=head1 NAME perlvms - VMS-specific documentation for Perl =head1 DESCRIPTION Gathered below are notes describing details of Perl 5's behavior on VMS. They are a supplement to the regular Perl 5 documentation, so we have focussed on the ways in which Perl 5 functions differently under VMS than it does under Unix, and on the interactions between Perl and the rest of the operating system. We haven't tried to duplicate complete descriptions of 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 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 Organization of Perl Images =head2 Core 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. =head2 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). =head2 Installing dynamic extensions In general, the distributed kit for a Perl extension includes a file named Makefile.PL, which is a Perl program which is used to create a F file which can be used to build and install the files required by the extension. The kit should be unpacked into a directory tree B under the main Perl source directory, and the procedure for building the extension is simply $ perl Makefile.PL ! Create Descrip.MMS $ mmk ! Build necessary files $ mmk test ! Run test code, if supplied $ mmk install ! Install into public Perl tree I The procedure by which extensions are built and tested creates several levels (at least 4) under the directory in which the extension's source files live. For this reason, you shouldn't nest the source directory too deeply in your directory structure, lest you eccedd RMS' maximum of 8 levels of subdirectory in a filespec. (You can use rooted logical names to get another 8 levels of nesting, if you can't place the files near the top of the physical directory structure.) VMS support for this process in the current release of Perl is sufficient to handle most extensions. However, it does not yet recognize extra libraries required to build shareable images which are part of an extension, so these must be added to the linker options file for the extension by hand. For instance, if the F extension to Perl requires the F shareable image in order to properly link the Perl extension, then the line C must be added to the linker options file F produced during the build process for the Perl extension. By default, the shareable image for an extension is placed in the F<[.Lib.Auto.>I.IF<]> directory of the installed Perl directory tree (where I is F or F, followed by the Perl version number, and I is the name of the extension, with each C<::> translated to C<.>). However, it can be manually placed in any of several locations: - the F<[.Lib.Auto.>IF<]> subdirectory of one of the directories in C<@INC>, 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. =head1 File specifications =head2 Syntax We have tried to make Perl aware of both VMS-style and Unix- style file specifications wherever possible. You may use either style, or both, on the command line and in scripts, but you may not combine the two styles within a single fle specification. Filenames are, of course, still case- insensitive. For consistency, most Perl routines return filespecs using lower case letters only, regardless of the case used in the arguments passed to them. (This is true only when running under VMS; Perl respects the case- sensitivity of OSs like Unix.) We've tried to minimize the dependence of Perl library modules on Unix syntax, but you may find that some of these, as well as some scripts written for Unix systems, will require that you use Unix syntax, since they will assume that '/' is the directory separator, I If you find instances of this in the Perl distribution itself, please let us know, so we can try to work around them. =head2 Wildcard expansion File specifications containing wildcards are allowed both on the command line and within Perl globs (e.g. *.cE>). 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 contain the file version only if one was present in the input filespec. =head2 Pipes Input and output pipes to Perl filehandles are supported; the "file name" is passed to lib$spawn() for asynchronous execution. You should be careful to close any pipes you have opened in a Perl script, lest you leave any "orphaned" subprocesses around when Perl exits. You may also use backticks to invoke a DCL subprocess, whose output is used as the return value of the expression. The string between the backticks is passed directly to lib$spawn as the command to execute. In this case, Perl will wait for the subprocess to complete before continuing. =head1 PERL5LIB and PERLLIB The PERL5LIB and PERLLIB logical names work as documented L, except that the element separator is '|' instead of ':'. The directory specifications may use either VMS or Unix syntax. =head1 Command line =head2 I/O redirection and backgrounding Perl for VMS supports redirection of input and output on the command line, using a subset of Bourne shell syntax: 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. =head2 Command line switches The following command line switches behave differently under VMS than described in L. 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. =item -S If the C<-S> switch is present I the script name does not contain a directory, then Perl translates the logical name DCL$PATH as a searchlist, using each translation as a directory in which to look for the script. In addition, if no file type is specified, Perl looks in each directory for a file matching the name specified, with a blank type, a type of F<.pl>, and a type of F<.com>, in that order. =item -u The C<-u> switch causes the VMS debugger to be invoked after the Perl program is compiled, but before it has run. It does not create a core dump file. =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, crypt*, defined, delete, die, do, dump*, each, endpwent, eof, eval, exec*, exists, exit, exp, fileno, fork*, getc, getlogin, getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto, grep, hex, import, index, int, join, keys, kill*, last, lc, lcfirst, length, local, localtime, log, m//, map, mkdir, my, next, no, oct, open, opendir, ord, pack, pipe, pop, pos, print, printf, push, q//, qq//, qw//, qx//, quotemeta, rand, read, readdir, redo, ref, rename, require, reset, return, reverse, rewinddir, rindex, rmdir, s///, scalar, seek, seekdir, select(internal), select (system call)*, setpwent, shift, sin, sleep, sort, splice, split, sprintf, sqrt, srand, stat, study, substr, sysread, system*, syswrite, tell, telldir, tie, time, times*, tr///, uc, ucfirst, umask, undef, unlink*, unpack, untie, unshift, use, utime*, values, vec, wait, waitpid*, wantarray, warn, write, y/// The following functions were not implemented in the VMS port, and calling them produces a fatal error (usually) or undefined behavior (rarely, we hope): chroot, dbmclose, dbmopen, fcntl, flock, getpgrp, getppid, getpriority, getgrent, getgrgid, getgrnam, setgrent, endgrent, ioctl, link, lstat, msgctl, msgget, msgsend, msgrcv, readlink, semctl, semget, semop, setpgrp, setpriority, shmctl, shmget, shmread, shmwrite, socketpair, symlink, syscall, 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, select(system call)*, 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. Note: Some sites have reported problems when using the file-access tests (C<-r>, C<-w>, and C<-x>) on files accessed via DEC's DFS. Specifically, since DFS does not currently provide access to the extended file header of files on remote volumes, attempts to examine the ACL fail, and the file tests will return false, with C<$!> indicating that the file does not exist. You can use C on these files, since that checks UIC-based protection only, and then manually check the appropriate bits, as defined by your C compiler's F, in the mode value it returns, if you need an approximation of the file's protections. =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 crypt PLAINTEXT, USER The C operator uses the C system service to generate the hashed representation of PLAINTEXT. If USER is a valid username, the algorithm and salt values are taken from that user's UAF record. If it is not, then the preferred algorithm and a salt of 0 are used. The quadword encrypted value is returned as an 8-character string. The value returned by C may be compared against the encrypted password from the UAF returned by the C functions, in order to authenticate users. If you're going to do this, remember that the encrypted password in the UAF was generated using uppercase username and password strings; you'll have to upcase the arguments to C to insure that you'll get the proper value: sub validate_passwd { my($user,$passwd) = @_; my($pwdhash); if ( !($pwdhash = (getpwnam($user))[1]) || $pwdhash ne crypt("\U$passwd","\U$name") ) { intruder_alert($name); } return 1; } =item dump Rather than causing Perl to abort and dump core, the C operator invokes the VMS debugger. If you continue to execute the Perl program under the debugger, control will be transferred to the label specified as the argument to C, or, if no label was specified, back to the beginning of the program. All other state of the program (I values of variables, open file handles) are not affected by calling C. =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 gmtime The C operator will function properly if you have a working CRTL C routine, or if the logical name SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds which must be added to UTC to yield local time. (This logical name is defined automatically if you are running a version of VMS with built-in UTC support.) If neither of these cases is true, a warning message is printed, and C is returned. =item kill In most cases, C kill is implemented via the CRTL's C function, so it will behave according to that function's documentation. If you send a SIGKILL, however, the $DELPRC system service is is called directly. This insures that the target process is actually deleted, if at all possible. (The CRTL's C function is presently implemented via $FORCEX, which is ignored by supervisor-mode images like DCL.) Also, negative signal values don't do anything special under VMS; they're just converted to the corresponding positive value. =item select (system call) If Perl was not built with socket support, the system call version of C functions only for file descriptors attached to sockets. It will not provide information about regular files or pipes, since the CRTL C routine does not provide this functionality. =item stat EXPR Since VMS keeps track of files according to a different scheme than Unix, it's not really possible to represent the file's ID in the C 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 C, 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; } (or you could just use C, if you've installed the VMS::Stdio extension distributed with Perl). 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 Perl variables =item %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. If you append a semicolon to the logical name, followed by an integer, that integer is used as the translation index for the logical name, so that you can 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 $ENV{'foo'.$i},' '}" Perl will print C. The %ENV keys C, C,C, and C return the CRTL "environment variables" of the same names, if these logical names are not defined. The key C returns the current default device and directory specification, regardless of whether there is a logical name DEFAULT defined.. 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. It is not possible at present to define a search list logical name via %ENV. In all operations on %ENV, the key string is treated as if it were entirely uppercase, regardless of the case actually specified in the Perl expression. =item $? Since VMS status values are 32 bits wide, the value of C<$?> is simply the final status value of the last subprocess to complete. This differs from the behavior of C<$?> under Unix, and under VMS' POSIX environment, in that the low-order 8 bits of C<$?> do not specify whether the process terminated normally or due to a signal, and you do not need to shift C<$?> 8 bits to the right in order to find the process' exit status. =item $! The string value of C<$!> is that returned by the CRTL's strerror() function, so it will include the VMS message for VMS-specific errors. The numeric value of C<$!> is the value of C, except if errno is EVMSERR, in which case C<$!> contains the value of vaxc$errno. Setting C<$!> always sets errno to the value specified. If this value is EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-NOMSG), so that the string value of C<$!> won't reflect the VMS error message from before C<$!> was set. =item $^E This variable provides direct access to VMS status values in vaxc$errno, which are often more specific than the generic Unix-style error messages in C<$!>. Its numeric value is the value of vaxc$errno, and its string value is the corresponding VMS message string, as retrieved by sys$getmsg(). Setting C<$^E> sets vaxc$errno to the value specified. =item $| Setting C<$|> for an I/O stream causes data to be flushed all the way to disk on each write (I not just to the underlying RMS buffers for a file). In other words, it's equivalent to calling fflush() and fsync() from C. =head1 Revision date This document was last updated on 28-Feb-1996, for Perl 5, patchlevel 2. =head1 AUTHOR Charles Bailey bailey@genetics.upenn.edu