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
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
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<$?> in this document for more
+detail.
=item time
(You can't just say C<$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.
generated by an exception. The next 8 bits are derived from
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 $^S
-
-Under VMS, this is the 32-bit VMS status value returned by the
-last subprocess to complete. Unlike C<$?>, 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 7-Aug-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>