=head1 Notes on Perl 5 for VMS 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 F<[.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@genetics.upenn.edu. =head1 Organization of Perl =head2 Perl Images During the installation process, three Perl images are produced. F is an executable image which contains all of the basic functionality of Perl, but cannot take advantage of Perl extensions. It is used to generate several files needed to build the complete Perl and various extensions. Once you've finished installing Perl, you can delete this image. Most of the complete Perl resides in the shareable image F, which provides a core to which the Perl executable image and all Perl extensions are linked. You should place this image in F, or define the logical name F to translate to the full file specification of this image. It should be world readable. (Remember that if a user has execute only access to F, VMS will treat it as if it were a privileged shareable image, and will therefore require all downstream shareable images to be INSTALLed, etc.) Finally, F is an executable image containing the main entry point for Perl, as well as some initialization code. It should be placed in a public directory, and made world executable. In order to run Perl with command line arguments, you should define a foreign command to invoke this image. =head2 Perl Extensions Perl extensions are packages which provide both XS and Perl code to add new functionality to perl. (XS is a meta-language which simplifies writing C code which interacts with Perl, see L for more details.) The Perl code for an extension is treated like any other library module - it's made available in your script through the appropriate C or C statement, and usually defines a Perl package containing the extension. The portion of the extension provided by the XS code may be connected to the rest of Perl in either of two ways. In the B configuration, the object code for the extension is linked directly into F, and is initialized whenever Perl is invoked. In the B configuration, the extension's machine code is placed into a separate shareable image, which is mapped by Perl's DynaLoader when the extension is Cd or Cd 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: IF<.xs> (where I is the portion of the extension's name following the last C<::>), containing the XS code, IF<.pm>, the Perl library module for the extension, and F, a Perl script which uses the C library modules supplied with Perl to generate a F file for the extension. =head3 Installing static extensions Since static extensions are incorporated directly into F, you'll have to rebuild Perl to incorporate a new extension. You should edit the main F or F you use to build Perl, adding the extension's name to the C macro, and the extension's object file to the C macro. You'll also need to build the extension's object file, either by adding dependencies to the main F, or using a separate F for the extension. Then, rebuild F to incorporate the new code. Finally, you'll need to copy the extension's Perl library module to the F<[.>IF<]> subdirectory under one of the directories in C<@INC>, where I is the name of the extension, with all C<::> replaced by C<.> (e.g. the library module for extension Foo::Bar would be copied to a F<[.Foo.Bar]> subdirectory). =head3 Installic dynamic extensions First, you'll need to compile the XS code into a shareable image, either by hand or using the F supplied with the extension. If you're building the shareable image by hand, please note the following points: - The shareable image must be linked to F, so it has access to Perl's global variables and routines. In order to specify the correct attributes for psects in F, you should include the linker options file F in the Link command. (This file is generated when F is built, and is found in the main Perl source directory. - The entry point for the CI routine (where I is the name of the extension, with all C<::> replaced by C<__>) must be a universal symbol. No other universal symbols are required to use the shareable image with Perl, though you may want to include additional universal symbols if you plan to share code or data among different extensions. The shareable image can be placed in any of several locations: - the F<[.Auto.>IF<]> subdirectory of one of the directories in C<@INC>, where I is the name of the extension, with each C<::> translated to C<.> (e.g. for extension Foo::Bar, you would use the F<[.Auto.Foo.Bar]> subdirectory), or - one of the directories in C<@INC>, or - a directory which the extensions Perl library module passes to the DynaLoader when asking it to map the shareable image, or - F or F. If the shareable image isn't in any of these places, you'll need to define a logical name I, where I is the portion of the extension's name after the last C<::>, which translates to the full file specification of the shareable image. Once you've got the shareable image set up, you should copy the extension's Perl library module to the appropriate library directory (see the section above on installing static extensions). =head1 Installation Directions for building and installing Perl 5 can be found in the file F in the main source directory of the Perl distribution.. =head1 File specifications We have tried to make Perl aware of both VMS-style and Unix- style file specifications wherever possible. You may use either style, or both, on the command line and in scripts, but you may not combine the two styles within a single fle specfication. Filenames are, of course, still case- insensitive. For consistency, most Perl routines return filespecs using lower case latters only, regardless of the case used in the arguments passed to them. (This is true only when running under VMS; Perl respects the case- sensitivity of OSs like Unix.) We've tried to minimize the dependence of Perl library modules on Unix syntax, but you may find that some of these, as well as some scripts written for Unix systems, will require that you use Unix syntax, since they will assume that '/' is the directory separator, etc. If you find instances of this in the Perl distribution itself, please let us know, so we can try to work around them. =head1 Command line redirection Perl for VMS supports redirection of input and output on the command line, using a subset of Bourne shell syntax: reads stdin from F, >F writes stdout to F, >>F appends stdout to F, 2>F writes stderr to F, and 2>>F appends stderr to F. 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. =head1 Pipes Input and output pipes to Perl filehandles are supported; the "file name" is passed to lib$spawn() for asynchronous execution. You should be careful to close any pipes you have opened in a Perl script, lest you leave any "orphaned" subprocesses around when Perl exits. You may also use backticks to invoke a DCL subprocess, whose output is used as the return value of the expression. The string between the backticks is passed directly to lib$spawn as the command to execute. In this case, Perl will wait for the subprocess to complete before continuing. =head1 Wildcard expansion File specifications containing wildcards are allowed both on the command line and within Perl globs (e.g. >). If the wildcard filespec uses VMS syntax, the resultant filespecs will follow VMS syntax; if a Unix-style filespec is passed in, Unix-style filespecs will be returned.. If the wildcard filespec contains a device or directory specification, then the resultant filespecs will also contain a device and directory; otherwise, device and directory information are removed. VMS-style resultant filespecs will contain a full device and directory, while Unix-style resultant filespecs will contain only as much of a directory path as was present in the input filespec. For example, if your default directory is Perl_Root:[000000], the expansion of C<[.t]*.*> will yield filespecs like "perl_root:[t]base.dir", while the expansion of C 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 the file version only if one was present in the input filespec. =head1 PERL5LIB and PERLLIB The PERL5LIB and PERLLIB logical names work as documented L, except that the element separator is '|' instead of ':'. The directory specifications may use either VMS or Unix syntax. =head1 %ENV Reading the elements of the %ENV array returns the translation of the logical name specified by the key, according to the normal search order of access modes and logical name tables. In addition, the keys C, C,C, and C return the CRTL "environment variables" of the same names. The key C returns the current default device and directory specification. Setting an element of %ENV defines a supervisor-mode logical name in the process logical name table. Cing or Cing an element of %ENV deletes the equivalent user- mode or supervisor-mode logical name from the process logical name table. If you use C, the %ENV element remains empty. If you use C, another attempt is made at logical name translation after the deletion, so an inner-mode logical name or a name in another logical name table will replace the logical name just deleted. 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. =head1 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, binmode*, bless, caller, chdir, chmod, chown, chomp, chop, chr, close, closedir, cos, defined, delete, die, do, each, endpwent, eof, eval, exec*, exists, exit, exp, fileno, fork*, getc, getpwent*, getpwnam*, getpwuid*, glob, goto, grep, hex, import, index, int, join, keys, kill, last, lc, lcfirst, length, local, localtime, log, m//, map, mkdir, my, next, no, oct, open, opendir, ord, pack, pipe, pop, pos, print, printf, push, q//, qq//, qw//, qx//, quotemeta, rand, read, readdir, redo, ref, rename, require, reset, return, reverse, rewinddir, rindex, rmdir, s///, scalar, seek, seekdir, select(internal)*, setpwent, shift, sin, sleep, sort, splice, split, sprintf, sqrt, srand, stat, study, substr, sysread, system*, syswrite, tell, telldir, tie, time, times*, tr///, uc, ucfirst, umask, undef, unlink*, unpack, untie, unshift, use, utime*, values, vec, wait, waitpid*, wantarray, warn, write, y/// The following functions were not implemented in the VMS port, and calling them produces a fatal error (usually) or undefined behavior (rarely, we hope): chroot, crypt, dbmclose, dbmopen, dump, fcntl, flock, getlogin, getpgrp, getppid, getpriority, getgrent, kill, getgrgid, getgrnam, setgrent, endgrent, gmtime, ioctl, link, lstst, msgctl, msgget, msgsend, msgrcv, readlink, select(system call), semctl, semget, semop, setpgrp, setpriority, shmctl, shmget, shmread, shmwrite, socketpair, symlink, syscall, truncate 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, send, setsockopt, shutdown, socket =item File tests The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>, C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as advertised. The return values for C<-r>, C<-w>, and C<-x> tell you whether you can actually access the file; this may not reflect the UIC-based file protections. Since real and effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>, and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>. Similarly, several other tests, including C<-A>, C<-g>, C<-k>, C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under VMS, and the values returned by these tests reflect whatever your CRTL C routine does to the equivalent bits in the st_mode field. Finally, C<-d> returns true if passed a device specification without an explicit directory (e.g. C), as well as if passed a directory. =item binmode FILEHANDLE The C operator has no effect under VMS. It will return TRUE whenever called, but will not affect I/O operations on the filehandle given as its argument. =item exec LIST The C operator behaves in one of two different ways. If called after a call to C, it will invoke the CRTL C routine, passing its arguments to the subprocess created by C for execution. In this case, it is subject to all limitations that affect C. (In particular, this usually means that the command executed in the subprocess must be an image compiled from C source code, and that your options for passing file descriptors and signal handlers to the subprocess are limited.) If the call to C does not follow a call to C, it will cause Perl to exit, and to invoke the command given as an argument to C via C. If the argument begins with a '$' (other than as part of a filespec), then it is executed as a DCL command. Otherwise, the first token on the command line is treated as the filespec of an image to run, and an attempt is made to invoke it (using F<.Exe> and the process defaults to expand the filespec) and pass the rest of C's argument to it as parameters. You can use C in both ways within the same script, as long as you call C and C in pairs. Perl keeps track of how many times C and C have been called, and will call the CRTL C routine if there have previously been more calls to C than to C. =item fork The C operator works in the same way as the CRTL C routine, which is quite different under VMS than under Unix. Specifically, while C returns 0 after it is called and the subprocess PID after C is called, in both cases the thread of execution is within the parent process, so there is no opportunity to perform operations in the subprocess before calling C. In general, the use of C and C to create subprocess is not recommended under VMS; wherever possible, use the C operator or piped filehandles instead. =item getpwent =item getpwnam =item getpwuid These operators obtain the information described in L, if you have the privileges necessary to retrieve the named user's UAF information via C. If not, then only the C<$name>, C<$uid>, and C<$gid> items are returned. The C<$dir> item contains the login directory in VMS syntax, while the C<$comment> item contains the login directory in Unix syntax. The C<$gcos> item contains the owner field from the UAF record. The C<$quota> item is not used. =item stat EXPR Since VMS keeps track of files according to a different scheme than Unix, it's not really possible to represent the file's ID in the C and C fields of a C. Perl tries its best, though, and the values it uses are pretty unlikely to be the same for two different files. We can't guarantee this, though, so caveat scriptor. =item system LIST The C 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$spawn, any valid DCL command string may be specified. If LIST consists of the empty string, C spawns an interactive DCL subprocess, in the same fashion as typiing B at the DCL prompt. Perl waits for the subprocess to complete before continuing execution in the current process. =item times The array returned by the C operator is divided up according to the same rules the CRTL C routine. Therefore, the "system time" elements will always be 0, since there is no difference between "user time" and "system" time under VMS, and the time accumulated by subprocess may or may not appear separately in the "child time" field, depending on whether L keeps track of subprocesses separately. Note especially that the VAXCRTL (at least) keeps track only of subprocesses spawned using L and L; it will not accumulate the times of suprocesses spawned via pipes, L, or backticks. =item unlink LIST C will delete the highest version of a file only; in order to delete all versions, you need to say 1 while (unlink LIST); You may need to make this change to scripts written for a Unix system which expect that after a call to C, no files with the names passed to C will exist. (Note: This can be changed at compile time; if you C and C<$Config{'d_unlink_all_versions'}> is C, then C will delete all versions of a file on the first call.) C will delete a file if at all possible, even if it requires changing file protection (though it won't try to change the protection of the parent directory). You can tell whether you've got explicit delete access to a file by using the C 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; } Finally, if C has to change the file protection to delete the file, and you interrupt it in midstream, the file may be left intact, but with a changed ACL allowing you delete access. =item utime LIST Since ODS-2, the VMS file structure for disk files, does not keep track of access times, this operator changes only the modification time of the file (VMS revision date). =item waitpid PID,FLAGS If PID is a subprocess started by a piped L, C will wait for that subprocess, and return its final status value. If PID is a subprocess created in some other way (e.g. SPAWNed before Perl was invoked), or is not a subprocess of the current process, C will check once per second whether the process has completed, and when it has, will return 0. (If PID specifies a process that isn't a subprocess of the current process, and you invoked Perl with the C<-w> switch, a warning will be issued.) The FLAGS argument is ignored in all cases. =head1 Revision date This document was last updated on 16-Dec-1994, for Perl 5, patchlevel 0.