+
+The source code for an extension usually resides in its own
+directory. At least three files are generally provided:
+I<Extshortname>F<.xs> (where I<Extshortname> is the portion of
+the extension's name following the last C<::>), containing
+the XS code, I<Extshortname>F<.pm>, the Perl library module
+for the extension, and F<Makefile.PL>, a Perl script which uses
+the C<MakeMaker> library modules supplied with Perl to generate
+a F<Descrip.MMS> file for the extension.
+
+=head2 Installing static extensions
+
+Since static extensions are incorporated directly into
+F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a
+new extension. You should edit the main F<Descrip.MMS> or F<Makefile>
+you use to build Perl, adding the extension's name to the C<ext>
+macro, and the extension's object file to the C<extobj> macro.
+You'll also need to build the extension's object file, either
+by adding dependencies to the main F<Descrip.MMS>, or using a
+separate F<Descrip.MMS> for the extension. Then, rebuild
+F<PerlShr.Exe> to incorporate the new code.
+
+Finally, you'll need to copy the extension's Perl library
+module to the F<[.>I<Extname>F<]> subdirectory under one
+of the directories in C<@INC>, where I<Extname> is the name
+of the extension, with all C<::> replaced by C<.> (e.g.
+the library module for extension Foo::Bar would be copied
+to a F<[.Foo.Bar]> subdirectory).
+
+=head2 Installing dynamic extensions
+
+In general, the distributed kit for a Perl extension includes
+a file named Makefile.PL, which is a Perl program which is used
+to create a F<Descrip.MMS> file which can be used to build and
+install the files required by the extension. The kit should be
+unpacked into a directory tree B<not> under the main Perl source
+directory, and the procedure for building the extension is simply
+
+ $ perl Makefile.PL ! Create Descrip.MMS
+ $ mmk ! Build necessary files
+ $ mmk test ! Run test code, if supplied
+ $ mmk install ! Install into public Perl tree
+
+I<N.B.> The procedure by which extensions are built and
+tested creates several levels (at least 4) under the
+directory in which the extension's source files live.
+For this reason, you shouldn't nest the source directory
+too deeply in your directory structure, lest you eccedd RMS'
+maximum of 8 levels of subdirectory in a filespec. (You
+can use rooted logical names to get another 8 levels of
+nesting, if you can't place the files near the top of
+the physical directory structure.)
+
+VMS support for this process in the current release of Perl
+is sufficient to handle most extensions. However, it does
+not yet recognize extra libraries required to build shareable
+images which are part of an extension, so these must be added
+to the linker options file for the extension by hand. For
+instance, if the F<PGPLOT> extension to Perl requires the
+F<PGPLOTSHR.EXE> shareable image in order to properly link
+the Perl extension, then the line C<PGPLOTSHR/Share> must
+be added to the linker options file F<PGPLOT.Opt> produced
+during the build process for the Perl extension.
+
+By default, the shareable image for an extension is placed
+F<[.lib.site_perl.auto>I<Arch>.I<Extname>F<]> directory of the
+installed Perl directory tree (where I<Arch> is F<VMS_VAX> or
+F<VMS_AXP>, and I<Extname> is the name of the extension, with
+each C<::> translated to C<.>). (See the MakeMaker documentation
+for more details on installation options for extensions.)
+However, it can be manually placed in any of several locations:
+ - the F<[.Lib.Auto.>I<Arch>I<$PVers>I<Extname>F<]> subdirectory
+ of one of the directories in C<@INC> (where I<PVers>
+ is the version of Perl you're using, as supplied in C<$]>,
+ with '.' converted to '_'), or
+ - one of the directories in C<@INC>, or
+ - a directory which the extensions Perl library module
+ passes to the DynaLoader when asking it to map
+ the shareable image, or
+ - F<Sys$Share> or F<Sys$Library>.
+If the shareable image isn't in any of these places, you'll need
+to define a logical name I<Extshortname>, where I<Extshortname>
+is the portion of the extension's name after the last C<::>, which
+translates to the full file specification of the shareable image.
+
+=head1 File specifications
+
+=head2 Syntax
+
+We have tried to make Perl aware of both VMS-style and Unix-
style file specifications wherever possible. You may use
either style, or both, on the command line and in scripts,
but you may not combine the two styles within a single fle
-specfication. Filenames are, of course, still case-
-insensitive. For consistency, most perl5 routines return
-filespecs using lower case latters only, regardless of the
-case used in the arguments passed to them. (This is true
-only when running under VMS; perl5 respects the case-
-sensitivity of OSs like Unix.)
-
-We've tried to minimize the dependence of perl library
+specification. VMS Perl interprets Unix pathnames in much
+the same way as the CRTL (I<e.g.> the first component of
+an absolute path is read as the device name for the
+VMS file specification). There are a set of functions
+provided in the C<VMS::Filespec> package for explicit
+interconversion between VMS and Unix syntax; its
+documentation provides more details.
+
+Filenames are, of course, still case-insensitive. For
+consistency, most Perl routines return filespecs using
+lower case letters only, regardless of the case used in
+the arguments passed to them. (This is true only when
+running under VMS; Perl respects the case-sensitivity
+of OSs like Unix.)
+
+We've tried to minimize the dependence of Perl library
modules on Unix syntax, but you may find that some of these,
as well as some scripts written for Unix systems, will
require that you use Unix syntax, since they will assume that
-'/' is the directory separator, etc. If you find instances
-of this in the perl distribution itself, please let us know,
+'/' is the directory separator, I<etc.> If you find instances
+of this in the Perl distribution itself, please let us know,
so we can try to work around them.
-=head2 Command line redirection
+=head2 Wildcard expansion
+
+File specifications containing wildcards are allowed both on
+the command line and within Perl globs (e.g. <CE<lt>*.cE<gt>>). If
+the wildcard filespec uses VMS syntax, the resultant
+filespecs will follow VMS syntax; if a Unix-style filespec is
+passed in, Unix-style filespecs will be returned.
+
+In both cases, VMS wildcard expansion is performed. (csh-style
+wildcard expansion is available if you use C<File::Glob::glob>.)
+If the wildcard filespec contains a device or directory
+specification, then the resultant filespecs will also contain
+a device and directory; otherwise, device and directory
+information are removed. VMS-style resultant filespecs will
+contain a full device and directory, while Unix-style
+resultant filespecs will contain only as much of a directory
+path as was present in the input filespec. For example, if
+your default directory is Perl_Root:[000000], the expansion
+of C<[.t]*.*> will yield filespecs like
+"perl_root:[t]base.dir", while the expansion of C<t/*/*> will
+yield filespecs like "t/base.dir". (This is done to match
+the behavior of glob expansion performed by Unix shells.)
+
+Similarly, the resultant filespec will contain the file version
+only if one was present in the input filespec.
+
+=head2 Pipes
+
+Input and output pipes to Perl filehandles are supported; the
+"file name" is passed to lib$spawn() for asynchronous
+execution. You should be careful to close any pipes you have
+opened in a Perl script, lest you leave any "orphaned"
+subprocesses around when Perl exits.
+
+You may also use backticks to invoke a DCL subprocess, whose
+output is used as the return value of the expression. The
+string between the backticks is handled as if it were the
+argument to the C<system> operator (see below). In this case,
+Perl will wait for the subprocess to complete before continuing.
+
+=head1 PERL5LIB and PERLLIB
+
+The PERL5LIB and PERLLIB logical names work as documented L<perl>,
+except that the element separator is '|' instead of ':'. The
+directory specifications may use either VMS or Unix syntax.
+
+=head1 Command line
+
+=head2 I/O redirection and backgrounding
Perl for VMS supports redirection of input and output on the
command line, using a subset of Bourne shell syntax:
+
<F<file> reads stdin from F<file>,
>F<file> writes stdout to F<file>,
>>F<file> appends stdout to F<file>,
- 2>F<file> wrtits stderr to F<file>, and
+ 2>F<file> writes stderr to F<file>, and
2>>F<file> appends stderr to F<file>.
In addition, output may be piped to a subprocess, using the
character '|'. Anything after this character on the command
line is passed to a subprocess for execution; the subprocess
-takes the output of perl as its input.
+takes the output of Perl as its input.
Finally, if the command line ends with '&', the entire
command is run in the background as an asynchronous
subprocess.
-=head2 Pipes
+=head2 Command line switches
-Input and output pipes to perl filehandles are supported; the
-"file name" is passed to lib$spawn() for asynchronous
-execution. You should be careful to close any pipes you have
-opened in a perl script, lest you leave any "orphaned"
-subprocesses around when perl exits.
+The following command line switches behave differently under
+VMS than described in L<perlrun>. Note also that in order
+to pass uppercase switches to Perl, you need to enclose
+them in double-quotes on the command line, since the CRTL
+downcases all unquoted strings.
-You may also use backticks to invoke a DCL subprocess, whose
-output is used as the return value of the expression. The
-string between the backticks is passed directly to lib$spawn
-as the command to execute. In this case, perl will wait for
-the subprocess to complete before continuing.
+=over 4
-=head2 Wildcard expansion
+=item -i
-File specifications containing wildcards are allowed both on
-the command line and within perl globs (e.g. <C<*.c>>). If
-the wildcard filespec uses VMS syntax, the resultant
-filespecs will follow VMS syntax; if a Unix-style filespec is
-passed in, Unix-style filespecs will be returned..
+If the C<-i> switch is present but no extension for a backup
+copy is given, then inplace editing creates a new version of
+a file; the existing copy is not deleted. (Note that if
+an extension is given, an existing file is renamed to the backup
+file, as is the case under other operating systems, so it does
+not remain as a previous version under the original filename.)
-If the wildcard filespec contains a device or directory
-specification, then the resultant filespecs will also contain
-a device and directory; otherwise, device and directory
-information are removed. VMS-style resultant filespecs will
-contain a full device and directory, while Unix-style
-resultant filespecs will contain only as much of a directory
-path as was present in the input filespec. For example, if
-your default directory is Perl_Root:[000000], the expansion
-of C<[.t]*.*> will yield filespecs like
-"perl_root:[t]base.dir", while the expansion of C<t/*/*> will
-yield filespecs like "t/base.dir". (This is done to match
-the behavior of glob expansion performed by Unix shells.)
+=item -S
-Similarly, the resultant filespec will the file version only
-if one was present in the input filespec.
-
-=head2 %ENV
-
-Reading the elements of the %ENV array returns the
-translation of the logical name specified by the key,
-according to the normal search order of access modes and
-logical name tables. In addition, the keys C<home>,
-C<path>,C<term>, and C<user> return the CRTL "environment
-variables" of the same names. The key C<default> returns the
-current default device and directory specification.
-
-Setting an element of %ENV defines a supervisor-mode logical
-name in the process logical name table. B<Undef>ing or
-B<delete>ing an element of %ENV deletes the equivalent user-
-mode or supervisor-mode logical name from the process logical
-name table. If you use B<undef>, the %ENV element remains
-empty. If you use B<delete>, another attempt is made at
-logical name translation after the deletion, so an inner-mode
-logical name or a name in another logical name table will
-replace the logical name just deleted.
+If the C<-S> switch is present I<and> the script name does
+not contain a directory, then Perl translates the logical
+name DCL$PATH as a searchlist, using each translation as
+a directory in which to look for the script. In addition,
+if no file type is specified, Perl looks in each directory
+for a file matching the name specified, with a blank type,
+a type of F<.pl>, and a type of F<.com>, in that order.
-In all operations on %ENV, the key string is treated as if it
-were entirely uppercase, regardless of the case actually
-specified in the perl expression.
+=item -u
+
+The C<-u> switch causes the VMS debugger to be invoked
+after the Perl program is compiled, but before it has
+run. It does not create a core dump file.
-=head2 Perl functions
+=back
+
+=head1 Perl functions
As of the time this document was last revised, the following
-perl functions were implemented in the VMS port of perl
+Perl functions were implemented in the VMS port of Perl
(functions marked with * are discussed in more detail below):
- file tests*, abs, alarm, atan, binmode*, bless,
+ file tests*, abs, alarm, atan, backticks*, binmode*, bless,
caller, chdir, chmod, chown, chomp, chop, chr,
- close, closedir, cos, defined, delete, die, do,
- each, eof, eval, exec*, exists, exit, exp, fileno,
- fork*, getc, glob, goto, grep, hex, import, index,
- int, join, keys, kill, last, lc, lcfirst, length,
- local, localtime, log, m//, map, mkdir, my, next,
- no, oct, open, opendir, ord, pack, pipe, pop, pos,
- print, printf, push, q//, qq//, qw//, qx//,
- quotemeta, rand, read, readdir, redo, ref, rename,
+ close, closedir, cos, crypt*, defined, delete,
+ die, do, dump*, each, endpwent, eof, eval, exec*,
+ exists, exit, exp, fileno, fork*, getc, getlogin,
+ getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto,
+ grep, hex, import, index, int, join, keys, kill*,
+ last, lc, lcfirst, length, local, localtime, log, m//,
+ map, mkdir, my, next, no, oct, open, opendir, ord, pack,
+ pipe, pop, pos, print, printf, push, q//, qq//, qw//,
+ qx//*, quotemeta, rand, read, readdir, redo, ref, rename,
require, reset, return, reverse, rewinddir, rindex,
- rmdir, s///, scalar, seek, seekdir, select(internal)*,
- shift, sin, sleep, sort, splice, split, sprintf,
- sqrt, srand, stat, study, substr, sysread, system*,
- syswrite, tell, telldir, tie, time, times*, tr///,
- uc, ucfirst, umask, undef, unlink, unpack, untie,
- unshift, use, values, vec, wait, wantarray, warn,
- write, y///
+ rmdir, s///, scalar, seek, seekdir, select(internal),
+ select (system call)*, setpwent, shift, sin, sleep,
+ sort, splice, split, sprintf, sqrt, srand, stat,
+ study, substr, sysread, system*, syswrite, tell,
+ telldir, tie, time, times*, tr///, uc, ucfirst, umask,
+ undef, unlink*, unpack, untie, unshift, use, utime*,
+ values, vec, wait, waitpid*, wantarray, warn, write, y///
The following functions were not implemented in the VMS port,
and calling them produces a fatal error (usually) or
undefined behavior (rarely, we hope):
- chroot, crypt, dbmclose, dbmopen, dump, fcntl,
- flock, getlogin, getpgrp, getppid, getpriority,
- getpwent, getgrent, kill, getgrgid, getgrnam,
- getpwnam, getpwuid, setpwent, setgrent,
- endpwent, endgrent, gmtime, ioctl, link, lstst,
- msgctl, msgget, msgsend, msgrcv, readlink,
- select(system call), semctl, semget, semop,
- setpgrp, setpriority, shmctl, shmget, shmread,
- shmwrite, socketpair, symlink, syscall, truncate,
- utime, waitpid
+ chroot, dbmclose, dbmopen, fcntl, flock,
+ getpgrp, getppid, getpriority, getgrent, getgrgid,
+ getgrnam, setgrent, endgrent, ioctl, link, lstat,
+ msgctl, msgget, msgsend, msgrcv, readlink, semctl,
+ semget, semop, setpgrp, setpriority, shmctl, shmget,
+ shmread, shmwrite, socketpair, symlink, syscall
+
+The following functions are available on Perls compiled with Dec C 5.2 or
+greater and running VMS 7.0 or greater
+
+ truncate
The following functions may or may not be implemented,
depending on what type of socket support you've built into
-your copy of perl:
+your copy of Perl:
+
accept, bind, connect, getpeername,
gethostbyname, getnetbyname, getprotobyname,
getservbyname, gethostbyaddr, getnetbyaddr,
getnetent, getprotoent, getservent, sethostent,
setnetent, setprotoent, setservent, endhostent,
endnetent, endprotoent, endservent, getsockname,
- getsockopt, listen, recv, send, setsockopt,
- shutdown, socket
+ getsockopt, listen, recv, select(system call)*,
+ send, setsockopt, shutdown, socket
+=over 4
=item File tests
-The tests -b, -B, -c, -C, -d, -e, -f, -o, -M, -s, -S, -t, -T,
-and -z work as advertised. The return values for -r, -w, and
--x tell you whether you can actually access the file; this
-may mot reflect the UIC-based file protections. Since real
-and effective UIC don't differ under VMS, -O, -R, -W, and -X
-are equivalent to -o, -r, -w, and -x. Similarly, several
-other tests, including -A, -g, -k, -l,-p, and -u, aren't
-particularly meaningful under VMS, and the values returned by
-these tests reflect whatever your CRTL stat() routine does to
-the equivalent bits in the st_mode field.
-
-=item binmode
-
-The B<binmode> operator has no effect under VMS. It will
-return TRUE whenever called, but will not affect I/O
-operations on the filehandle given as its argument.
-
-=item exec
-
-The B<exec> operator behaves in one of two different ways.
-If called after a call to B<fork>, it will invoke the CRTL
-L<execv()> routine, passing its arguments to the subprocess
-created by B<fork> for execution. In this case, it is
-subject to all limitation that affect L<execv>. (In
+The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>,
+C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as
+advertised. The return values for C<-r>, C<-w>, and C<-x>
+tell you whether you can actually access the file; this may
+not reflect the UIC-based file protections. Since real and
+effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>,
+and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>.
+Similarly, several other tests, including C<-A>, C<-g>, C<-k>,
+C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under
+VMS, and the values returned by these tests reflect whatever
+your CRTL C<stat()> routine does to the equivalent bits in the
+st_mode field. Finally, C<-d> returns true if passed a device
+specification without an explicit directory (e.g. C<DUA1:>), as
+well as if passed a directory.
+
+Note: Some sites have reported problems when using the file-access
+tests (C<-r>, C<-w>, and C<-x>) on files accessed via DEC's DFS.
+Specifically, since DFS does not currently provide access to the
+extended file header of files on remote volumes, attempts to
+examine the ACL fail, and the file tests will return false,
+with C<$!> indicating that the file does not exist. You can
+use C<stat> on these files, since that checks UIC-based protection
+only, and then manually check the appropriate bits, as defined by
+your C compiler's F<stat.h>, in the mode value it returns, if you
+need an approximation of the file's protections.
+
+=item backticks
+
+Backticks create a subprocess, and pass the enclosed string
+to it for execution as a DCL command. Since the subprocess is
+created directly via C<lib$spawn()>, any valid DCL command string
+may be specified.
+
+=item binmode FILEHANDLE
+
+The C<binmode> operator will attempt to insure that no translation
+of carriage control occurs on input from or output to this filehandle.
+Since this involves reopening the file and then restoring its
+file position indicator, if this function returns FALSE, the
+underlying filehandle may no longer point to an open file, or may
+point to a different position in the file than before C<binmode>
+was called.
+
+Note that C<binmode> is generally not necessary when using normal
+filehandles; it is provided so that you can control I/O to existing
+record-structured files when necessary. You can also use the
+C<vmsfopen> function in the VMS::Stdio extension to gain finer
+control of I/O to files and devices with different record structures.
+
+=item crypt PLAINTEXT, USER
+
+The C<crypt> operator uses the C<sys$hash_password> system
+service to generate the hashed representation of PLAINTEXT.
+If USER is a valid username, the algorithm and salt values
+are taken from that user's UAF record. If it is not, then
+the preferred algorithm and a salt of 0 are used. The
+quadword encrypted value is returned as an 8-character string.
+
+The value returned by C<crypt> may be compared against
+the encrypted password from the UAF returned by the C<getpw*>
+functions, in order to authenticate users. If you're
+going to do this, remember that the encrypted password in
+the UAF was generated using uppercase username and
+password strings; you'll have to upcase the arguments to
+C<crypt> to insure that you'll get the proper value:
+
+ sub validate_passwd {
+ my($user,$passwd) = @_;
+ my($pwdhash);
+ if ( !($pwdhash = (getpwnam($user))[1]) ||
+ $pwdhash ne crypt("\U$passwd","\U$name") ) {
+ intruder_alert($name);
+ }
+ return 1;
+ }
+
+=item dump
+
+Rather than causing Perl to abort and dump core, the C<dump>
+operator invokes the VMS debugger. If you continue to
+execute the Perl program under the debugger, control will
+be transferred to the label specified as the argument to
+C<dump>, or, if no label was specified, back to the
+beginning of the program. All other state of the program
+(I<e.g.> values of variables, open file handles) are not
+affected by calling C<dump>.
+
+=item exec LIST
+
+The C<exec> operator behaves in one of two different ways.
+If called after a call to C<fork>, it will invoke the CRTL
+C<execv()> routine, passing its arguments to the subprocess
+created by C<fork> for execution. In this case, it is
+subject to all limitations that affect C<execv()>. (In
particular, this usually means that the command executed in
the subprocess must be an image compiled from C source code,
and that your options for passing file descriptors and signal
handlers to the subprocess are limited.)
-If the call to B<exec> does not follow a call to B<fork>, it
-will cause perl to exit, and to invoke the command given as
-an argument to B<exec> via lib$do_command. If the argument
-begins with a '$' (other than as part of a filespec), then it
+If the call to C<exec> does not follow a call to C<fork>, it
+will cause Perl to exit, and to invoke the command given as
+an argument to C<exec> via C<lib$do_command>. If the argument
+begins with '@' or '$' (other than as part of a filespec), then it
is executed as a DCL command. Otherwise, the first token on
the command line is treated as the filespec of an image to
run, and an attempt is made to invoke it (using F<.Exe> and
the process defaults to expand the filespec) and pass the
-rest of B<exec>'s argument to it as parameters.
-
-You can use B<exec> in both ways within the same script, as
-long as you call B<fork> and B<exec> in pairs. Perl only
-keeps track of whether B<fork> has been called since the last
-call to B<exec> when figuring out what to do, so multiple
-calls to B<fork> do not generate multiple levels of "fork
-context".
+rest of C<exec>'s argument to it as parameters. If the token
+has no file type, and matches a file with null type, then an
+attempt is made to determine whether the file is an executable
+image which should be invoked using C<MCR> or a text file which
+should be passed to DCL as a command procedure.
+
+You can use C<exec> in both ways within the same script, as
+long as you call C<fork> and C<exec> in pairs. Perl
+keeps track of how many times C<fork> and C<exec> have been
+called, and will call the CRTL C<execv()> routine if there have
+previously been more calls to C<fork> than to C<exec>.
=item fork
-The B<fork> operator works in the same way as the CRTL
-L<fork()> routine, which is quite different under VMS than
-under Unix. Sepcifically, while B<fork> returns 0 after it
-is called and the subprocess PID after B<exec> is called, in
+The C<fork> operator works in the same way as the CRTL
+C<vfork()> routine, which is quite different under VMS than
+under Unix. Specifically, while C<fork> returns 0 after it
+is called and the subprocess PID after C<exec> is called, in
both cases the thread of execution is within the parent
process, so there is no opportunity to perform operations in
-the subprocess before calling B<exec>.
+the subprocess before calling C<exec>.
-In general, the use of B<fork> and B<exec> to create
+In general, the use of C<fork> and C<exec> to create
subprocess is not recommended under VMS; wherever possible,
-use the B<system> operator or piped filehandles instead.
+use the C<system> operator or piped filehandles instead.
+
+=item getpwent
+
+=item getpwnam
+
+=item getpwuid
+
+These operators obtain the information described in L<perlfunc>,
+if you have the privileges necessary to retrieve the named user's
+UAF information via C<sys$getuai>. If not, then only the C<$name>,
+C<$uid>, and C<$gid> items are returned. The C<$dir> item contains
+the login directory in VMS syntax, while the C<$comment> item
+contains the login directory in Unix syntax. The C<$gcos> item
+contains the owner field from the UAF record. The C<$quota>
+item is not used.
+
+=item gmtime
+
+The C<gmtime> operator will function properly if you have a
+working CRTL C<gmtime()> routine, or if the logical name
+SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds
+which must be added to UTC to yield local time. (This logical
+name is defined automatically if you are running a version of
+VMS with built-in UTC support.) If neither of these cases is
+true, a warning message is printed, and C<undef> is returned.
+
+=item kill
+
+In most cases, C<kill> kill is implemented via the CRTL's C<kill()>
+function, so it will behave according to that function's
+documentation. If you send a SIGKILL, however, the $DELPRC system
+service is called directly. This insures that the target
+process is actually deleted, if at all possible. (The CRTL's C<kill()>
+function is presently implemented via $FORCEX, which is ignored by
+supervisor-mode images like DCL.)
-=item system
+Also, negative signal values don't do anything special under
+VMS; they're just converted to the corresponding positive value.
-The B<system> operator creates a subprocess, and passes its
+=item qx//
+
+See the entry on C<backticks> above.
+
+=item select (system call)
+
+If Perl was not built with socket support, the system call
+version of C<select> is not available at all. If socket
+support is present, then the system call version of
+C<select> functions only for file descriptors attached
+to sockets. It will not provide information about regular
+files or pipes, since the CRTL C<select()> routine does not
+provide this functionality.
+
+=item stat EXPR
+
+Since VMS keeps track of files according to a different scheme
+than Unix, it's not really possible to represent the file's ID
+in the C<st_dev> and C<st_ino> fields of a C<struct stat>. Perl
+tries its best, though, and the values it uses are pretty unlikely
+to be the same for two different files. We can't guarantee this,
+though, so caveat scriptor.
+
+=item system LIST
+
+The C<system> operator creates a subprocess, and passes its
arguments to the subprocess for execution as a DCL command.
-Since the subprocess is created directly via lib$spawn, any
-valid DCL command string may be specified. Perl waits for
-the subprocess to complete before continuing execution in the
-current process.
+Since the subprocess is created directly via C<lib$spawn()>, any
+valid DCL command string may be specified. If the string begins with
+'@', it is treated as a DCL command unconditionally. Otherwise, if
+the first token contains a character used as a delimiter in file
+specification (e.g. C<:> or C<]>), an attempt is made to expand it
+using a default type of F<.Exe> and the process defaults, and if
+successful, the resulting file is invoked via C<MCR>. This allows you
+to invoke an image directly simply by passing the file specification
+to C<system>, a common Unixish idiom. If the token has no file type,
+and matches a file with null type, then an attempt is made to
+determine whether the file is an executable image which should be
+invoked using C<MCR> or a text file which should be passed to DCL
+as a command procedure.
+
+If LIST consists of the empty string, C<system> spawns an
+interactive DCL subprocess, in the same fashion as typing
+B<SPAWN> at the DCL prompt.
+
+Perl waits for the subprocess to complete before continuing
+execution in the current process. As described in L<perlfunc>,
+the return value of C<system> is a fake "status" which follows
+POSIX semantics; see the description of C<$?> in this document
+for more detail. The actual VMS exit status of the subprocess
+is available in C<$^S> (as long as you haven't used another Perl
+function that resets C<$?> and C<$^S> in the meantime).
+
+=item time
+
+The value returned by C<time> is the offset in seconds from
+01-JAN-1970 00:00:00 (just like the CRTL's times() routine), in order
+to make life easier for code coming in from the POSIX/Unix world.
=item times
-The array returned by the B<times> operator is divided up
-according to the same rules the CRTL L<times()> routine.
+The array returned by the C<times> operator is divided up
+according to the same rules the CRTL C<times()> routine.
Therefore, the "system time" elements will always be 0, since
there is no difference between "user time" and "system" time
under VMS, and the time accumulated by subprocess may or may
not appear separately in the "child time" field, depending on
-whether L<times> keeps track of subprocesses separately.
-
-=head2 Revision date
+whether L<times> keeps track of subprocesses separately. Note
+especially that the VAXCRTL (at least) keeps track only of
+subprocesses spawned using L<fork> and L<exec>; it will not
+accumulate the times of subprocesses spawned via pipes, L<system>,
+or backticks.
+
+=item unlink LIST
+
+C<unlink> will delete the highest version of a file only; in
+order to delete all versions, you need to say
+ 1 while (unlink LIST);
+You may need to make this change to scripts written for a
+Unix system which expect that after a call to C<unlink>,
+no files with the names passed to C<unlink> will exist.
+(Note: This can be changed at compile time; if you
+C<use Config> and C<$Config{'d_unlink_all_versions'}> is
+C<define>, then C<unlink> will delete all versions of a
+file on the first call.)
+
+C<unlink> will delete a file if at all possible, even if it
+requires changing file protection (though it won't try to
+change the protection of the parent directory). You can tell
+whether you've got explicit delete access to a file by using the
+C<VMS::Filespec::candelete> operator. For instance, in order
+to delete only files to which you have delete access, you could
+say something like
+
+ sub safe_unlink {
+ my($file,$num);
+ foreach $file (@_) {
+ next unless VMS::Filespec::candelete($file);
+ $num += unlink $file;
+ }
+ $num;
+ }
+
+(or you could just use C<VMS::Stdio::remove>, if you've installed
+the VMS::Stdio extension distributed with Perl). If C<unlink> has to
+change the file protection to delete the file, and you interrupt it
+in midstream, the file may be left intact, but with a changed ACL
+allowing you delete access.
+
+=item utime LIST
+
+Since ODS-2, the VMS file structure for disk files, does not keep
+track of access times, this operator changes only the modification
+time of the file (VMS revision date).
+
+=item waitpid PID,FLAGS
+
+If PID is a subprocess started by a piped L<open>, C<waitpid>
+will wait for that subprocess, and return its final
+status value. If PID is a subprocess created in some other way
+(e.g. SPAWNed before Perl was invoked), or is not a subprocess of
+the current process, C<waitpid> will check once per second whether
+the process has completed, and when it has, will return 0. (If PID
+specifies a process that isn't a subprocess of the current process,
+and you invoked Perl with the C<-w> switch, a warning will be issued.)
+
+The FLAGS argument is ignored in all cases.
+
+=back
+
+=head1 Perl variables
+
+The following VMS-specific information applies to the indicated
+"special" Perl variables, in addition to the general information
+in L<perlvar>. Where there is a conflict, this information
+takes precedence.
+
+=over 4
+
+=item %ENV
+
+The operation of the C<%ENV> array depends on the translation
+of the logical name F<PERL_ENV_TABLES>. If defined, it should
+be a search list, each element of which specifies a location
+for C<%ENV> elements. If you tell Perl to read or set the
+element C<$ENV{>I<name>C<}>, then Perl uses the translations of
+F<PERL_ENV_TABLES> as follows:
+
+=over 4
+
+=item CRTL_ENV
+
+This string tells Perl to consult the CRTL's internal C<environ>
+array of key-value pairs, using I<name> as the key. In most cases,
+this contains only a few keys, but if Perl was invoked via the C
+C<exec[lv]e()> function, as is the case for CGI processing by some
+HTTP servers, then the C<environ> array may have been populated by
+the calling program.
+
+=item CLISYM_[LOCAL]
+
+A string beginning with C<CLISYM_>tells Perl to consult the CLI's
+symbol tables, using I<name> as the name of the symbol. When reading
+an element of C<%ENV>, the local symbol table is scanned first, followed
+by the global symbol table.. The characters following C<CLISYM_> are
+significant when an element of C<%ENV> is set or deleted: if the
+complete string is C<CLISYM_LOCAL>, the change is made in the local
+symbol table, otherwise the global symbol table is changed.
+
+=item Any other string
+
+If an element of F<PERL_ENV_TABLES> translates to any other string,
+that string is used as the name of a logical name table, which is
+consulted using I<name> as the logical name. The normal search
+order of access modes is used.
+
+=back
+
+F<PERL_ENV_TABLES> is translated once when Perl starts up; any changes
+you make while Perl is running do not affect the behavior of C<%ENV>.
+If F<PERL_ENV_TABLES> is not defined, then Perl defaults to consulting
+first the logical name tables specified by F<LNM$FILE_DEV>, and then
+the CRTL C<environ> array.
-This document was last updated on 16-Oct-1994, for perl 5,
-patchlevel 0.
+In all operations on %ENV, the key string is treated as if it
+were entirely uppercase, regardless of the case actually
+specified in the Perl expression.
+
+When an element of C<%ENV> is read, the locations to which
+F<PERL_ENV_TABLES> points are checked in order, and the value
+obtained from the first successful lookup is returned. If the
+name of the C<%ENV> element contains a semi-colon, it and
+any characters after it are removed. These are ignored when
+the CRTL C<environ> array or a CLI symbol table is consulted.
+However, the name is looked up in a logical name table, the
+suffix after the semi-colon is treated as the translation index
+to be used for the lookup. This lets you look up successive values
+for search list logical names. For instance, if you say
+
+ $ Define STORY once,upon,a,time,there,was
+ $ perl -e "for ($i = 0; $i <= 6; $i++) " -
+ _$ -e "{ print $ENV{'story;'.$i},' '}"
+
+Perl will print C<ONCE UPON A TIME THERE WAS>, assuming, of course,
+that F<PERL_ENV_TABLES> is set up so that the logical name C<story>
+is found, rather than a CLI symbol or CRTL C<environ> element with
+the same name.
+
+When an element of C<%ENV> is set to a defined string, the
+corresponding definition is made in the location to which the
+first translation of F<PERL_ENV_TABLES> points. If this causes a
+logical name to be created, it is defined in supervisor mode.
+(The same is done if an existing logical name was defined in
+executive or kernel mode; an existing user or supervisor mode
+logical name is reset to the new value.) If the value is an empty
+string, the logical name's translation is defined as a single NUL
+(ASCII 00) character, since a logical name cannot translate to a
+zero-length string. (This restriction does not apply to CLI symbols
+or CRTL C<environ> values; they are set to the empty string.)
+An element of the CRTL C<environ> array can be set only if your
+copy of Perl knows about the CRTL's C<setenv()> function. (This is
+present only in some versions of the DECCRTL; check C<$Config{d_setenv}>
+to see whether your copy of Perl was built with a CRTL that has this
+function.)
+
+When an element of C<%ENV> is set to C<undef>,
+the element is looked up as if it were being read, and if it is
+found, it is deleted. (An item "deleted" from the CRTL C<environ>
+array is set to the empty string; this can only be done if your
+copy of Perl knows about the CRTL C<setenv()> function.) Using
+C<delete> to remove an element from C<%ENV> has a similar effect,
+but after the element is deleted, another attempt is made to
+look up the element, so an inner-mode logical name or a name in
+another location will replace the logical name just deleted.
+In either case, only the first value found searching PERL_ENV_TABLES
+is altered. It is not possible at present to define a search list
+logical name via %ENV.
+
+The element C<$ENV{DEFAULT}> is special: when read, it returns
+Perl's current default device and directory, and when set, it
+resets them, regardless of the definition of F<PERL_ENV_TABLES>.
+It cannot be cleared or deleted; attempts to do so are silently
+ignored.
+
+Note that if you want to pass on any elements of the
+C-local environ array to a subprocess which isn't
+started by fork/exec, or isn't running a C program, you
+can "promote" them to logical names in the current
+process, which will then be inherited by all subprocesses,
+by saying
+
+ foreach my $key (qw[C-local keys you want promoted]) {
+ my $temp = $ENV{$key}; # read from C-local array
+ $ENV{$key} = $temp; # and define as logical name
+ }
+
+(You can't just say C<$ENV{$key} = $ENV{$key}>, since the
+Perl optimizer is smart enough to elide the expression.)
+
+At present, the first time you iterate over %ENV using
+C<keys>, or C<values>, you will incur a time penalty as all
+logical names are read, in order to fully populate %ENV.
+Subsequent iterations will not reread logical names, so they
+won't be as slow, but they also won't reflect any changes
+to logical name tables caused by other programs.
+
+You do need to be careful with the logicals representing process-permanent
+files, such as C<SYS$INPUT> and C<SYS$OUTPUT>. The translations for these
+logicals are prepended with a two-byte binary value (0x1B 0x00) that needs to be
+stripped off if you want to use it. (In previous versions of perl it wasn't
+possible to get the values of these logicals, as the null byte acted as an
+end-of-string marker)
+
+=item $!
+
+The string value of C<$!> is that returned by the CRTL's
+strerror() function, so it will include the VMS message for
+VMS-specific errors. The numeric value of C<$!> is the
+value of C<errno>, except if errno is EVMSERR, in which
+case C<$!> contains the value of vaxc$errno. Setting C<$!>
+always sets errno to the value specified. If this value is
+EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-NOMSG), so
+that the string value of C<$!> won't reflect the VMS error
+message from before C<$!> was set.
+
+=item $^E
+
+This variable provides direct access to VMS status values
+in vaxc$errno, which are often more specific than the
+generic Unix-style error messages in C<$!>. Its numeric value
+is the value of vaxc$errno, and its string value is the
+corresponding VMS message string, as retrieved by sys$getmsg().
+Setting C<$^E> sets vaxc$errno to the value specified.
+
+=item $?
+
+The "status value" returned in C<$?> is synthesized from the
+actual exit status of the subprocess in a way that approximates
+POSIX wait(5) semantics, in order to allow Perl programs to
+portably test for successful completion of subprocesses. The
+low order 8 bits of C<$?> are always 0 under VMS, since the
+termination status of a process may or may not have been
+generated by an exception. The next 8 bits are derived from
+severity portion of the subprocess' exit status: if the
+severity was success or informational, these bits are all 0;
+otherwise, they contain the severity value shifted left one bit.
+As a result, C<$?> will always be zero if the subprocess' exit
+status indicated successful completion, and non-zero if a
+warning or error occurred. The actual VMS exit status may
+be found in C<$^S> (q.v.).
+
+=item $^S
+
+Under VMS, this is the 32-bit VMS status value returned by the
+last subprocess to complete. Unlink C<$?>, no manipulation
+is done to make this look like a POSIX wait(5) value, so it
+may be treated as a normal VMS status value.
+
+=item $|
+
+Setting C<$|> for an I/O stream causes data to be flushed
+all the way to disk on each write (I<i.e.> not just to
+the underlying RMS buffers for a file). In other words,
+it's equivalent to calling fflush() and fsync() from C.
+
+=back
+
+=head1 Standard modules with VMS-specific differences
+
+=head2 SDBM_File
+
+SDBM_File works properly on VMS. It has, however, one minor
+difference. The database directory file created has a F<.sdbm_dir>
+extension rather than a F<.dir> extension. F<.dir> files are VMS filesystem
+directory files, and using them for other purposes could cause unacceptable
+problems.
+
+=head1 Revision date
+
+This document was last updated on 26-Feb-2000, for Perl 5,
+patchlevel 6.
+
+=head1 AUTHOR
+
+Charles Bailey <bailey@cor.newman.upenn.edu>
+Dan Sugalski <dan@sidhe.org>
https://perl5.git.perl.org / perl5.git / blobdiff