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@newman.upenn.edu.
+hesitate to drop a line to vmsperl@perl.org.
=head1 Installation
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'
+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
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
+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<e.g.> the first component of
an absolute path is read as the device name for the
=head2 Wildcard expansion
File specifications containing wildcards are allowed both on
-the command line and within Perl globs (e.g. <CE<lt>*.cE<gt>>). If
+the command line and within Perl globs (e.g. C<E<lt>*.cE<gt>>). 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.
=head1 PERL5LIB and PERLLIB
-The PERL5LIB and PERLLIB logical names work as documented L<perl>,
+The PERL5LIB and PERLLIB logical names work as documented
in L<perl>,
except that the element separator is '|' instead of ':'. The
directory specifications may use either VMS or Unix syntax.
Perl for VMS supports redirection of input and output on the
command line, using a subset of Bourne shell syntax:
- <F<file> reads stdin from F<file>,
- >F<file> writes stdout to F<file>,
- >>F<file> appends stdout to F<file>,
- 2>F<file> writes stderr to F<file>, and
- 2>>F<file> appends stderr to F<file>.
+=over
+
+=item *
+
+C<E<lt>file> reads stdin from C<file>,
+
+=item *
+
+C<E<gt>file> writes stdout to C<file>,
+
+=item *
+
+C<E<gt>E<gt>file> appends stdout to C<file>,
+
+=item *
+
+C<2E<gt>file> writes stderr to C<file>, and
+
+=item *
+
+C<2E<gt>E<gt>file> appends stderr to C<file>.
+
+=back
In addition, output may be piped to a subprocess, using the
character '|'. Anything after this character on the command
and calling them produces a fatal error (usually) or
undefined behavior (rarely, we hope):
- chroot, dbmclose, dbmopen, fcntl, flock,
+ chroot, dbmclose, dbmopen, 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
-The following functions are available on Perls compiled with Dec C 5.2 or
-greater and running VMS 7.0 or greater
+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:
the subprocess before calling C<exec>.
In general, the use of C<fork> and C<exec> to create
-subprocess is not recommended under VMS; wherever possible,
+subprocesses is not recommended under VMS; wherever possible,
use the C<system> operator or piped filehandles instead.
=item getpwent
=item kill
-In most cases, C<kill> kill is implemented via the CRTL's C<kill()>
+In most cases, C<kill> is implemented via the CRTL's C<kill()>
function, so it will behave according to that function's
documentation. If you send a SIGKILL, however, the $DELPRC system
service is called directly. This insures that the target
Perl waits for the subprocess to complete before continuing
execution in the current process. As described in L<perlfunc>,
the return value of C<system> is a fake "status" which follows
-POSIX semantics; see the description of C<$?> in this document
-for more detail. The actual VMS exit status of the subprocess
-is available in C<$^S> (as long as you haven't used another Perl
-function that resets C<$?> and C<$^S> in the meantime).
+POSIX semantics unless the pragma C<use vmsish 'status'> is in
+effect; see the description of C<$?> in this document for more
+detail.
=item time
according to the same rules the CRTL C<times()> 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
+under VMS, and the time accumulated by a subprocess may or may
not appear separately in the "child time" field, depending on
whether L<times> keeps track of subprocesses separately. Note
especially that the VAXCRTL (at least) keeps track only of
C<unlink> will delete the highest version of a file only; in
order to delete all versions, you need to say
- 1 while (unlink LIST);
+
+ 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<unlink>,
no files with the names passed to C<unlink> will exist.
=item waitpid PID,FLAGS
-If PID is a subprocess started by a piped L<open>, C<waitpid>
-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<waitpid> 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.
+If PID is a subprocess started by a piped C<open()> (see L<open>),
+C<waitpid> will wait for that subprocess, and return its final
+status value in C<$?>. If PID is a subprocess created in some other
+way (e.g. SPAWNed before Perl was invoked), or is not a subprocess
+of the current process, C<waitpid> will attempt to read from the
+process's termination mailbox, making the final status available in
+C<$?> when the process completes. If the process specified by PID
+has no termination mailbox, C<waitpid> will simply check once per
+second whether the process has completed, and return when it has.
+(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.)
+
+Returns PID on success, -1 on error. The FLAGS argument is ignored
+in all cases.
=back
by the global symbol table.. The characters following C<CLISYM_> are
significant when an element of C<%ENV> is set or deleted: if the
complete string is C<CLISYM_LOCAL>, the change is made in the local
-symbol table, otherwise the global symbol table is changed.
+symbol table; otherwise the global symbol table is changed.
=item Any other string
present only in some versions of the DECCRTL; check C<$Config{d_setenv}>
to see whether your copy of Perl was built with a CRTL that has this
function.)
-
+
When an element of C<%ENV> is set to C<undef>,
the element is looked up as if it were being read, and if it is
found, it is deleted. (An item "deleted" from the CRTL C<environ>
(You can't just say C<$ENV{$key} = $ENV{$key}>, since the
Perl optimizer is smart enough to elide the expression.)
+Don't try to clear C<%ENV> by saying C<%ENV = ();>, it will throw
+a fatal error. This is equivalent to doing the following from DCL:
+
+ DELETE/LOGICAL *
+
+You can imagine how bad things would be if, for example, the SYS$MANAGER
+or SYS$SYSTEM logicals were deleted.
+
At present, the first time you iterate over %ENV using
C<keys>, or C<values>, you will incur a time penalty as all
logical names are read, in order to fully populate %ENV.
You do need to be careful with the logicals representing process-permanent
files, such as C<SYS$INPUT> and C<SYS$OUTPUT>. 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
+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)
low order 8 bits of C<$?> are always 0 under VMS, since the
termination status of a process may or may not have been
generated by an exception. The next 8 bits are derived from
-severity portion of the subprocess' exit status: if the
+the severity portion of the subprocess' exit status: if the
severity was success or informational, these bits are all 0;
-otherwise, they contain the severity value shifted left one bit.
+if the severity was warning, they contain a value of 1; if the
+severity was error or fatal error, they contain the actual
+severity bits, which turns out to be a value of 2 for error
+and 4 for fatal error.
+
As a result, C<$?> will always be zero if the subprocess' exit
status indicated successful completion, and non-zero if a
-warning or error occurred. The actual VMS exit status may
-be found in C<$^S> (q.v.).
-
-=item $^S
-
-Under VMS, this is the 32-bit VMS status value returned by the
-last subprocess to complete. Unlink C<$?>, no manipulation
-is done to make this look like a POSIX wait(5) value, so it
-may be treated as a normal VMS status value.
+warning or error occurred. Conversely, when setting C<$?> in
+an END block, an attempt is made to convert the POSIX value
+into a native status intelligible to the operating system upon
+exiting Perl. What this boils down to is that setting C<$?>
+to zero results in the generic success value SS$_NORMAL, and
+setting C<$?> to a non-zero value results in the generic
+failure status SS$_ABORT. See also L<perlport/exit>.
+
+The pragma C<use vmsish 'status'> makes C<$?> reflect the actual
+VMS exit status instead of the default emulation of POSIX status
+described above. This pragma also disables the conversion of
+non-zero values to SS$_ABORT when setting C<$?> in an END
+block (but zero will still be converted to SS$_NORMAL).
=item $|
=head1 Revision date
-This document was last updated on 26-Feb-2000, for Perl 5,
-patchlevel 6.
+This document was last updated on 2-Oct-2001, for Perl 5,
+patchlevel 8.
=head1 AUTHOR
Charles Bailey <bailey@cor.newman.upenn.edu>
+Craig Berry <craigberry@mac.com>
Dan Sugalski <dan@sidhe.org>
https://perl5.git.perl.org / perl5.git / blobdiff