perlvms
(1)
Name
perlvms - specific documentation for Perl
Synopsis
Please see following description for synopsis
Description
Perl Programmers Reference Guide PERLVMS(1)
NAME
perlvms - VMS-specific documentation for Perl
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 Perl features from the main Perl
documentation, which can be found in the [.pod] 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
missed something you think should appear here, please don't
hesitate to drop a line to vmsperl@perl.org.
Installation
Directions for building and installing Perl 5 can be found
in the file README.vms in the main source directory of the
Perl distribution..
Organization of Perl Images
Core Images
During the installation process, three Perl images are
produced. 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
PerlShr.Exe, which provides a core to which the Perl
executable image and all Perl extensions are linked. You
should place this image in Sys$Share, or define the logical
name 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 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, 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.
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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 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 "use"
or "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
static configuration, the object code for the extension is
linked directly into PerlShr.Exe, and is initialized
whenever Perl is invoked. In the 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 "use"d or "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:
Extshortname.xs (where Extshortname is the portion of the
extension's name following the last "::"), containing the XS
code, Extshortname.pm, the Perl library module for the
extension, and Makefile.PL, a Perl script which uses the
"MakeMaker" library modules supplied with Perl to generate a
Descrip.MMS file for the extension.
Installing static extensions
Since static extensions are incorporated directly into
PerlShr.Exe, you'll have to rebuild Perl to incorporate a
new extension. You should edit the main Descrip.MMS or
Makefile you use to build Perl, adding the extension's name
to the "ext" macro, and the extension's object file to the
"extobj" macro. You'll also need to build the extension's
object file, either by adding dependencies to the main
Descrip.MMS, or using a separate Descrip.MMS for the
extension. Then, rebuild PerlShr.Exe to incorporate the new
code.
Finally, you'll need to copy the extension's Perl library
module to the [.Extname] subdirectory under one of the
directories in @INC, where Extname is the name of the
extension, with all "::" replaced by "." (e.g. the library
module for extension Foo::Bar would be copied to a
[.Foo.Bar] subdirectory).
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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 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 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
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 if
you are running a version of VMS prior to V7.1 you shouldn't
nest the source directory too deeply in your directory
structure lest you exceed 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 PGPLOT extension to Perl
requires the PGPLOTSHR.EXE shareable image in order to
properly link the Perl extension, then the line
"PGPLOTSHR/Share" must be added to the linker options file
PGPLOT.Opt produced during the build process for the Perl
extension.
By default, the shareable image for an extension is placed
in the [.lib.site_perl.autoArch.Extname] directory of the
installed Perl directory tree (where Arch is VMS_VAX or
VMS_AXP, and Extname is the name of the extension, with each
"::" translated to "."). (See the MakeMaker documentation
for more details on installation options for extensions.)
However, it can be manually placed in any of several
locations:
o the [.Lib.Auto.Arch$PVersExtname] subdirectory of one of
the directories in @INC (where PVers is the version of
Perl you're using, as supplied in $], with '.' converted
to '_'), or
o one of the directories in @INC, or
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o a directory which the extensions Perl library module
passes to the DynaLoader when asking it to map the
shareable image, or
o Sys$Share or Sys$Library.
If the shareable image isn't in any of these places, you'll
need to define a logical name Extshortname, where
Extshortname is the portion of the extension's name after
the last "::", which translates to the full file
specification of the shareable image.
File specifications
Syntax
We have tried to make Perl aware of both VMS-style and Unix-
style file specifications wherever possible. You may use
either style, or both, on the command line and in scripts,
but you may not combine the two styles within a single file
specification. VMS Perl interprets Unix pathnames in much
the same way as the CRTL (e.g. the first component of an
absolute path is read as the device name for the VMS file
specification). There are a set of functions provided in
the "VMS::Filespec" package for explicit interconversion
between VMS and Unix syntax; its documentation provides more
details.
We've tried to minimize the dependence of Perl library
modules on Unix syntax, but you may find that some of these,
as well as some scripts written for Unix systems, will
require that you use Unix syntax, since they will assume
that '/' is the directory separator, etc. If you find
instances of this in the Perl distribution itself, please
let us know, so we can try to work around them.
Also when working on Perl programs on VMS, if you need a
syntax in a specific operating system format, then you need
either to check the appropriate DECC$ feature logical, or
call a conversion routine to force it to that format.
The feature logical name DECC$FILENAME_UNIX_REPORT modifies
traditional Perl behavior in the conversion of file
specifications from Unix to VMS format in order to follow
the extended character handling rules now expected by the
CRTL. Specifically, when this feature is in effect, the
"./.../" in a Unix path is now translated to "[.^.^.^.]"
instead of the traditional VMS "[...]". To be compatible
with what MakeMaker expects, if a VMS path cannot be
translated to a Unix path, it is passed through unchanged,
so "unixify("[...]")" will return "[...]".
The handling of extended characters is largely complete in
the VMS-specific C infrastructure of Perl, but more work is
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still needed to fully support extended syntax filenames in
several core modules. In particular, at this writing
PathTools has only partial support for directories
containing some extended characters.
There are several ambiguous cases where a conversion routine
cannot determine whether an input filename is in Unix format
or in VMS format, since now both VMS and Unix file
specifications may have characters in them that could be
mistaken for syntax delimiters of the other type. So some
pathnames simply cannot be used in a mode that allows either
type of pathname to be present. Perl will tend to assume
that an ambiguous filename is in Unix format.
Allowing "." as a version delimiter is simply incompatible
with determining whether a pathname is in VMS format or in
Unix format with extended file syntax. There is no way to
know whether "perl-5.8.6" is a Unix "perl-5.8.6" or a VMS
"perl-5.8;6" when passing it to unixify() or vmsify().
The DECC$FILENAME_UNIX_REPORT logical name controls how Perl
interprets filenames to the extent that Perl uses the CRTL
internally for many purposes, and attempts to follow CRTL
conventions for reporting filenames. The
DECC$FILENAME_UNIX_ONLY feature differs in that it expects
all filenames passed to the C run-time to be already in Unix
format. This feature is not yet supported in Perl since
Perl uses traditional OpenVMS file specifications internally
and in the test harness, and it is not yet clear whether
this mode will be useful or useable. The feature logical
name DECC$POSIX_COMPLIANT_PATHNAMES is new with the RMS
Symbolic Link SDK and included with OpenVMS v8.3, but is not
yet supported in Perl.
Filename Case
Perl follows VMS defaults and override settings in
preserving (or not preserving) filename case. Case is not
preserved on ODS-2 formatted volumes on any architecture.
On ODS-5 volumes, filenames may be case preserved depending
on process and feature settings. Perl now honors
DECC$EFS_CASE_PRESERVE and DECC$ARGV_PARSE_STYLE on those
systems where the CRTL supports these features. When these
features are not enabled or the CRTL does not support them,
Perl follows the traditional CRTL behavior of downcasing
command-line arguments and returning file specifications in
lower case only.
N. B. It is very easy to get tripped up using a mixture of
other programs, external utilities, and Perl scripts that
are in varying states of being able to handle case
preservation. For example, a file created by an older
version of an archive utility or a build utility such as MMK
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or MMS may generate a filename in all upper case even on an
ODS-5 volume. If this filename is later retrieved by a Perl
script or module in a case preserving environment, that
upper case name may not match the mixed-case or lower-case
expections of the Perl code. Your best bet is to follow an
all-or-nothing approach to case preservation: either don't
use it at all, or make sure your entire toolchain and
application environment support and use it.
OpenVMS Alpha v7.3-1 and later and all version of OpenVMS
I64 support case sensitivity as a process setting (see "SET
PROCESS /CASE_LOOKUP=SENSITIVE"). Perl does not currently
suppport case sensitivity on VMS, but it may in the future,
so Perl programs should use the "File::Spec->case_tolerant"
method to determine the state, and not the $^O variable.
Symbolic Links
When built on an ODS-5 volume with symbolic links enabled,
Perl by default supports symbolic links when the requisite
support is available in the filesystem and CRTL (generally
64-bit OpenVMS v8.3 and later). There are a number of
limitations and caveats to be aware of when working with
symbolic links on VMS. Most notably, the target of a valid
symbolic link must be expressed as a Unix-style path and it
must exist on a volume visible from your POSIX root (see the
"SHOW ROOT" command in DCL help). For further details on
symbolic link capabilities and requirements, see chapter 12
of the CRTL manual that ships with OpenVMS v8.3 or later.
Wildcard expansion
File specifications containing wildcards are allowed both on
the command line and within Perl globs (e.g. "<*.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.
Similar to the behavior of wildcard globbing for a Unix
shell, one can escape command line wildcards with double
quotation marks """ around a perl program command line
argument. However, owing to the stripping of """ characters
carried out by the C handling of argv you will need to
escape a construct such as this one (in a directory
containing the files PERL.C, PERL.EXE, PERL.H, and
PERL.OBJ):
$ perl -e "print join(' ',@ARGV)" perl.*
perl.c perl.exe perl.h perl.obj
in the following triple quoted manner:
$ perl -e "print join(' ',@ARGV)" """perl.*"""
perl.*
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In both the case of unquoted command line arguments or in
calls to "glob()" VMS wildcard expansion is performed. (csh-
style wildcard expansion is available if you use
"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 "[.t]*.*" will yield
filespecs like "perl_root:[t]base.dir", while the expansion
of "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.
Pipes
Input and output pipes to Perl filehandles are supported;
the "file name" is passed to lib$spawn() for asynchronous
execution. You should be careful to close any pipes you
have opened in a Perl script, lest you leave any "orphaned"
subprocesses around when Perl exits.
You may also use backticks to invoke a DCL subprocess, whose
output is used as the return value of the expression. The
string between the backticks is handled as if it were the
argument to the "system" operator (see below). In this
case, Perl will wait for the subprocess to complete before
continuing.
The mailbox (MBX) that perl can create to communicate with a
pipe defaults to a buffer size of 8192 on 64-bit systems,
512 on VAX. The default buffer size is adjustable via the
logical name PERL_MBX_SIZE provided that the value falls
between 128 and the SYSGEN parameter MAXBUF inclusive. For
example, to set the mailbox size to 32767 use
"$ENV{'PERL_MBX_SIZE'} = 32767;" and then open and use pipe
constructs. An alternative would be to issue the command:
$ Define PERL_MBX_SIZE 32767
before running your wide record pipe program. A larger
value may improve performance at the expense of the BYTLM
UAF quota.
PERL5LIB and PERLLIB
The PERL5LIB and PERLLIB logical names work as documented in
perl, except that the element separator is '|' instead of
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':'. The directory specifications may use either VMS or
Unix syntax.
The Perl Forked Debugger
The Perl forked debugger places the debugger commands and
output in a separate X-11 terminal window so that commands
and output from multiple processes are not mixed together.
Perl on VMS supports an emulation of the forked debugger
when Perl is run on a VMS system that has X11 support
installed.
To use the forked debugger, you need to have the default
display set to an X-11 Server and some environment variables
set that Unix expects.
The forked debugger requires the environment variable "TERM"
to be "xterm", and the environment variable "DISPLAY" to
exist. "xterm" must be in lower case.
$define TERM "xterm"
$define DISPLAY "hostname:0.0"
Currently the value of "DISPLAY" is ignored. It is
recommended that it be set to be the hostname of the
display, the server and screen in Unix notation. In the
future the value of DISPLAY may be honored by Perl instead
of using the default display.
It may be helpful to always use the forked debugger so that
script I/O is separated from debugger I/O. You can force
the debugger to be forked by assigning a value to the
logical name <PERLDB_PIDS> that is not a process
identification number.
$define PERLDB_PIDS XXXX
PERL_VMS_EXCEPTION_DEBUG
The PERL_VMS_EXCEPTION_DEBUG being defined as "ENABLE" will
cause the VMS debugger to be invoked if a fatal exception
that is not otherwise handled is raised. The purpose of
this is to allow debugging of internal Perl problems that
would cause such a condition.
This allows the programmer to look at the execution stack
and variables to find out the cause of the exception. As
the debugger is being invoked as the Perl interpreter is
about to do a fatal exit, continuing the execution in debug
mode is usally not practical.
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Starting Perl in the VMS debugger may change the program
execution profile in a way that such problems are not
reproduced.
The "kill" function can be used to test this functionality
from within a program.
In typical VMS style, only the first letter of the value of
this logical name is actually checked in a case insensitive
mode, and it is considered enabled if it is the value
"T","1" or "E".
This logical name must be defined before Perl is started.
Command line
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:
o "<file" reads stdin from "file",
o ">file" writes stdout to "file",
o ">>file" appends stdout to "file",
o "2>file" writes stderr to "file",
o "2>>file" appends stderr to "file", and
o "2>&1" redirects stderr to stdout.
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.
Finally, if the command line ends with '&', the entire
command is run in the background as an asynchronous
subprocess.
Command line switches
The following command line switches behave differently under
VMS than described in 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.
On newer 64 bit versions of OpenVMS, a process setting now
controls if the quoting is needed to preserve the case of
command line arguments.
-i If the "-i" switch is present but no extension for a
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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.)
-S If the "-S" or "-"S"" switch is present 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 .pl, and a type
of .com, in that order.
-u The "-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.
Perl functions
As of the time this document was last revised, the following
Perl functions were implemented in the VMS port of Perl
(functions marked with * are discussed in more detail
below):
file tests*, abs, alarm, atan, backticks*, binmode*, bless,
caller, chdir, chmod, chown, chomp, chop, chr,
close, closedir, cos, crypt*, defined, delete, die, do, dump*,
each, endgrent, endpwent, eof, eval, exec*, exists, exit, exp,
fileno, flock getc, getgrent*, getgrgid*, getgrnam, getlogin, getppid,
getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto,
grep, hex, ioctl, import, index, int, join, keys, kill*,
last, lc, lcfirst, lchown*, length, link*, local, localtime, log, lstat, 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, readlink*, redo, ref, rename,
require, reset, return, reverse, rewinddir, rindex,
rmdir, s///, scalar, seek, seekdir, select(internal),
select (system call)*, setgrent, setpwent, shift, sin, sleep,
socketpair, sort, splice, split, sprintf, sqrt, srand, stat,
study, substr, symlink*, 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):
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chroot, dbmclose, dbmopen, fork*, getpgrp, getpriority,
msgctl, msgget, msgsend, msgrcv, semctl,
semget, semop, setpgrp, setpriority, shmctl, shmget,
shmread, shmwrite, 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 are available on Perls built on VMS
7.2 or greater:
fcntl (without locking)
The following functions may or may not be implemented,
depending on what type of socket support you've built into
your copy of Perl:
accept, bind, connect, getpeername,
gethostbyname, getnetbyname, getprotobyname,
getservbyname, gethostbyaddr, getnetbyaddr,
getprotobynumber, getservbyport, gethostent,
getnetent, getprotoent, getservent, sethostent,
setnetent, setprotoent, setservent, endhostent,
endnetent, endprotoent, endservent, getsockname,
getsockopt, listen, recv, select(system call)*,
send, setsockopt, shutdown, socket
The following function is available on Perls built on 64 bit
OpenVMS v8.2 with hard links enabled on an ODS-5 formatted
build disk. CRTL support is in principle available as of
OpenVMS v7.3-1, and better configuration support could
detect this.
link
The following functions are available on Perls built on 64
bit OpenVMS v8.2 and later. CRTL support is in principle
available as of OpenVMS v7.3-2, and better configuration
support could detect this.
getgrgid, getgrnam, getpwnam, getpwuid,
setgrent, ttyname
The following functions are available on Perls built on 64
bit OpenVMS v8.2 and later.
statvfs, socketpair
File tests
The tests "-b", "-B", "-c", "-C", "-d", "-e", "-f",
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"-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 not 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. Finally, "-d" returns true if passed a
device specification without an explicit directory (e.g.
"DUA1:"), as well as if passed a directory.
There are DECC feature logical names AND ODS-5 volume
attributes that also control what values are returned
for the date fields.
Note: Some sites have reported problems when using the
file-access tests ("-r", "-w", and "-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 $!
indicating that the file does not exist. You can use
"stat" on these files, since that checks UIC-based
protection only, and then manually check the appropriate
bits, as defined by your C compiler's stat.h, in the
mode value it returns, if you need an approximation of
the file's protections.
backticks
Backticks create a subprocess, and pass the enclosed
string to it for execution as a DCL command. Since the
subprocess is created directly via "lib$spawn()", any
valid DCL command string may be specified.
binmode FILEHANDLE
The "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 "binmode" was called.
Note that "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 "vmsfopen" function in
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the VMS::Stdio extension to gain finer control of I/O to
files and devices with different record structures.
crypt PLAINTEXT, USER
The "crypt" operator uses the "sys$hash_password" system
service to generate the hashed representation of
PLAINTEXT. If USER is a valid username, the algorithm
and salt values are taken from that user's UAF record.
If it is not, then the preferred algorithm and a salt of
0 are used. The quadword encrypted value is returned as
an 8-character string.
The value returned by "crypt" may be compared against
the encrypted password from the UAF returned by the
"getpw*" functions, in order to authenticate users. If
you're going to do this, remember that the encrypted
password in the UAF was generated using uppercase
username and password strings; you'll have to upcase the
arguments to "crypt" to insure that you'll get the
proper value:
sub validate_passwd {
my($user,$passwd) = @_;
my($pwdhash);
if ( !($pwdhash = (getpwnam($user))[1]) ||
$pwdhash ne crypt("\U$passwd","\U$name") ) {
intruder_alert($name);
}
return 1;
}
die "die" will force the native VMS exit status to be an
SS$_ABORT code if neither of the $! or $? status values
are ones that would cause the native status to be
interpreted as being what VMS classifies as SEVERE_ERROR
severity for DCL error handling.
When "PERL_VMS_POSIX_EXIT" is active (see "$?" below),
the native VMS exit status value will have either one of
the $! or $? or $^E or the Unix value 255 encoded into
it in a way that the effective original value can be
decoded by other programs written in C, including Perl
and the GNV package. As per the normal non-VMS behavior
of "die" if either $! or $? are non-zero, one of those
values will be encoded into a native VMS status value.
If both of the Unix status values are 0, and the $^E
value is set one of ERROR or SEVERE_ERROR severity, then
the $^E value will be used as the exit code as is. If
none of the above apply, the Unix value of 255 will be
encoded into a native VMS exit status value.
Please note a significant difference in the behavior of
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"die" in the "PERL_VMS_POSIX_EXIT" mode is that it does
not force a VMS SEVERE_ERROR status on exit. The Unix
exit values of 2 through 255 will be encoded in VMS
status values with severity levels of SUCCESS. The Unix
exit value of 1 will be encoded in a VMS status value
with a severity level of ERROR. This is to be
compatible with how the VMS C library encodes these
values.
The minimum severity level set by "die" in
"PERL_VMS_POSIX_EXIT" mode may be changed to be ERROR or
higher in the future depending on the results of testing
and further review.
See "$?" for a description of the encoding of the Unix
value to produce a native VMS status containing it.
dump
Rather than causing Perl to abort and dump core, the
"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 "dump", or, if no label was specified,
back to the beginning of the program. All other state
of the program (e.g. values of variables, open file
handles) are not affected by calling "dump".
exec LIST
A call to "exec" will cause Perl to exit, and to invoke
the command given as an argument to "exec" via
"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
.Exe and the process defaults to expand the filespec)
and pass the rest of "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 "MCR" or a text file which
should be passed to DCL as a command procedure.
fork
While in principle the "fork" operator could be
implemented via (and with the same rather severe
limitations as) the CRTL "vfork()" routine, and while
some internal support to do just that is in place, the
implementation has never been completed, making "fork"
currently unavailable. A true kernel "fork()" is
expected in a future version of VMS, and the pseudo-fork
based on interpreter threads may be available in a
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future version of Perl on VMS (see perlfork). In the
meantime, use "system", backticks, or piped filehandles
to create subprocesses.
getpwent
getpwnam
getpwuid
These operators obtain the information described in
perlfunc, if you have the privileges necessary to
retrieve the named user's UAF information via
"sys$getuai". If not, then only the $name, $uid, and
$gid items are returned. The $dir item contains the
login directory in VMS syntax, while the $comment item
contains the login directory in Unix syntax. The $gcos
item contains the owner field from the UAF record. The
$quota item is not used.
gmtime
The "gmtime" operator will function properly if you have
a working CRTL "gmtime()" routine, or if the logical
name SYS$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 "undef" is returned.
kill
In most cases, "kill" is implemented via the
undocumented system service $SIGPRC, which has the same
calling sequence as $FORCEX, but throws an exception in
the target process rather than forcing it to call $EXIT.
Generally speaking, "kill" follows the behavior of the
CRTL's "kill()" function, but unlike that function can
be called from within a signal handler. Also, unlike
the "kill" in some versions of the CRTL, Perl's "kill"
checks the validity of the signal passed in and returns
an error rather than attempting to send an unrecognized
signal.
Also, negative signal values don't do anything special
under VMS; they're just converted to the corresponding
positive value.
qx//
See the entry on "backticks" above.
select (system call)
If Perl was not built with socket support, the system
call version of "select" is not available at all. If
socket support is present, then the system call version
of "select" functions only for file descriptors attached
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to sockets. It will not provide information about
regular files or pipes, since the CRTL "select()"
routine does not provide this functionality.
stat EXPR
Since VMS keeps track of files according to a different
scheme than Unix, it's not really possible to represent
the file's ID in the "st_dev" and "st_ino" fields of a
"struct stat". Perl tries its best, though, and the
values it uses are pretty unlikely to be the same for
two different files. We can't guarantee this, though,
so caveat scriptor.
system LIST
The "system" operator creates a subprocess, and passes
its arguments to the subprocess for execution as a DCL
command. Since the subprocess is created directly via
"lib$spawn()", any valid DCL command string may be
specified. 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. ":" or "]"), an attempt is made
to expand it using a default type of .Exe and the
process defaults, and if successful, the resulting file
is invoked via "MCR". This allows you to invoke an image
directly simply by passing the file specification to
"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 "MCR" or
a text file which should be passed to DCL as a command
procedure.
If LIST consists of the empty string, "system" spawns an
interactive DCL subprocess, in the same fashion as
typing SPAWN at the DCL prompt.
Perl waits for the subprocess to complete before
continuing execution in the current process. As
described in perlfunc, the return value of "system" is a
fake "status" which follows POSIX semantics unless the
pragma "use vmsish 'status'" is in effect; see the
description of $? in this document for more detail.
time
The value returned by "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.
times
The array returned by the "times" operator is divided up
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according to the same rules the CRTL "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 a
subprocess may or may not appear separately in the
"child time" field, depending on whether times keeps
track of subprocesses separately. Note especially that
the VAXCRTL (at least) keeps track only of subprocesses
spawned using fork and exec; it will not accumulate the
times of subprocesses spawned via pipes, system, or
backticks.
unlink LIST
"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
"unlink", no files with the names passed to "unlink"
will exist. (Note: This can be changed at compile time;
if you "use Config" and $Config{'d_unlink_all_versions'}
is "define", then "unlink" will delete all versions of a
file on the first call.)
"unlink" will delete a file if at all possible, even if
it requires changing file protection (though it won't
try to change the protection of the parent directory).
You can tell whether you've got explicit delete access
to a file by using the "VMS::Filespec::candelete"
operator. For instance, in order to delete only files
to which you have delete access, you could say something
like
sub safe_unlink {
my($file,$num);
foreach $file (@_) {
next unless VMS::Filespec::candelete($file);
$num += unlink $file;
}
$num;
}
(or you could just use "VMS::Stdio::remove", if you've
installed the VMS::Stdio extension distributed with
Perl). If "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.
This behavior of "unlink" is to be compatible with POSIX
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behavior and not traditional VMS behavior.
utime LIST
This operator changes only the modification time of the
file (VMS revision date) on ODS-2 volumes and ODS-5
volumes without access dates enabled. On ODS-5 volumes
with access dates enabled, the true access time is
modified.
waitpid PID,FLAGS
If PID is a subprocess started by a piped "open()" (see
open), "waitpid" will wait for that subprocess, and
return its final status value in $?. If PID is a
subprocess created in some other way (e.g. SPAWNed
before Perl was invoked), "waitpid" will simply check
once per second whether the process has completed, and
return when it has. (If PID specifies a process that
isn't a subprocess of the current process, and you
invoked Perl with the "-w" switch, a warning will be
issued.)
Returns PID on success, -1 on error. The FLAGS argument
is ignored in all cases.
Perl variables
The following VMS-specific information applies to the
indicated "special" Perl variables, in addition to the
general information in perlvar. Where there is a conflict,
this information takes precedence.
%ENV
The operation of the %ENV array depends on the
translation of the logical name PERL_ENV_TABLES. If
defined, it should be a search list, each element of
which specifies a location for %ENV elements. If you
tell Perl to read or set the element "$ENV{"name"}",
then Perl uses the translations of PERL_ENV_TABLES as
follows:
CRTL_ENV
This string tells Perl to consult the CRTL's
internal "environ" array of key-value pairs, using
name as the key. In most cases, this contains only
a few keys, but if Perl was invoked via the C
"exec[lv]e()" function, as is the case for CGI
processing by some HTTP servers, then the "environ"
array may have been populated by the calling
program.
CLISYM_[LOCAL]
A string beginning with "CLISYM_"tells Perl to
consult the CLI's symbol tables, using name as the
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name of the symbol. When reading an element of
%ENV, the local symbol table is scanned first,
followed by the global symbol table.. The
characters following "CLISYM_" are significant when
an element of %ENV is set or deleted: if the
complete string is "CLISYM_LOCAL", the change is
made in the local symbol table; otherwise the global
symbol table is changed.
Any other string
If an element of PERL_ENV_TABLES translates to any
other string, that string is used as the name of a
logical name table, which is consulted using name as
the logical name. The normal search order of access
modes is used.
PERL_ENV_TABLES is translated once when Perl starts up;
any changes you make while Perl is running do not affect
the behavior of %ENV. If PERL_ENV_TABLES is not
defined, then Perl defaults to consulting first the
logical name tables specified by LNM$FILE_DEV, and then
the CRTL "environ" array.
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 %ENV is read, the locations to which
PERL_ENV_TABLES points are checked in order, and the
value obtained from the first successful lookup is
returned. If the name of the %ENV element contains a
semi-colon, it and any characters after it are removed.
These are ignored when the CRTL "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 "ONCE UPON A TIME THERE WAS", assuming,
of course, that PERL_ENV_TABLES is set up so that the
logical name "story" is found, rather than a CLI symbol
or CRTL "environ" element with the same name.
When an element of %ENV is set to a defined string, the
corresponding definition is made in the location to
which the first translation of PERL_ENV_TABLES points.
If this causes a logical name to be created, it is
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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
"environ" values; they are set to the empty string.) An
element of the CRTL "environ" array can be set only if
your copy of Perl knows about the CRTL's "setenv()"
function. (This is present only in some versions of the
DECCRTL; check $Config{d_setenv} to see whether your
copy of Perl was built with a CRTL that has this
function.)
When an element of %ENV is set to "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
"environ" array is set to the empty string; this can
only be done if your copy of Perl knows about the CRTL
"setenv()" function.) Using "delete" to remove an
element from %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 $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 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 $ENV{$key} = $ENV{$key}, since the
Perl optimizer is smart enough to elide the expression.)
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Don't try to clear %ENV by saying "%ENV = ();", it will
throw a fatal error. This is equivalent to doing the
following from DCL:
DELETE/LOGICAL *
You can imagine how bad things would be if, for example,
the SYS$MANAGER or SYS$SYSTEM logical names were
deleted.
At present, the first time you iterate over %ENV using
"keys", or "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 logical names
representing process-permanent files, such as
"SYS$INPUT" and "SYS$OUTPUT". The translations for
these logical names are prepended with a two-byte binary
value (0x1B 0x00) that needs to be stripped off if you
wantto use it. (In previous versions of Perl it wasn't
possible to get the values of these logical names, as
the null byte acted as an end-of-string marker)
$! The string value of $! is that returned by the CRTL's
strerror() function, so it will include the VMS message
for VMS-specific errors. The numeric value of $! is the
value of "errno", except if errno is EVMSERR, in which
case $! contains the value of vaxc$errno. Setting $!
always sets errno to the value specified. If this value
is EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-
NOMSG), so that the string value of $! won't reflect the
VMS error message from before $! was set.
$^E This variable provides direct access to VMS status
values in vaxc$errno, which are often more specific than
the generic Unix-style error messages in $!. Its
numeric value is the value of vaxc$errno, and its string
value is the corresponding VMS message string, as
retrieved by sys$getmsg(). Setting $^E sets vaxc$errno
to the value specified.
While Perl attempts to keep the vaxc$errno value to be
current, if errno is not EVMSERR, it may not be from the
current operation.
$? The "status value" returned in $? is synthesized from
the actual exit status of the subprocess in a way that
approximates POSIX wait(5) semantics, in order to allow
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Perl programs to portably test for successful completion
of subprocesses. The low order 8 bits of $? 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 contain the termination status of the
program.
If the child process follows the convention of C
programs compiled with the _POSIX_EXIT macro set, the
status value will contain the actual value of 0 to 255
returned by that program on a normal exit.
With the _POSIX_EXIT macro set, the Unix exit value of
zero is represented as a VMS native status of 1, and the
Unix values from 2 to 255 are encoded by the equation:
VMS_status = 0x35a000 + (unix_value * 8) + 1.
And in the special case of Unix value 1 the encoding is:
VMS_status = 0x35a000 + 8 + 2 + 0x10000000.
For other termination statuses, the severity portion of
the subprocess's exit status is used: if the severity
was success or informational, these bits are all 0; if
the severity was warning, they contain a value of 1; if
the severity was error or fatal error, they contain the
actual severity bits, which turns out to be a value of 2
for error and 4 for severe_error. Fatal is another term
for the severe_error status.
As a result, $? will always be zero if the subprocess's
exit status indicated successful completion, and non-
zero if a warning or error occurred or a program
compliant with encoding _POSIX_EXIT values was run and
set a status.
How can you tell the difference between a non-zero
status that is the result of a VMS native error status
or an encoded Unix status? You can not unless you look
at the ${^CHILD_ERROR_NATIVE} value. The
${^CHILD_ERROR_NATIVE} value returns the actual VMS
status value and check the severity bits. If the
severity bits are equal to 1, then if the numeric value
for $? is between 2 and 255 or 0, then $? accurately
reflects a value passed back from a Unix application.
If $? is 1, and the severity bits indicate a VMS error
(2), then $? is from a Unix application exit value.
In practice, Perl scripts that call programs that return
_POSIX_EXIT type status values will be expecting those
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values, and programs that call traditional VMS programs
will either be expecting the previous behavior or just
checking for a non-zero status.
And success is always the value 0 in all behaviors.
When the actual VMS termination status of the child is
an error, internally the $! value will be set to the
closest Unix errno value to that error so that Perl
scripts that test for error messages will see the
expected Unix style error message instead of a VMS
message.
Conversely, when setting $? in an END block, an attempt
is made to convert the POSIX value into a native status
intelligible to the operating system upon exiting Perl.
What this boils down to is that setting $? to zero
results in the generic success value SS$_NORMAL, and
setting $? to a non-zero value results in the generic
failure status SS$_ABORT. See also "exit" in perlport.
With the "PERL_VMS_POSIX_EXIT" logical name defined as
"ENABLE", setting $? will cause the new value to be
encoded into $^E so that either the original parent or
child exit status values
0 to 255 can be automatically recovered by C programs
expecting _POSIX_EXIT behavior. If both a parent and a
child exit value are non-zero, then it will be assumed
that this is actually a VMS native status value to be
passed through. The special value of 0xFFFF is almost a
NOOP as it will cause the current native VMS status in
the C library to become the current native Perl VMS
status, and is handled this way as it is known to not be
a valid native VMS status value. It is recommend that
only values in the range of normal Unix parent or child
status numbers, 0 to 255 are used.
The pragma "use vmsish 'status'" makes $? reflect the
actual VMS exit status instead of the default emulation
of POSIX status described above. This pragma also
disables the conversion of non-zero values to SS$_ABORT
when setting $? in an END block (but zero will still be
converted to SS$_NORMAL).
Do not use the pragma "use vmsish 'status'" with
"PERL_VMS_POSIX_EXIT" enabled, as they are at times
requesting conflicting actions and the consequence of
ignoring this advice will be undefined to allow future
improvements in the POSIX exit handling.
In general, with "PERL_VMS_POSIX_EXIT" enabled, more
detailed information will be availble in the exit status
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for DCL scripts or other native VMS tools, and will give
the expected information for Posix programs. It has not
been made the default in order to preserve backward
compatibility.
N.B. Setting "DECC$FILENAME_UNIX_REPORT" implicitly
enables "PERL_VMS_POSIX_EXIT".
$| Setting $| for an I/O stream causes data to be flushed
all the way to disk on each write (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.
Standard modules with VMS-specific differences
SDBM_File
SDBM_File works properly on VMS. It has, however, one minor
difference. The database directory file created has a
.sdbm_dir extension rather than a .dir extension. .dir files
are VMS filesystem directory files, and using them for other
purposes could cause unacceptable problems.
Revision date
Please see the git repository for revision history.
AUTHOR
Charles Bailey bailey@cor.newman.upenn.edu Craig Berry
craigberry@mac.com Dan Sugalski dan@sidhe.org John Malmberg
wb8tyw@qsl.net
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.perl.org/.
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