=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@perl.org. =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 if you are runnning 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 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.site_perl.auto>I.IF<]> directory of the installed Perl directory tree (where I is F or F, and I is the name of the extension, with each C<::> translated to C<.>). (See the MakeMaker documentation for more details on installation options for extensions.) However, it can be manually placed in any of several locations: =over 4 =item * the F<[.Lib.Auto.>II<$PVers>IF<]> subdirectory of one of the directories in C<@INC> (where I is the version of Perl you're using, as supplied in C<$]>, with '.' converted to '_'), or =item * one of the directories in C<@INC>, or =item * a directory which the extensions Perl library module passes to the DynaLoader when asking it to map the shareable image, or =item * F or F. =back 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 file specification. VMS Perl interprets Unix pathnames in much the same way as the CRTL (I the first component of an absolute path is read as the device name for the VMS file specification). There are a set of functions provided in the C package for explicit interconversion between VMS and Unix syntax; its documentation provides more details. Filenames are, of course, still case-insensitive. For consistency, most Perl routines return filespecs using lower case letters only, regardless of the case used in the arguments passed to them. (This is true only when running under VMS; Perl respects the case-sensitivity of OSs like Unix.) We've tried to minimize the dependence of Perl library modules on Unix syntax, but you may find that some of these, as well as some scripts written for Unix systems, will require that you use Unix syntax, since they will assume that '/' is the directory separator, 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. C*.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. Similar to the behavior of wildcard globbing for a Unix shell, one can escape command line wildcards with double quotation marks C<"> around a perl program command line argument. However, owing to the stripping of C<"> 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 F, F, F, and F): $ 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.* In both the case of unquoted command line arguments or in calls to C VMS wildcard expansion is performed. (csh-style wildcard expansion is available if you use C.) 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$spawn() for asynchronous execution. You should be careful to close any pipes you have opened in a Perl script, lest you leave any "orphaned" subprocesses around when Perl exits. You may also use backticks to invoke a DCL subprocess, whose output is used as the return value of the expression. The string between the backticks is handled as if it were the argument to the C operator (see below). In this case, Perl will wait for the subprocess to complete before continuing. The mailbox (MBX) that perl can create to communicate with a pipe defaults to a buffer size of 512. The default buffer size is adjustable via the logical name PERL_MBX_SIZE provided that the value falls between 128 and the SYSGEN parameter MAXBUF inclusive. For example, to double the MBX size from the default within a Perl program, use C<$ENV{'PERL_MBX_SIZE'} = 1024;> and then open and use pipe constructs. An alternative would be to issue the command: $ Define PERL_MBX_SIZE 1024 before running your wide record pipe program. A larger value may improve performance at the expense of the BYTLM UAF quota. =head1 PERL5LIB and PERLLIB The PERL5LIB and PERLLIB logical names work as documented in 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: =over 4 =item * Cfile> reads stdin from C, =item * Cfile> writes stdout to C, =item * CEfile> appends stdout to C, =item * C<2Efile> writes stderr to C, =item * C<2EEfile> appends stderr to C, and =item * C<< 2>&1 >> redirects stderr to stdout. =back 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. =over 4 =item -i If the C<-i> switch is present but no extension for a backup copy is given, then inplace editing creates a new version of a file; the existing copy is not deleted. (Note that if an extension is given, an existing file is renamed to the backup file, as is the case under other operating systems, so it does not remain as a previous version under the original filename.) =item -S If the C<"-S"> or 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. =back =head1 Perl functions As of the time this document was last revised, the following Perl functions were implemented in the VMS port of Perl (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, 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/// 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, 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 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 =over 4 =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 backticks Backticks create a subprocess, and pass the enclosed string to it for execution as a DCL command. Since the subprocess is created directly via C, any valid DCL command string may be specified. =item binmode FILEHANDLE The C operator will attempt to insure that no translation of carriage control occurs on input from or output to this filehandle. Since this involves reopening the file and then restoring its file position indicator, if this function returns FALSE, the underlying filehandle may no longer point to an open file, or may point to a different position in the file than before C was called. Note that C is generally not necessary when using normal filehandles; it is provided so that you can control I/O to existing record-structured files when necessary. You can also use the C function in the VMS::Stdio extension to gain finer control of I/O to files and devices with different record structures. =item crypt PLAINTEXT, USER The C 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 A call to C will cause Perl to exit, and to invoke the command given as an argument to C via C. If the argument begins with '@' or '$' (other than as part of a filespec), then it is executed as a DCL command. Otherwise, the first token on the command line is treated as the filespec of an image to run, and an attempt is made to invoke it (using F<.Exe> and the process defaults to expand the filespec) and pass the rest of C's argument to it as parameters. If the token has no file type, and matches a file with null type, then an attempt is made to determine whether the file is an executable image which should be invoked using C or a text file which should be passed to DCL as a command procedure. =item fork While in principle the C operator could be implemented via (and with the same rather severe limitations as) the CRTL C routine, and while some internal support to do just that is in place, the implementation has never been completed, making C currently unavailable. A true kernel C is expected in a future version of VMS, and the pseudo-fork based on interpreter threads may be available in a future version of Perl on VMS (see L). In the meantime, use C, backticks, or piped filehandles to create subprocesses. =item getpwent =item getpwnam =item getpwuid These operators obtain the information described in L, if you have the privileges necessary to retrieve the named user's UAF information via C. If not, then only the C<$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 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 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 qx// See the entry on C above. =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 the string begins with '@', it is treated as a DCL command unconditionally. Otherwise, if the first token contains a character used as a delimiter in file specification (e.g. C<:> or C<]>), an attempt is made to expand it using a default type of F<.Exe> and the process defaults, and if successful, the resulting file is invoked via C. This allows you to invoke an image directly simply by passing the file specification to C, a common Unixish idiom. If the token has no file type, and matches a file with null type, then an attempt is made to determine whether the file is an executable image which should be invoked using C or a text file which should be passed to DCL as a command procedure. If LIST consists of the empty string, C spawns an interactive DCL subprocess, in the same fashion as typing B at the DCL prompt. Perl waits for the subprocess to complete before continuing execution in the current process. As described in L, the return value of C is a fake "status" which follows POSIX semantics unless the pragma C is in effect; see the description of C<$?> in this document for more detail. =item time The value returned by C