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.\" ========================================================================
.\"
.IX Title "PERLVMS 1"
.TH PERLVMS 1 "2002-11-24" "perl v5.8.0" "Perl Programmers Reference Guide"
.SH "NAME"
perlvms \- VMS\-specific documentation for Perl
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Gathered below are notes describing details of Perl 5's
behavior on \s-1VMS\s0. They are a supplement to the regular Perl 5
documentation, so we have focussed on the ways in which Perl
5 functions differently under \s-1VMS\s0 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 \fI[.pod]\fR
subdirectory of the Perl distribution.
.PP
We hope these notes will save you from confusion and lost
sleep when writing Perl scripts on \s-1VMS\s0. If you find we've
missed something you think should appear here, please don't
hesitate to drop a line to vmsperl@perl.org.
.SH "Installation"
.IX Header "Installation"
Directions for building and installing Perl 5 can be found in
the file \fI\s-1README\s0.vms\fR in the main source directory of the
Perl distribution..
.SH "Organization of Perl Images"
.IX Header "Organization of Perl Images"
.Sh "Core Images"
.IX Subsection "Core Images"
During the installation process, three Perl images are produced.
\&\fIMiniperl.Exe\fR 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.
.PP
Most of the complete Perl resides in the shareable image
\&\fIPerlShr.Exe\fR, which provides a core to which the Perl executable
image and all Perl extensions are linked. You should place this
image in \fISys$Share\fR, or define the logical name \fIPerlShr\fR 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 \fIPerlShr\fR, \s-1VMS\s0 will treat it as if it were a privileged shareable
image, and will therefore require all downstream shareable images to be
INSTALLed, etc.)
.PP
Finally, \fIPerl.Exe\fR 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.
.Sh "Perl Extensions"
.IX Subsection "Perl Extensions"
Perl extensions are packages which provide both \s-1XS\s0 and Perl code
to add new functionality to perl. (\s-1XS\s0 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
\&\f(CW\*(C`use\*(C'\fR or \f(CW\*(C`require\*(C'\fR statement, and usually defines a Perl
package containing the extension.
.PP
The portion of the extension provided by the \s-1XS\s0 code may be
connected to the rest of Perl in either of two ways. In the
\&\fBstatic\fR configuration, the object code for the extension is
linked directly into \fIPerlShr.Exe\fR, and is initialized whenever
Perl is invoked. In the \fBdynamic\fR configuration, the extension's
machine code is placed into a separate shareable image, which is
mapped by Perl's DynaLoader when the extension is \f(CW\*(C`use\*(C'\fRd or
\&\f(CW\*(C`require\*(C'\fRd 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.
.PP
The source code for an extension usually resides in its own
directory. At least three files are generally provided:
\&\fIExtshortname\fR\fI.xs\fR (where \fIExtshortname\fR is the portion of
the extension's name following the last \f(CW\*(C`::\*(C'\fR), containing
the \s-1XS\s0 code, \fIExtshortname\fR\fI.pm\fR, the Perl library module
for the extension, and \fIMakefile.PL\fR, a Perl script which uses
the \f(CW\*(C`MakeMaker\*(C'\fR library modules supplied with Perl to generate
a \fIDescrip.MMS\fR file for the extension.
.Sh "Installing static extensions"
.IX Subsection "Installing static extensions"
Since static extensions are incorporated directly into
\&\fIPerlShr.Exe\fR, you'll have to rebuild Perl to incorporate a
new extension. You should edit the main \fIDescrip.MMS\fR or \fIMakefile\fR
you use to build Perl, adding the extension's name to the \f(CW\*(C`ext\*(C'\fR
macro, and the extension's object file to the \f(CW\*(C`extobj\*(C'\fR macro.
You'll also need to build the extension's object file, either
by adding dependencies to the main \fIDescrip.MMS\fR, or using a
separate \fIDescrip.MMS\fR for the extension. Then, rebuild
\&\fIPerlShr.Exe\fR to incorporate the new code.
.PP
Finally, you'll need to copy the extension's Perl library
module to the \fI[.\fR\fIExtname\fR\fI]\fR subdirectory under one
of the directories in \f(CW@INC\fR, where \fIExtname\fR is the name
of the extension, with all \f(CW\*(C`::\*(C'\fR replaced by \f(CW\*(C`.\*(C'\fR (e.g.
the library module for extension Foo::Bar would be copied
to a \fI[.Foo.Bar]\fR subdirectory).
.Sh "Installing dynamic extensions"
.IX Subsection "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 \fIDescrip.MMS\fR file which can be used to build and
install the files required by the extension. The kit should be
unpacked into a directory tree \fBnot\fR under the main Perl source
directory, and the procedure for building the extension is simply
.PP
.Vb 4
\& $ perl Makefile.PL ! Create Descrip.MMS
\& $ mmk ! Build necessary files
\& $ mmk test ! Run test code, if supplied
\& $ mmk install ! Install into public Perl tree
.Ve
.PP
\&\fIN.B.\fR 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 exceed \s-1RMS\s0'
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.)
.PP
\&\s-1VMS\s0 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 \fI\s-1PGPLOT\s0\fR extension to Perl requires the
\&\fI\s-1PGPLOTSHR\s0.EXE\fR shareable image in order to properly link
the Perl extension, then the line \f(CW\*(C`PGPLOTSHR/Share\*(C'\fR must
be added to the linker options file \fI\s-1PGPLOT\s0.Opt\fR produced
during the build process for the Perl extension.
.PP
By default, the shareable image for an extension is placed
\&\fI[.lib.site_perl.auto\fR\fIArch\fR.\fIExtname\fR\fI]\fR directory of the
installed Perl directory tree (where \fIArch\fR is \fI\s-1VMS_VAX\s0\fR or
\&\fI\s-1VMS_AXP\s0\fR, and \fIExtname\fR is the name of the extension, with
each \f(CW\*(C`::\*(C'\fR translated to \f(CW\*(C`.\*(C'\fR). (See the MakeMaker documentation
for more details on installation options for extensions.)
However, it can be manually placed in any of several locations:
\- the \fI[.Lib.Auto.\fR\fIArch\fR\fI$PVers\fR\fIExtname\fR\fI]\fR subdirectory
of one of the directories in \f(CW@INC\fR (where \fIPVers\fR
is the version of Perl you're using, as supplied in \f(CW$]\fR,
with '.' converted to '_'), or
\- one of the directories in \f(CW@INC\fR, or
\- a directory which the extensions Perl library module
passes to the DynaLoader when asking it to map
the shareable image, or
\- \fISys$Share\fR or \fISys$Library\fR.
If the shareable image isn't in any of these places, you'll need
to define a logical name \fIExtshortname\fR, where \fIExtshortname\fR
is the portion of the extension's name after the last \f(CW\*(C`::\*(C'\fR, which
translates to the full file specification of the shareable image.
.SH "File specifications"
.IX Header "File specifications"
.Sh "Syntax"
.IX Subsection "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. \s-1VMS\s0 Perl interprets Unix pathnames in much
the same way as the \s-1CRTL\s0 (\fIe.g.\fR the first component of
an absolute path is read as the device name for the
\&\s-1VMS\s0 file specification). There are a set of functions
provided in the \f(CW\*(C`VMS::Filespec\*(C'\fR package for explicit
interconversion between \s-1VMS\s0 and Unix syntax; its
documentation provides more details.
.PP
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 \s-1VMS\s0; Perl respects the case-sensitivity
of OSs like Unix.)
.PP
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, \fIetc.\fR If you find instances
of this in the Perl distribution itself, please let us know,
so we can try to work around them.
.Sh "Wildcard expansion"
.IX Subsection "Wildcard expansion"
File specifications containing wildcards are allowed both on
the command line and within Perl globs (e.g. \f(CW\*(C`<*.c>\*(C'\fR). If
the wildcard filespec uses \s-1VMS\s0 syntax, the resultant
filespecs will follow \s-1VMS\s0 syntax; if a Unix-style filespec is
passed in, Unix-style filespecs will be returned.
.PP
In both cases, \s-1VMS\s0 wildcard expansion is performed. (csh\-style
wildcard expansion is available if you use \f(CW\*(C`File::Glob::glob\*(C'\fR.)
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 \f(CW\*(C`[.t]*.*\*(C'\fR will yield filespecs like
\&\*(L"perl_root:[t]base.dir\*(R", while the expansion of \f(CW\*(C`t/*/*\*(C'\fR will
yield filespecs like \*(L"t/base.dir\*(R". (This is done to match
the behavior of glob expansion performed by Unix shells.)
.PP
Similarly, the resultant filespec will contain the file version
only if one was present in the input filespec.
.Sh "Pipes"
.IX Subsection "Pipes"
Input and output pipes to Perl filehandles are supported; the
\&\*(L"file name\*(R" is passed to lib$\fIspawn()\fR for asynchronous
execution. You should be careful to close any pipes you have
opened in a Perl script, lest you leave any \*(L"orphaned\*(R"
subprocesses around when Perl exits.
.PP
You may also use backticks to invoke a \s-1DCL\s0 subprocess, whose
output is used as the return value of the expression. The
string between the backticks is handled as if it were the
argument to the \f(CW\*(C`system\*(C'\fR operator (see below). In this case,
Perl will wait for the subprocess to complete before continuing.
.PP
The mailbox (\s-1MBX\s0) that perl can create to communicate with a pipe
defaults to a buffer size of 512. The default buffer size is
adjustable via the logical name \s-1PERL_MBX_SIZE\s0 provided that the
value falls between 128 and the \s-1SYSGEN\s0 parameter \s-1MAXBUF\s0 inclusive.
For example, to double the \s-1MBX\s0 size from the default within
a Perl program, use \f(CW\*(C`$ENV{'PERL_MBX_SIZE'} = 1024;\*(C'\fR and then
open and use pipe constructs. An alternative would be to issue
the command:
.PP
.Vb 1
\& $ Define PERL_MBX_SIZE 1024
.Ve
.PP
before running your wide record pipe program. A larger value may
improve performance at the expense of the \s-1BYTLM\s0 \s-1UAF\s0 quota.
.SH "PERL5LIB and PERLLIB"
.IX Header "PERL5LIB and PERLLIB"
The \s-1PERL5LIB\s0 and \s-1PERLLIB\s0 logical names work as documented in perl,
except that the element separator is '|' instead of ':'. The
directory specifications may use either \s-1VMS\s0 or Unix syntax.
.SH "Command line"
.IX Header "Command line"
.Sh "I/O redirection and backgrounding"
.IX Subsection "I/O redirection and backgrounding"
Perl for \s-1VMS\s0 supports redirection of input and output on the
command line, using a subset of Bourne shell syntax:
.IP "\(bu" 4
\&\f(CW\*(C`<file\*(C'\fR reads stdin from \f(CW\*(C`file\*(C'\fR,
.IP "\(bu" 4
\&\f(CW\*(C`>file\*(C'\fR writes stdout to \f(CW\*(C`file\*(C'\fR,
.IP "\(bu" 4
\&\f(CW\*(C`>>file\*(C'\fR appends stdout to \f(CW\*(C`file\*(C'\fR,
.IP "\(bu" 4
\&\f(CW\*(C`2>file\*(C'\fR writes stderr to \f(CW\*(C`file\*(C'\fR, and
.IP "\(bu" 4
\&\f(CW\*(C`2>>file\*(C'\fR appends stderr to \f(CW\*(C`file\*(C'\fR.
.PP
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.
.PP
Finally, if the command line ends with '&', the entire
command is run in the background as an asynchronous
subprocess.
.Sh "Command line switches"
.IX Subsection "Command line switches"
The following command line switches behave differently under
\&\s-1VMS\s0 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 \s-1CRTL\s0
downcases all unquoted strings.
.IP "\-i" 4
.IX Item "-i"
If the \f(CW\*(C`\-i\*(C'\fR 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.)
.IP "\-S" 4
.IX Item "-S"
If the \f(CW"\-S"\fR or \f(CW\*(C`\-"S"\*(C'\fR switch is present \fIand\fR the script
name does not contain a directory, then Perl translates the
logical name \s-1DCL$PATH\s0 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 \fI.pl\fR, and a type of \fI.com\fR, in that order.
.IP "\-u" 4
.IX Item "-u"
The \f(CW\*(C`\-u\*(C'\fR switch causes the \s-1VMS\s0 debugger to be invoked
after the Perl program is compiled, but before it has
run. It does not create a core dump file.
.SH "Perl functions"
.IX Header "Perl functions"
As of the time this document was last revised, the following
Perl functions were implemented in the \s-1VMS\s0 port of Perl
(functions marked with * are discussed in more detail below):
.PP
.Vb 19
\& 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, endpwent, eof, eval, exec*,
\& exists, exit, exp, fileno, getc, getlogin, getppid,
\& 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),
\& 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///
.Ve
.PP
The following functions were not implemented in the \s-1VMS\s0 port,
and calling them produces a fatal error (usually) or
undefined behavior (rarely, we hope):
.PP
.Vb 6
\& chroot, dbmclose, dbmopen, flock, fork*,
\& getpgrp, 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
.Ve
.PP
The following functions are available on Perls compiled with Dec C
5.2 or greater and running \s-1VMS\s0 7.0 or greater:
.PP
.Vb 1
\& truncate
.Ve
.PP
The following functions are available on Perls built on \s-1VMS\s0 7.2 or
greater:
.PP
.Vb 1
\& fcntl (without locking)
.Ve
.PP
The following functions may or may not be implemented,
depending on what type of socket support you've built into
your copy of Perl:
.PP
.Vb 9
\& 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
.Ve
.IP "File tests" 4
.IX Item "File tests"
The tests \f(CW\*(C`\-b\*(C'\fR, \f(CW\*(C`\-B\*(C'\fR, \f(CW\*(C`\-c\*(C'\fR, \f(CW\*(C`\-C\*(C'\fR, \f(CW\*(C`\-d\*(C'\fR, \f(CW\*(C`\-e\*(C'\fR, \f(CW\*(C`\-f\*(C'\fR,
\&\f(CW\*(C`\-o\*(C'\fR, \f(CW\*(C`\-M\*(C'\fR, \f(CW\*(C`\-s\*(C'\fR, \f(CW\*(C`\-S\*(C'\fR, \f(CW\*(C`\-t\*(C'\fR, \f(CW\*(C`\-T\*(C'\fR, and \f(CW\*(C`\-z\*(C'\fR work as
advertised. The return values for \f(CW\*(C`\-r\*(C'\fR, \f(CW\*(C`\-w\*(C'\fR, and \f(CW\*(C`\-x\*(C'\fR
tell you whether you can actually access the file; this may
not reflect the UIC-based file protections. Since real and
effective \s-1UIC\s0 don't differ under \s-1VMS\s0, \f(CW\*(C`\-O\*(C'\fR, \f(CW\*(C`\-R\*(C'\fR, \f(CW\*(C`\-W\*(C'\fR,
and \f(CW\*(C`\-X\*(C'\fR are equivalent to \f(CW\*(C`\-o\*(C'\fR, \f(CW\*(C`\-r\*(C'\fR, \f(CW\*(C`\-w\*(C'\fR, and \f(CW\*(C`\-x\*(C'\fR.
Similarly, several other tests, including \f(CW\*(C`\-A\*(C'\fR, \f(CW\*(C`\-g\*(C'\fR, \f(CW\*(C`\-k\*(C'\fR,
\&\f(CW\*(C`\-l\*(C'\fR, \f(CW\*(C`\-p\*(C'\fR, and \f(CW\*(C`\-u\*(C'\fR, aren't particularly meaningful under
\&\s-1VMS\s0, and the values returned by these tests reflect whatever
your \s-1CRTL\s0 \f(CW\*(C`stat()\*(C'\fR routine does to the equivalent bits in the
st_mode field. Finally, \f(CW\*(C`\-d\*(C'\fR returns true if passed a device
specification without an explicit directory (e.g. \f(CW\*(C`DUA1:\*(C'\fR), as
well as if passed a directory.
.Sp
Note: Some sites have reported problems when using the file-access
tests (\f(CW\*(C`\-r\*(C'\fR, \f(CW\*(C`\-w\*(C'\fR, and \f(CW\*(C`\-x\*(C'\fR) on files accessed via \s-1DEC\s0's \s-1DFS\s0.
Specifically, since \s-1DFS\s0 does not currently provide access to the
extended file header of files on remote volumes, attempts to
examine the \s-1ACL\s0 fail, and the file tests will return false,
with \f(CW$!\fR indicating that the file does not exist. You can
use \f(CW\*(C`stat\*(C'\fR on these files, since that checks UIC-based protection
only, and then manually check the appropriate bits, as defined by
your C compiler's \fIstat.h\fR, in the mode value it returns, if you
need an approximation of the file's protections.
.IP "backticks" 4
.IX Item "backticks"
Backticks create a subprocess, and pass the enclosed string
to it for execution as a \s-1DCL\s0 command. Since the subprocess is
created directly via \f(CW\*(C`lib$spawn()\*(C'\fR, any valid \s-1DCL\s0 command string
may be specified.
.IP "binmode \s-1FILEHANDLE\s0" 4
.IX Item "binmode FILEHANDLE"
The \f(CW\*(C`binmode\*(C'\fR operator will attempt to insure that no translation
of carriage control occurs on input from or output to this filehandle.
Since this involves reopening the file and then restoring its
file position indicator, if this function returns \s-1FALSE\s0, the
underlying filehandle may no longer point to an open file, or may
point to a different position in the file than before \f(CW\*(C`binmode\*(C'\fR
was called.
.Sp
Note that \f(CW\*(C`binmode\*(C'\fR is generally not necessary when using normal
filehandles; it is provided so that you can control I/O to existing
record-structured files when necessary. You can also use the
\&\f(CW\*(C`vmsfopen\*(C'\fR function in the VMS::Stdio extension to gain finer
control of I/O to files and devices with different record structures.
.IP "crypt \s-1PLAINTEXT\s0, \s-1USER\s0" 4
.IX Item "crypt PLAINTEXT, USER"
The \f(CW\*(C`crypt\*(C'\fR operator uses the \f(CW\*(C`sys$hash_password\*(C'\fR system
service to generate the hashed representation of \s-1PLAINTEXT\s0.
If \s-1USER\s0 is a valid username, the algorithm and salt values
are taken from that user's \s-1UAF\s0 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.
.Sp
The value returned by \f(CW\*(C`crypt\*(C'\fR may be compared against
the encrypted password from the \s-1UAF\s0 returned by the \f(CW\*(C`getpw*\*(C'\fR
functions, in order to authenticate users. If you're
going to do this, remember that the encrypted password in
the \s-1UAF\s0 was generated using uppercase username and
password strings; you'll have to upcase the arguments to
\&\f(CW\*(C`crypt\*(C'\fR to insure that you'll get the proper value:
.Sp
.Vb 9
\& sub validate_passwd {
\& my($user,$passwd) = @_;
\& my($pwdhash);
\& if ( !($pwdhash = (getpwnam($user))[1]) ||
\& $pwdhash ne crypt("\eU$passwd","\eU$name") ) {
\& intruder_alert($name);
\& }
\& return 1;
\& }
.Ve
.IP "dump" 4
.IX Item "dump"
Rather than causing Perl to abort and dump core, the \f(CW\*(C`dump\*(C'\fR
operator invokes the \s-1VMS\s0 debugger. If you continue to
execute the Perl program under the debugger, control will
be transferred to the label specified as the argument to
\&\f(CW\*(C`dump\*(C'\fR, or, if no label was specified, back to the
beginning of the program. All other state of the program
(\fIe.g.\fR values of variables, open file handles) are not
affected by calling \f(CW\*(C`dump\*(C'\fR.
.IP "exec \s-1LIST\s0" 4
.IX Item "exec LIST"
A call to \f(CW\*(C`exec\*(C'\fR will cause Perl to exit, and to invoke the command
given as an argument to \f(CW\*(C`exec\*(C'\fR via \f(CW\*(C`lib$do_command\*(C'\fR. If the
argument begins with '@' or '$' (other than as part of a filespec),
then it is executed as a \s-1DCL\s0 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 \fI.Exe\fR and the process
defaults to expand the filespec) and pass the rest of \f(CW\*(C`exec\*(C'\fR'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 \f(CW\*(C`MCR\*(C'\fR or a text file which should be passed to \s-1DCL\s0 as a
command procedure.
.IP "fork" 4
.IX Item "fork"
While in principle the \f(CW\*(C`fork\*(C'\fR operator could be implemented via
(and with the same rather severe limitations as) the \s-1CRTL\s0 \f(CW\*(C`vfork()\*(C'\fR
routine, and while some internal support to do just that is in
place, the implementation has never been completed, making \f(CW\*(C`fork\*(C'\fR
currently unavailable. A true kernel \f(CW\*(C`fork()\*(C'\fR is expected in a
future version of \s-1VMS\s0, and the pseudo-fork based on interpreter
threads may be available in a future version of Perl on \s-1VMS\s0 (see
perlfork). In the meantime, use \f(CW\*(C`system\*(C'\fR, backticks, or piped
filehandles to create subprocesses.
.IP "getpwent" 4
.IX Item "getpwent"
.PD 0
.IP "getpwnam" 4
.IX Item "getpwnam"
.IP "getpwuid" 4
.IX Item "getpwuid"
.PD
These operators obtain the information described in perlfunc,
if you have the privileges necessary to retrieve the named user's
\&\s-1UAF\s0 information via \f(CW\*(C`sys$getuai\*(C'\fR. If not, then only the \f(CW$name\fR,
\&\f(CW$uid\fR, and \f(CW$gid\fR items are returned. The \f(CW$dir\fR item contains
the login directory in \s-1VMS\s0 syntax, while the \f(CW$comment\fR item
contains the login directory in Unix syntax. The \f(CW$gcos\fR item
contains the owner field from the \s-1UAF\s0 record. The \f(CW$quota\fR
item is not used.
.IP "gmtime" 4
.IX Item "gmtime"
The \f(CW\*(C`gmtime\*(C'\fR operator will function properly if you have a
working \s-1CRTL\s0 \f(CW\*(C`gmtime()\*(C'\fR routine, or if the logical name
\&\s-1SYS$TIMEZONE_DIFFERENTIAL\s0 is defined as the number of seconds
which must be added to \s-1UTC\s0 to yield local time. (This logical
name is defined automatically if you are running a version of
\&\s-1VMS\s0 with built-in \s-1UTC\s0 support.) If neither of these cases is
true, a warning message is printed, and \f(CW\*(C`undef\*(C'\fR is returned.
.IP "kill" 4
.IX Item "kill"
In most cases, \f(CW\*(C`kill\*(C'\fR is implemented via the \s-1CRTL\s0's \f(CW\*(C`kill()\*(C'\fR
function, so it will behave according to that function's
documentation. If you send a \s-1SIGKILL\s0, however, the \f(CW$DELPRC\fR system
service is called directly. This insures that the target
process is actually deleted, if at all possible. (The \s-1CRTL\s0's \f(CW\*(C`kill()\*(C'\fR
function is presently implemented via \f(CW$FORCEX\fR, which is ignored by
supervisor-mode images like \s-1DCL\s0.)
.Sp
Also, negative signal values don't do anything special under
\&\s-1VMS\s0; they're just converted to the corresponding positive value.
.IP "qx//" 4
.IX Item "qx//"
See the entry on \f(CW\*(C`backticks\*(C'\fR above.
.IP "select (system call)" 4
.IX Item "select (system call)"
If Perl was not built with socket support, the system call
version of \f(CW\*(C`select\*(C'\fR is not available at all. If socket
support is present, then the system call version of
\&\f(CW\*(C`select\*(C'\fR functions only for file descriptors attached
to sockets. It will not provide information about regular
files or pipes, since the \s-1CRTL\s0 \f(CW\*(C`select()\*(C'\fR routine does not
provide this functionality.
.IP "stat \s-1EXPR\s0" 4
.IX Item "stat EXPR"
Since \s-1VMS\s0 keeps track of files according to a different scheme
than Unix, it's not really possible to represent the file's \s-1ID\s0
in the \f(CW\*(C`st_dev\*(C'\fR and \f(CW\*(C`st_ino\*(C'\fR fields of a \f(CW\*(C`struct stat\*(C'\fR. Perl
tries its best, though, and the values it uses are pretty unlikely
to be the same for two different files. We can't guarantee this,
though, so caveat scriptor.
.IP "system \s-1LIST\s0" 4
.IX Item "system LIST"
The \f(CW\*(C`system\*(C'\fR operator creates a subprocess, and passes its
arguments to the subprocess for execution as a \s-1DCL\s0 command.
Since the subprocess is created directly via \f(CW\*(C`lib$spawn()\*(C'\fR, any
valid \s-1DCL\s0 command string may be specified. If the string begins with
\&'@', it is treated as a \s-1DCL\s0 command unconditionally. Otherwise, if
the first token contains a character used as a delimiter in file
specification (e.g. \f(CW\*(C`:\*(C'\fR or \f(CW\*(C`]\*(C'\fR), an attempt is made to expand it
using a default type of \fI.Exe\fR and the process defaults, and if
successful, the resulting file is invoked via \f(CW\*(C`MCR\*(C'\fR. This allows you
to invoke an image directly simply by passing the file specification
to \f(CW\*(C`system\*(C'\fR, 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 \f(CW\*(C`MCR\*(C'\fR or a text file which should be passed to \s-1DCL\s0
as a command procedure.
.Sp
If \s-1LIST\s0 consists of the empty string, \f(CW\*(C`system\*(C'\fR spawns an
interactive \s-1DCL\s0 subprocess, in the same fashion as typing
\&\fB\s-1SPAWN\s0\fR at the \s-1DCL\s0 prompt.
.Sp
Perl waits for the subprocess to complete before continuing
execution in the current process. As described in perlfunc,
the return value of \f(CW\*(C`system\*(C'\fR is a fake \*(L"status\*(R" which follows
\&\s-1POSIX\s0 semantics unless the pragma \f(CW\*(C`use vmsish 'status'\*(C'\fR is in
effect; see the description of \f(CW$?\fR in this document for more
detail.
.IP "time" 4
.IX Item "time"
The value returned by \f(CW\*(C`time\*(C'\fR is the offset in seconds from
01\-JAN\-1970 00:00:00 (just like the \s-1CRTL\s0's \fItimes()\fR routine), in order
to make life easier for code coming in from the POSIX/Unix world.
.IP "times" 4
.IX Item "times"
The array returned by the \f(CW\*(C`times\*(C'\fR operator is divided up
according to the same rules the \s-1CRTL\s0 \f(CW\*(C`times()\*(C'\fR routine.
Therefore, the \*(L"system time\*(R" elements will always be 0, since
there is no difference between \*(L"user time\*(R" and \*(L"system\*(R" time
under \s-1VMS\s0, and the time accumulated by a subprocess may or may
not appear separately in the \*(L"child time\*(R" field, depending on
whether times keeps track of subprocesses separately. Note
especially that the \s-1VAXCRTL\s0 (at least) keeps track only of
subprocesses spawned using fork and exec; it will not
accumulate the times of subprocesses spawned via pipes, system,
or backticks.
.IP "unlink \s-1LIST\s0" 4
.IX Item "unlink LIST"
\&\f(CW\*(C`unlink\*(C'\fR will delete the highest version of a file only; in
order to delete all versions, you need to say
.Sp
.Vb 1
\& 1 while unlink LIST;
.Ve
.Sp
You may need to make this change to scripts written for a
Unix system which expect that after a call to \f(CW\*(C`unlink\*(C'\fR,
no files with the names passed to \f(CW\*(C`unlink\*(C'\fR will exist.
(Note: This can be changed at compile time; if you
\&\f(CW\*(C`use Config\*(C'\fR and \f(CW$Config{'d_unlink_all_versions'}\fR is
\&\f(CW\*(C`define\*(C'\fR, then \f(CW\*(C`unlink\*(C'\fR will delete all versions of a
file on the first call.)
.Sp
\&\f(CW\*(C`unlink\*(C'\fR 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
\&\f(CW\*(C`VMS::Filespec::candelete\*(C'\fR operator. For instance, in order
to delete only files to which you have delete access, you could
say something like
.Sp
.Vb 8
\& sub safe_unlink {
\& my($file,$num);
\& foreach $file (@_) {
\& next unless VMS::Filespec::candelete($file);
\& $num += unlink $file;
\& }
\& $num;
\& }
.Ve
.Sp
(or you could just use \f(CW\*(C`VMS::Stdio::remove\*(C'\fR, if you've installed
the VMS::Stdio extension distributed with Perl). If \f(CW\*(C`unlink\*(C'\fR has to
change the file protection to delete the file, and you interrupt it
in midstream, the file may be left intact, but with a changed \s-1ACL\s0
allowing you delete access.
.IP "utime \s-1LIST\s0" 4
.IX Item "utime LIST"
Since \s-1ODS\-2\s0, the \s-1VMS\s0 file structure for disk files, does not keep
track of access times, this operator changes only the modification
time of the file (\s-1VMS\s0 revision date).
.IP "waitpid \s-1PID\s0,FLAGS" 4
.IX Item "waitpid PID,FLAGS"
If \s-1PID\s0 is a subprocess started by a piped \f(CW\*(C`open()\*(C'\fR (see open),
\&\f(CW\*(C`waitpid\*(C'\fR will wait for that subprocess, and return its final status
value in \f(CW$?\fR. If \s-1PID\s0 is a subprocess created in some other way (e.g.
SPAWNed before Perl was invoked), \f(CW\*(C`waitpid\*(C'\fR will simply check once per
second whether the process has completed, and return when it has. (If
\&\s-1PID\s0 specifies a process that isn't a subprocess of the current process,
and you invoked Perl with the \f(CW\*(C`\-w\*(C'\fR switch, a warning will be issued.)
.Sp
Returns \s-1PID\s0 on success, \-1 on error. The \s-1FLAGS\s0 argument is ignored
in all cases.
.SH "Perl variables"
.IX Header "Perl variables"
The following VMS-specific information applies to the indicated
\&\*(L"special\*(R" Perl variables, in addition to the general information
in perlvar. Where there is a conflict, this information
takes precedence.
.IP "%ENV" 4
.IX Item "%ENV"
The operation of the \f(CW%ENV\fR array depends on the translation
of the logical name \fI\s-1PERL_ENV_TABLES\s0\fR. If defined, it should
be a search list, each element of which specifies a location
for \f(CW%ENV\fR elements. If you tell Perl to read or set the
element \f(CW\*(C`$ENV{\*(C'\fR\fIname\fR\f(CW\*(C`}\*(C'\fR, then Perl uses the translations of
\&\fI\s-1PERL_ENV_TABLES\s0\fR as follows:
.RS 4
.IP "\s-1CRTL_ENV\s0" 4
.IX Item "CRTL_ENV"
This string tells Perl to consult the \s-1CRTL\s0's internal \f(CW\*(C`environ\*(C'\fR
array of key-value pairs, using \fIname\fR as the key. In most cases,
this contains only a few keys, but if Perl was invoked via the C
\&\f(CW\*(C`exec[lv]e()\*(C'\fR function, as is the case for \s-1CGI\s0 processing by some
\&\s-1HTTP\s0 servers, then the \f(CW\*(C`environ\*(C'\fR array may have been populated by
the calling program.
.IP "CLISYM_[\s-1LOCAL\s0]" 4
.IX Item "CLISYM_[LOCAL]"
A string beginning with \f(CW\*(C`CLISYM_\*(C'\fRtells Perl to consult the \s-1CLI\s0's
symbol tables, using \fIname\fR as the name of the symbol. When reading
an element of \f(CW%ENV\fR, the local symbol table is scanned first, followed
by the global symbol table.. The characters following \f(CW\*(C`CLISYM_\*(C'\fR are
significant when an element of \f(CW%ENV\fR is set or deleted: if the
complete string is \f(CW\*(C`CLISYM_LOCAL\*(C'\fR, the change is made in the local
symbol table; otherwise the global symbol table is changed.
.IP "Any other string" 4
.IX Item "Any other string"
If an element of \fI\s-1PERL_ENV_TABLES\s0\fR translates to any other string,
that string is used as the name of a logical name table, which is
consulted using \fIname\fR as the logical name. The normal search
order of access modes is used.
.RE
.RS 4
.Sp
\&\fI\s-1PERL_ENV_TABLES\s0\fR is translated once when Perl starts up; any changes
you make while Perl is running do not affect the behavior of \f(CW%ENV\fR.
If \fI\s-1PERL_ENV_TABLES\s0\fR is not defined, then Perl defaults to consulting
first the logical name tables specified by \fI\s-1LNM$FILE_DEV\s0\fR, and then
the \s-1CRTL\s0 \f(CW\*(C`environ\*(C'\fR array.
.Sp
In all operations on \f(CW%ENV\fR, the key string is treated as if it
were entirely uppercase, regardless of the case actually
specified in the Perl expression.
.Sp
When an element of \f(CW%ENV\fR is read, the locations to which
\&\fI\s-1PERL_ENV_TABLES\s0\fR points are checked in order, and the value
obtained from the first successful lookup is returned. If the
name of the \f(CW%ENV\fR element contains a semi\-colon, it and
any characters after it are removed. These are ignored when
the \s-1CRTL\s0 \f(CW\*(C`environ\*(C'\fR array or a \s-1CLI\s0 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
.Sp
.Vb 3
\& $ Define STORY once,upon,a,time,there,was
\& $ perl -e "for ($i = 0; $i <= 6; $i++) " -
\& _$ -e "{ print $ENV{'story;'.$i},' '}"
.Ve
.Sp
Perl will print \f(CW\*(C`ONCE UPON A TIME THERE WAS\*(C'\fR, assuming, of course,
that \fI\s-1PERL_ENV_TABLES\s0\fR is set up so that the logical name \f(CW\*(C`story\*(C'\fR
is found, rather than a \s-1CLI\s0 symbol or \s-1CRTL\s0 \f(CW\*(C`environ\*(C'\fR element with
the same name.
.Sp
When an element of \f(CW%ENV\fR is set to a defined string, the
corresponding definition is made in the location to which the
first translation of \fI\s-1PERL_ENV_TABLES\s0\fR 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 \s-1NUL\s0
(\s-1ASCII\s0 00) character, since a logical name cannot translate to a
zero-length string. (This restriction does not apply to \s-1CLI\s0 symbols
or \s-1CRTL\s0 \f(CW\*(C`environ\*(C'\fR values; they are set to the empty string.)
An element of the \s-1CRTL\s0 \f(CW\*(C`environ\*(C'\fR array can be set only if your
copy of Perl knows about the \s-1CRTL\s0's \f(CW\*(C`setenv()\*(C'\fR function. (This is
present only in some versions of the \s-1DECCRTL\s0; check \f(CW$Config{d_setenv}\fR
to see whether your copy of Perl was built with a \s-1CRTL\s0 that has this
function.)
.Sp
When an element of \f(CW%ENV\fR is set to \f(CW\*(C`undef\*(C'\fR,
the element is looked up as if it were being read, and if it is
found, it is deleted. (An item \*(L"deleted\*(R" from the \s-1CRTL\s0 \f(CW\*(C`environ\*(C'\fR
array is set to the empty string; this can only be done if your
copy of Perl knows about the \s-1CRTL\s0 \f(CW\*(C`setenv()\*(C'\fR function.) Using
\&\f(CW\*(C`delete\*(C'\fR to remove an element from \f(CW%ENV\fR has a similar effect,
but after the element is deleted, another attempt is made to
look up the element, so an inner-mode logical name or a name in
another location will replace the logical name just deleted.
In either case, only the first value found searching \s-1PERL_ENV_TABLES\s0
is altered. It is not possible at present to define a search list
logical name via \f(CW%ENV\fR.
.Sp
The element \f(CW$ENV{DEFAULT}\fR is special: when read, it returns
Perl's current default device and directory, and when set, it
resets them, regardless of the definition of \fI\s-1PERL_ENV_TABLES\s0\fR.
It cannot be cleared or deleted; attempts to do so are silently
ignored.
.Sp
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 \*(L"promote\*(R" them to logical names in the current
process, which will then be inherited by all subprocesses,
by saying
.Sp
.Vb 4
\& foreach my $key (qw[C-local keys you want promoted]) {
\& my $temp = $ENV{$key}; # read from C-local array
\& $ENV{$key} = $temp; # and define as logical name
\& }
.Ve
.Sp
(You can't just say \f(CW$ENV{$key} = $ENV{$key}\fR, since the
Perl optimizer is smart enough to elide the expression.)
.Sp
Don't try to clear \f(CW%ENV\fR by saying \f(CW\*(C`%ENV = ();\*(C'\fR, it will throw
a fatal error. This is equivalent to doing the following from \s-1DCL:\s0
.Sp
.Vb 1
\& DELETE/LOGICAL *
.Ve
.Sp
You can imagine how bad things would be if, for example, the \s-1SYS$MANAGER\s0
or \s-1SYS$SYSTEM\s0 logicals were deleted.
.Sp
At present, the first time you iterate over \f(CW%ENV\fR using
\&\f(CW\*(C`keys\*(C'\fR, or \f(CW\*(C`values\*(C'\fR, you will incur a time penalty as all
logical names are read, in order to fully populate \f(CW%ENV\fR.
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.
.Sp
You do need to be careful with the logicals representing process-permanent
files, such as \f(CW\*(C`SYS$INPUT\*(C'\fR and \f(CW\*(C`SYS$OUTPUT\*(C'\fR. 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)
.RE
.IP "$!" 4
The string value of \f(CW$!\fR is that returned by the \s-1CRTL\s0's
\&\fIstrerror()\fR function, so it will include the \s-1VMS\s0 message for
VMS-specific errors. The numeric value of \f(CW$!\fR is the
value of \f(CW\*(C`errno\*(C'\fR, except if errno is \s-1EVMSERR\s0, in which
case \f(CW$!\fR contains the value of vaxc$errno. Setting \f(CW$!\fR
always sets errno to the value specified. If this value is
\&\s-1EVMSERR\s0, it also sets vaxc$errno to 4 (\s-1NONAME\-F\-NOMSG\s0), so
that the string value of \f(CW$!\fR won't reflect the \s-1VMS\s0 error
message from before \f(CW$!\fR was set.
.IP "$^E" 4
.IX Item "$^E"
This variable provides direct access to \s-1VMS\s0 status values
in vaxc$errno, which are often more specific than the
generic Unix-style error messages in \f(CW$!\fR. Its numeric value
is the value of vaxc$errno, and its string value is the
corresponding \s-1VMS\s0 message string, as retrieved by sys$\fIgetmsg()\fR.
Setting \f(CW$^E\fR sets vaxc$errno to the value specified.
.IP "$?" 4
The \*(L"status value\*(R" returned in \f(CW$?\fR is synthesized from the
actual exit status of the subprocess in a way that approximates
\&\s-1POSIX\s0 \fIwait\fR\|(5) semantics, in order to allow Perl programs to
portably test for successful completion of subprocesses. The
low order 8 bits of \f(CW$?\fR are always 0 under \s-1VMS\s0, since the
termination status of a process may or may not have been
generated by an exception. The next 8 bits are derived from
the severity portion of the subprocess' exit status: 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 fatal error.
.Sp
As a result, \f(CW$?\fR will always be zero if the subprocess' exit
status indicated successful completion, and non-zero if a
warning or error occurred. Conversely, when setting \f(CW$?\fR in
an \s-1END\s0 block, an attempt is made to convert the \s-1POSIX\s0 value
into a native status intelligible to the operating system upon
exiting Perl. What this boils down to is that setting \f(CW$?\fR
to zero results in the generic success value \s-1SS$_NORMAL\s0, and
setting \f(CW$?\fR to a non-zero value results in the generic
failure status \s-1SS$_ABORT\s0. See also \*(L"exit\*(R" in perlport.
.Sp
The pragma \f(CW\*(C`use vmsish 'status'\*(C'\fR makes \f(CW$?\fR reflect the actual
\&\s-1VMS\s0 exit status instead of the default emulation of \s-1POSIX\s0 status
described above. This pragma also disables the conversion of
non-zero values to \s-1SS$_ABORT\s0 when setting \f(CW$?\fR in an \s-1END\s0
block (but zero will still be converted to \s-1SS$_NORMAL\s0).
.IP "$|" 4
Setting \f(CW$|\fR for an I/O stream causes data to be flushed
all the way to disk on each write (\fIi.e.\fR not just to
the underlying \s-1RMS\s0 buffers for a file). In other words,
it's equivalent to calling \fIfflush()\fR and \fIfsync()\fR from C.
.SH "Standard modules with VMS-specific differences"
.IX Header "Standard modules with VMS-specific differences"
.Sh "SDBM_File"
.IX Subsection "SDBM_File"
SDBM_File works properly on \s-1VMS\s0. It has, however, one minor
difference. The database directory file created has a \fI.sdbm_dir\fR
extension rather than a \fI.dir\fR extension. \fI.dir\fR files are \s-1VMS\s0 filesystem
directory files, and using them for other purposes could cause unacceptable
problems.
.SH "Revision date"
.IX Header "Revision date"
This document was last updated on 01\-May\-2002, for Perl 5,
patchlevel 8.
.SH "AUTHOR"
.IX Header "AUTHOR"
Charles Bailey bailey@cor.newman.upenn.edu
Craig Berry craigberry@mac.com
Dan Sugalski dan@sidhe.org
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