I<N.B.> 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
+For this reason if you are running 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
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.)
+Perl is now in the process of evolving to follow the setting of
+the DECC$* feature logical names in the interpretation of UNIX pathnames.
+This is still a work in progress.
+
+For handling extended characters, and case sensitivity, as long as
+DECC$POSIX_COMPLIANT_PATHNAMES, DECC$FILENAME_UNIX_REPORT, and
+DECC$FILENAME_UNIX_ONLY are not set, then the older Perl behavior
+for conversions of file specifications from UNIX to VMS is followed,
+except that VMS paths with concealed rooted logical names are now
+translated correctly to UNIX paths.
+
+With those features set, then new routines may handle the translation,
+because some of the rules are different. The presence of ./.../
+in a UNIX path is no longer translated to the VMS [...]. It will
+translate to [.^.^.^.]. To be compatible with what MakeMaker expects,
+if a VMS path can not be translated to a UNIX path when unixify
+is called, it is passed through unchanged. So unixify("[...]") will
+return "[...]".
+
+The handling of extended characters will also be better with the
+newer translation routines. But more work is needed to fully support
+extended file syntax names. In particular, at this writing Pathtools
+can not deal with directories containing some extended characters.
+
+There are several ambiguous cases where a conversion routine can not
+determine if an input filename is in UNIX format or in VMS format,
+since now both VMS UNIX file specifications can have characters in
+them that could be mistaken for syntax delimiters of the other type.
+So some pathnames simply can not be used in a mode that allows either
+type of pathname to be present.
+
+Perl will tend to assume that an ambiguous filename is in UNIX format.
+
+Allowing "." as a version delimiter is simply incompatible with
+determining if a pathname is already VMS format or UNIX with the
+extended file syntax. There is no way to know if "perl-5.8.6" that
+TAR produces is a UNIX "perl-5.8.6" or a VMS "perl-5.8;6" when
+passing it to unixify() or vmsify().
+
+The DECC$FILENAME_UNIX_REPORT or the DECC$FILENAME_UNIX_ONLY logical
+names control how Perl interprets filenames.
+
+The DECC$FILENAME_UNIX_ONLY setting has not been tested at this time.
+Perl uses traditional OpenVMS file specifications internally and in
+the test harness, so this mode may have limited use, or require more
+changes to make usable.
+
+Everything about DECC$FILENAME_UNIX_REPORT should be assumed to apply
+to DECC$FILENAME_UNIX_ONLY mode. The DECC$FILENAME_UNIX_ONLY differs
+in that it expects all filenames passed to the C runtime to be already
+in UNIX format.
+
+Again, currently most of the core Perl modules have not yet been updated
+to understand that VMS is not as limited as it use to be. Fixing that
+is a work in progress.
+
+The logical name DECC$POSIX_COMPLIANT_PATHNAMES is new with the
+RMS Symbolic Link SDK. This version of Perl does not support it being set.
+
+
+Filenames are case-insensitive on VAX, and on ODS-2 formatted
+volumes on ALPHA and I64.
+
+On ODS-5 volumes filenames are case preserved and on newer
+versions of OpenVMS can be optionally case sensitive.
+
+On ALPHA and I64, Perl is in the process of being changed to follow the
+process case sensitivity setting to report if the file system is case
+sensitive.
+
+Perl programs should not assume that VMS is case blind, or that
+filenames will be in lowercase.
+
+Programs should use the File::Spec:case_tolerant setting to determine
+the state, and not the $^O setting.
+
+For consistency, when the above feature is clear and when not
+otherwise overridden by DECC feature logical names, most Perl routines
+return file specifications using lower case letters only,
+regardless of the case used in the arguments passed to them.
+(This is true only when running under VMS; Perl respects the
+case-sensitivity of OSs like Unix.)
We've tried to minimize the dependence of Perl library
modules on Unix syntax, but you may find that some of these,
of this in the Perl distribution itself, please let us know,
so we can try to work around them.
+Also when working on Perl programs on VMS, if you need a syntax
+in a specific operating system format, then you need to either
+check the appropriate DECC$ feature logical, or call a conversion
+routine to force it to that format.
+
=head2 Wildcard expansion
File specifications containing wildcards are allowed both on
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
except that the element separator is '|' instead of ':'. The
directory specifications may use either VMS or Unix syntax.
+=head1 The Perl Forked Debugger
+
+The Perl forked debugger places the debugger commands and output in a
+separate X-11 terminal window so that commands and output from multiple
+processes are not mixed together.
+
+Perl on VMS supports an emulation of the forked debugger when Perl is
+run on a VMS system that has X11 support installed.
+
+To use the forked debugger, you need to have the default display set to an
+X-11 Server and some environment variables set that Unix expects.
+
+The forked debugger requires the environment variable C<TERM> to be C<xterm>,
+and the environment variable C<DISPLAY> to exist. C<xterm> must be in
+lower case.
+
+ $define TERM "xterm"
+
+ $define DISPLAY "hostname:0.0"
+
+Currently the value of C<DISPLAY> is ignored. It is recommended that it be set
+to be the hostname of the display, the server and screen in UNIX notation. In
+the future the value of DISPLAY may be honored by Perl instead of using the
+default display.
+
+It may be helpful to always use the forked debugger so that script I/O is
+separated from debugger I/O. You can force the debugger to be forked by
+assigning a value to the logical name <PERLDB_PIDS> that is not a process
+identification number.
+
+ $define PERLDB_PIDS XXXX
+
+
+=head1 PERL_VMS_EXCEPTION_DEBUG
+
+The PERL_VMS_EXCEPTION_DEBUG being defined as "ENABLE" will cause the VMS
+debugger to be invoked if a fatal exception that is not otherwise
+handled is raised. The purpose of this is to allow debugging of
+internal Perl problems that would cause such a condition.
+
+This allows the programmer to look at the execution stack and variables to
+find out the cause of the exception. As the debugger is being invoked as
+the Perl interpreter is about to do a fatal exit, continuing the execution
+in debug mode is usally not practical.
+
+Starting Perl in the VMS debugger may change the program execution
+profile in a way that such problems are not reproduced.
+
+The C<kill> function can be used to test this functionality from within
+a program.
+
+In typical VMS style, only the first letter of the value of this logical
+name is actually checked in a case insensitive mode, and it is considered
+enabled if it is the value "T","1" or "E".
+
+This logical name must be defined before Perl is started.
+
=head1 Command line
=head2 I/O redirection and backgrounding
them in double-quotes on the command line, since the CRTL
downcases all unquoted strings.
+On newer 64 bit versions of OpenVMS, a process setting now
+controls if the quoting is needed to preserve the case of
+command line arguments.
+
=over 4
=item -i
getsockopt, listen, recv, select(system call)*,
send, setsockopt, shutdown, socket
+The following function is available on Perls built on 64 bit OpenVMS 8.2
+with hard links enabled on an ODS-5 formatted build disk. If someone with
+an OpenVMS 7.3-1 system were to modify configure.com and test the results,
+this feature can be brought back to OpenVMS 7.3-1 and later. Hardlinks
+must be enabled on the build disk because if the build procedure sees
+this feature enabled, it uses it.
+
+ link
+
+The following functions are available on Perls built on 64 bit OpenVMS
+8.2 and can be implemented on OpenVMS 7.3-2 if someone were to modify
+configure.com and test the results. (While in the build, at the time
+of this writing, they have not been specifically tested.)
+
+ getgrgid, getgrnam, getpwnam, getpwuid,
+ setgrent, ttyname
+
+The following functions are available on Perls built on 64 bit OpenVMS 8.2
+and later. (While in the build, at the time of this writing, they have
+not been specifically tested.)
+
+ statvfs, socketpair
+
+The following functions are expected to soon be available on Perls built
+on 64 bit OpenVMS 8.2 or later with the RMS Symbolic link package. Use
+of symbolic links at this time effectively requires the
+DECC$POSIX_COMPLIANT_PATHNAMES to defined as 3, and operating in a
+DECC$FILENAME_UNIX_REPORT mode.
+
+ lchown, link, lstat, readlink, symlink
+
=over 4
=item File tests
specification without an explicit directory (e.g. C<DUA1:>), as
well as if passed a directory.
+There are DECC feature logical names AND ODS-5 volume attributes that
+also control what values are returned for the date fields.
+
Note: Some sites have reported problems when using the file-access
tests (C<-r>, C<-w>, and C<-x>) on files accessed via DEC's DFS.
Specifically, since DFS does not currently provide access to the
return 1;
}
+
+=item die
+
+C<die> will force the native VMS exit status to be an SS$_ABORT code
+if neither of the $! or $? status values are ones that would cause
+the native status to be interpreted as being what VMS classifies as
+SEVERE_ERROR severity for DCL error handling.
+
+When the future POSIX_EXIT mode is active, C<die>, the native VMS exit
+status value will have either one of the C<$!> or C<$?> or C<$^E> or
+the UNIX value 255 encoded into it in a way that the effective original
+value can be decoded by other programs written in C, including Perl
+and the GNV package. As per the normal non-VMS behavior of C<die> if
+either C<$!> or C<$?> are non-zero, one of those values will be
+encoded into a native VMS status value. If both of the UNIX status
+values are 0, and the C<$^E> value is set one of ERROR or SEVERE_ERROR
+severity, then the C<$^E> value will be used as the exit code as is.
+If none of the above apply, the UNIX value of 255 will be encoded into
+a native VMS exit status value.
+
+Please note a significant difference in the behavior of C<die> in
+the future POSIX_EXIT mode is that it does not force a VMS
+SEVERE_ERROR status on exit. The UNIX exit values of 2 through
+255 will be encoded in VMS status values with severity levels of
+SUCCESS. The UNIX exit value of 1 will be encoded in a VMS status
+value with a severity level of ERROR. This is to be compatible with
+how the VMS C library encodes these values.
+
+The minimum severity level set by C<die> in a future POSIX_EXIT mode
+may be changed to be ERROR or higher before that mode becomes fully active
+depending on the results of testing and further review. If this is
+done, the behavior of c<DIE> in the future POSIX_EXIT will close enough
+to the default mode that most DCL shell scripts will probably not notice
+a difference.
+
+See C<$?> for a description of the encoding of the UNIX value to
+produce a native VMS status containing it.
+
+
=item dump
Rather than causing Perl to abort and dump core, the C<dump>
in midstream, the file may be left intact, but with a changed ACL
allowing you delete access.
+This behavior of C<unlink> is to be compatible with POSIX behavior
+and not traditional VMS behavior.
+
=item utime LIST
-Since ODS-2, the VMS file structure for disk files, does not keep
-track of access times, this operator changes only the modification
-time of the file (VMS revision date).
+This operator changes only the modification time of the file (VMS
+revision date) on ODS-2 volumes and ODS-5 volumes without access
+dates enabled. On ODS-5 volumes with access dates enabled, the
+true access time is modified.
=item waitpid PID,FLAGS
DELETE/LOGICAL *
You can imagine how bad things would be if, for example, the SYS$MANAGER
-or SYS$SYSTEM logicals were deleted.
+or SYS$SYSTEM logical names 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
won't be as slow, but they also won't reflect any changes
to logical name tables caused by other programs.
-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
-possible to get the values of these logicals, as the null byte acted as an
-end-of-string marker)
+You do need to be careful with the logical names representing
+process-permanent files, such as C<SYS$INPUT> and C<SYS$OUTPUT>.
+The translations for these logical names are prepended with a
+two-byte binary value (0x1B 0x00) that needs to be stripped off
+if you wantto use it. (In previous versions of Perl it wasn't
+possible to get the values of these logical names, as the null
+byte acted as an end-of-string marker)
=item $!
corresponding VMS message string, as retrieved by sys$getmsg().
Setting C<$^E> sets vaxc$errno to the value specified.
+While Perl attempts to keep the vaxc$errno value to be current, if
+errno is not EVMSERR, it may not be from the current operation.
+
=item $?
The "status value" returned in C<$?> is synthesized from the
portably test for successful completion of subprocesses. The
low order 8 bits of C<$?> are always 0 under VMS, since the
termination status of a process may or may not have been
-generated by an exception. The next 8 bits are derived from
-the severity portion of the subprocess' exit status: if the
-severity was success or informational, these bits are all 0;
-if the severity was warning, they contain a value of 1; if the
-severity was error or fatal error, they contain the actual
-severity bits, which turns out to be a value of 2 for error
-and 4 for fatal error.
+generated by an exception.
+
+The next 8 bits contain the termination status of the program.
+
+If the child process follows the convention of C programs
+compiled with the _POSIX_EXIT macro set, the status value will
+contain the actual value of 0 to 255 returned by that program
+on a normal exit.
+
+With the _POSIX_EXIT macro set, the UNIX exit value of zero is
+represented as a VMS native status of 1, and the UNIX values
+from 2 to 255 are encoded by the equation:
+
+ VMS_status = 0x35a000 + (unix_value * 8) + 1.
+
+And in the special case of unix value 1 the encoding is:
+
+ VMS_status = 0x35a000 + 8 + 2 + 0x10000000.
+
+For other termination statuses, the severity portion of the
+subprocess' exit status is used: if the severity was success or
+informational, these bits are all 0; if the severity was
+warning, they contain a value of 1; if the severity was
+error or fatal error, they contain the actual severity bits,
+which turns out to be a value of 2 for error and 4 for severe_error.
+Fatal is another term for the severe_error status.
As a result, C<$?> will always be zero if the subprocess' exit
status indicated successful completion, and non-zero if a
-warning or error occurred. 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>.
+warning or error occurred or a program compliant with encoding
+_POSIX_EXIT values was run and set a status.
+
+How can you tell the difference between a non-zero status that is
+the result of a VMS native error status or an encoded UNIX status?
+You can not unless you look at the ${^CHILD_ERROR_NATIVE} value.
+The ${^CHILD_ERROR_NATIVE} value returns the actual VMS status value
+and check the severity bits. If the severity bits are equal to 1,
+then if the numeric value for C<$?> is between 2 and 255 or 0, then
+C<$?> accurately reflects a value passed back from a UNIX application.
+If C<$?> is 1, and the severity bits indicate a VMS error (2), then
+C<$?> is from a UNIX application exit value.
+
+In practice, Perl scripts that call programs that return _POSIX_EXIT
+type status values will be expecting those values, and programs that
+call traditional VMS programs will either be expecting the previous
+behavior or just checking for a non-zero status.
+
+And success is always the value 0 in all behaviors.
+
+When the actual VMS termination status of the child is an error,
+internally the C<$!> value will be set to the closest UNIX errno
+value to that error so that Perl scripts that test for error
+messages will see the expected UNIX style error message instead
+of a VMS message.
+
+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$_ABORT. See also L<perlport/exit>.
+
+With the future POSIX_EXIT mode set, setting C<$?> will cause the
+new value to also be encoded into C<$^E> so that the either the
+original parent or child exit status values of 0 to 255
+can be automatically recovered by C programs expecting _POSIX_EXIT
+behavior. If both a parent and a child exit value are non-zero, then it
+will be assumed that this is actually a VMS native status value to
+be passed through. The special value of 0xFFFF is almost a NOOP as
+it will cause the current native VMS status in the C library to
+become the current native Perl VMS status, and is handled this way
+as consequence of it known to not be a valid native VMS status value.
+It is recommend that only values in range of normal UNIX parent or
+child status numbers, 0 to 255 are used.
The pragma C<use vmsish 'status'> makes C<$?> reflect the actual
VMS exit status instead of the default emulation of POSIX status
non-zero values to SS$_ABORT when setting C<$?> in an END
block (but zero will still be converted to SS$_NORMAL).
+Do not use the pragma C<use vmsish 'status'> with the future
+POSIX_EXIT mode, as they are at times requesting conflicting
+actions and the consequence of ignoring this advice will be
+undefined to allow future improvements in the POSIX exit handling.
+
=item $|
Setting C<$|> for an I/O stream causes data to be flushed
=head1 Revision date
-This document was last updated on 01-May-2002, for Perl 5,
+This document was last updated on 14-Oct-2005, for Perl 5,
patchlevel 8.
=head1 AUTHOR
Charles Bailey bailey@cor.newman.upenn.edu
Craig Berry craigberry@mac.com
Dan Sugalski dan@sidhe.org
+John Malmberg wb8tyw@qsl.net
https://perl5.git.perl.org / perl5.git / blobdiff