=head1 Notes on Perl5 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 thatn it does under Unix, and on teh interactions between perl and the rest of the operating system. We haven't tried to duplicate complete descriptions of perl5 features from the main perl documentation, which can be found in the F<[.pod]> subdirectory of the perl 5 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. =head2 Installation Directions for building and installing perl 5 can be found in the file F in the main source directory of the perl5 distribution.. =head2 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 perl5 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; perl5 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. =head2 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 wrtits 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 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. =head2 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. =head2 %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. Bing or Bing an element of %ENV deletes the equivalent user- mode or supervisor-mode logical name from the process logical name table. If you use B, the %ENV element remains empty. If you use B, 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. =head2 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, eof, eval, exec*, exists, exit, exp, fileno, fork*, getc, 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)*, 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, values, vec, wait, 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, getpwent, getgrent, kill, getgrgid, getgrnam, getpwnam, getpwuid, setpwent, setgrent, endpwent, 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, utime, waitpid 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 -b, -B, -c, -C, -d, -e, -f, -o, -M, -s, -S, -t, -T, and -z work as advertised. The return values for -r, -w, and -x tell you whether you can actually access the file; this may mot reflect the UIC-based file protections. Since real and effective UIC don't differ under VMS, -O, -R, -W, and -X are equivalent to -o, -r, -w, and -x. Similarly, several other tests, including -A, -g, -k, -l,-p, and -u, aren't particularly meaningful under VMS, and the values returned by these tests reflect whatever your CRTL stat() routine does to the equivalent bits in the st_mode field. =item binmode The B 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 The B operator behaves in one of two different ways. If called after a call to B, it will invoke the CRTL L routine, passing its arguments to the subprocess created by B for execution. In this case, it is subject to all limitation that affect L. (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 B does not follow a call to B, it will cause perl to exit, and to invoke the command given as an argument to B via lib$do_command. If the argument begins with a '$' (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 B's argument to it as parameters. You can use B in both ways within the same script, as long as you call B and B in pairs. Perl only keeps track of whether B has been called since the last call to B when figuring out what to do, so multiple calls to B do not generate multiple levels of "fork context". =item fork The B operator works in the same way as the CRTL L routine, which is quite different under VMS than under Unix. Sepcifically, while B returns 0 after it is called and the subprocess PID after B 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 B. In general, the use of B and B to create subprocess is not recommended under VMS; wherever possible, use the B operator or piped filehandles instead. =item system The B 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. Perl waits for the subprocess to complete before continuing execution in the current process. =item times The array returned by the B operator is divided up according to the same rules the CRTL L 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. =head2 Revision date This document was last updated on 16-Oct-1994, for perl 5, patchlevel 0.