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
=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<e.g.> 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<VMS::Filespec> 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<etc.> If you find instances
-of this in the Perl distribution itself, please let us know,
-so we can try to work around them.
+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<e.g.> 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<VMS::Filespec> package for explicit interconversion between VMS and
+Unix syntax; its documentation provides more details.
+
+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<etc.> If you find instances
+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 either to
+check the appropriate DECC$ feature logical, or call a conversion
+routine to force it to that format.
+
+The feature logical name DECC$FILENAME_UNIX_REPORT modifies traditional
+Perl behavior in the conversion of file specifications from Unix to VMS
+format in order to follow the extended character handling rules now
+expected by the CRTL. Specifically, when this feature is in effect, the
+C<./.../> in a Unix path is now translated to C<[.^.^.^.]> instead of
+the traditional VMS C<[...]>. To be compatible with what MakeMaker
+expects, if a VMS path cannot be translated to a Unix path, it is
+passed through unchanged, so C<unixify("[...]")> will return C<[...]>.
+
+The handling of extended characters is largely complete in the
+VMS-specific C infrastructure of Perl, but more work is still needed to
+fully support extended syntax filenames in several core modules. In
+particular, at this writing PathTools has only partial support for
+directories containing some extended characters.
+
+There are several ambiguous cases where a conversion routine cannot
+determine whether an input filename is in Unix format or in VMS format,
+since now both VMS and Unix file specifications may have characters in
+them that could be mistaken for syntax delimiters of the other type. So
+some pathnames simply cannot be used in a mode that allows either type
+of pathname to be present. Perl will tend to assume that an ambiguous
+filename is in Unix format.
+
+Allowing "." as a version delimiter is simply incompatible with
+determining whether a pathname is in VMS format or in Unix format with
+extended file syntax. There is no way to know whether "perl-5.8.6" is a
+Unix "perl-5.8.6" or a VMS "perl-5.8;6" when passing it to unixify() or
+vmsify().
+
+The DECC$FILENAME_UNIX_REPORT logical name controls how Perl interprets
+filenames to the extent that Perl uses the CRTL internally for many
+purposes, and attempts to follow CRTL conventions for reporting
+filenames. The DECC$FILENAME_UNIX_ONLY feature differs in that it
+expects all filenames passed to the C run-time to be already in Unix
+format. This feature is not yet supported in Perl since Perl uses
+traditional OpenVMS file specifications internally and in the test
+harness, and it is not yet clear whether this mode will be useful or
+useable. The feature logical name DECC$POSIX_COMPLIANT_PATHNAMES is new
+with the RMS Symbolic Link SDK and included with OpenVMS v8.3, but is
+not yet supported in Perl.
+
+=head2 Filename Case
+
+Perl follows VMS defaults and override settings in preserving (or not
+preserving) filename case. Case is not preserved on ODS-2 formatted
+volumes on any architecture. On ODS-5 volumes, filenames may be case
+preserved depending on process and feature settings. Perl now honors
+DECC$EFS_CASE_PRESERVE and DECC$ARGV_PARSE_STYLE on those systems where
+the CRTL supports these features. When these features are not enabled
+or the CRTL does not support them, Perl follows the traditional CRTL
+behavior of downcasing command-line arguments and returning file
+specifications in lower case only.
+
+I<N. B.> It is very easy to get tripped up using a mixture of other
+programs, external utilities, and Perl scripts that are in varying
+states of being able to handle case preservation. For example, a file
+created by an older version of an archive utility or a build utility
+such as MMK or MMS may generate a filename in all upper case even on an
+ODS-5 volume. If this filename is later retrieved by a Perl script or
+module in a case preserving environment, that upper case name may not
+match the mixed-case or lower-case exceptions of the Perl code. Your
+best bet is to follow an all-or-nothing approach to case preservation:
+either don't use it at all, or make sure your entire toolchain and
+application environment support and use it.
+
+OpenVMS Alpha v7.3-1 and later and all version of OpenVMS I64 support
+case sensitivity as a process setting (see C<SET PROCESS
+/CASE_LOOKUP=SENSITIVE>). Perl does not currently support case
+sensitivity on VMS, but it may in the future, so Perl programs should
+use the C<< File::Spec->case_tolerant >> method to determine the state, and
+not the C<$^O> variable.
+
+=head2 Symbolic Links
+
+When built on an ODS-5 volume with symbolic links enabled, Perl by
+default supports symbolic links when the requisite support is available
+in the filesystem and CRTL (generally 64-bit OpenVMS v8.3 and later).
+There are a number of limitations and caveats to be aware of when
+working with symbolic links on VMS. Most notably, the target of a valid
+symbolic link must be expressed as a Unix-style path and it must exist
+on a volume visible from your POSIX root (see the C<SHOW ROOT> command
+in DCL help). For further details on symbolic link capabilities and
+requirements, see chapter 12 of the CRTL manual that ships with OpenVMS
+v8.3 or later.
=head2 Wildcard expansion
Similarly, the resultant filespec will contain the file version
only if one was present in the input filespec.
+
=head2 Pipes
Input and output pipes to Perl filehandles are supported; the
Perl will wait for the subprocess to complete before continuing.
The mailbox (MBX) that perl can create to communicate with a pipe
-defaults to a buffer size of 512. The default buffer size is
-adjustable via the logical name PERL_MBX_SIZE provided that the
-value falls between 128 and the SYSGEN parameter MAXBUF inclusive.
-For example, to double the MBX size from the default within
-a Perl program, use C<$ENV{'PERL_MBX_SIZE'} = 1024;> and then
-open and use pipe constructs. An alternative would be to issue
-the command:
+defaults to a buffer size of 8192 on 64-bit systems, 512 on VAX. 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 set the mailbox size to 32767 use
+C<$ENV{'PERL_MBX_SIZE'} = 32767;> and then open and use pipe constructs.
+An alternative would be to issue the command:
- $ Define PERL_MBX_SIZE 1024
+ $ Define PERL_MBX_SIZE 32767
before running your wide record pipe program. A larger value may
improve performance at the expense of the BYTLM UAF quota.
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 usually 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
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,
+ close, closedir, cos, crypt*, defined, delete, die, do, dump*,
+ each, endgrent, endpwent, eof, eval, exec*, exists, exit, exp,
+ fileno, flock getc, getgrent*, getgrgid*, getgrnam, getlogin,
+ getppid, getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto,
+ grep, hex, ioctl, import, index, int, join, keys, kill*,
+ last, lc, lcfirst, lchown*, length, link*, local, localtime, log,
+ lstat, 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, readlink*, 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,
+ select (system call)*, setgrent, setpwent, shift, sin, sleep,
+ socketpair, sort, splice, split, sprintf, sqrt, srand, stat,
+ study, substr, symlink*, 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///
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,
+ chroot, dbmclose, dbmopen, fork*, getpgrp, getpriority,
+ msgctl, msgget, msgsend, msgrcv, semctl,
semget, semop, setpgrp, setpriority, shmctl, shmget,
- shmread, shmwrite, socketpair, symlink, syscall
+ shmread, shmwrite, syscall
The following functions are available on Perls compiled with Dec C
5.2 or greater and running VMS 7.0 or greater:
getsockopt, listen, recv, select(system call)*,
send, setsockopt, shutdown, socket
+The following function is available on Perls built on 64 bit OpenVMS v8.2
+with hard links enabled on an ODS-5 formatted build disk. CRTL support
+is in principle available as of OpenVMS v7.3-1, and better configuration
+support could detect this.
+
+ link
+
+The following functions are available on Perls built on 64 bit OpenVMS
+v8.2 and later. CRTL support is in principle available as of OpenVMS
+v7.3-2, and better configuration support could detect this.
+
+ getgrgid, getgrnam, getpwnam, getpwuid,
+ setgrent, ttyname
+
+The following functions are available on Perls built on 64 bit OpenVMS v8.2
+and later.
+
+ statvfs, socketpair
+
=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 $? status values are ones that would cause
+the native status to be interpreted as being what VMS classifies as
+SEVERE_ERROR severity for DCL error handling.
+
+When C<PERL_VMS_POSIX_EXIT> is active (see L</"$?"> below), 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<$^E> value will be used as the exit code as is.
+If none of the above apply, the Unix value of 255 will be encoded into
+a native VMS exit status value.
+
+Please note a significant difference in the behavior of C<die> in
+the C<PERL_VMS_POSIX_EXIT> mode is that it does not force a VMS
+SEVERE_ERROR status on exit. The Unix exit values of 2 through
+255 will be encoded in VMS status values with severity levels of
+SUCCESS. The Unix exit value of 1 will be encoded in a VMS status
+value with a severity level of ERROR. This is to be compatible with
+how the VMS C library encodes these values.
+
+The minimum severity level set by C<die> in C<PERL_VMS_POSIX_EXIT> mode
+may be changed to be ERROR or higher in the future depending on the
+results of testing and further review.
+
+See L</"$?"> 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>
=item 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
-process is actually deleted, if at all possible. (The CRTL's C<kill()>
-function is presently implemented via $FORCEX, which is ignored by
-supervisor-mode images like DCL.)
+In most cases, C<kill> is implemented via the undocumented system
+service C<$SIGPRC>, which has the same calling sequence as C<$FORCEX>, but
+throws an exception in the target process rather than forcing it to call
+C<$EXIT>. Generally speaking, C<kill> follows the behavior of the
+CRTL's C<kill()> function, but unlike that function can be called from
+within a signal handler. Also, unlike the C<kill> in some versions of
+the CRTL, Perl's C<kill> checks the validity of the signal passed in and
+returns an error rather than attempting to send an unrecognized signal.
Also, negative signal values don't do anything special under
VMS; they're just converted to the corresponding positive value.
there is no difference between "user time" and "system" time
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
+whether C<times()> keeps track of subprocesses separately. Note
especially that the VAXCRTL (at least) keeps track only of
-subprocesses spawned using L<fork> and L<exec>; it will not
-accumulate the times of subprocesses spawned via pipes, L<system>,
+subprocesses spawned using C<fork()> and C<exec()>; it will not
+accumulate the times of subprocesses spawned via pipes, C<system()>,
or backticks.
=item unlink LIST
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
=item CRTL_ENV
-This string tells Perl to consult the CRTL's internal C<environ>
-array of key-value pairs, using I<name> as the key. In most cases,
-this contains only a few keys, but if Perl was invoked via the C
-C<exec[lv]e()> function, as is the case for CGI processing by some
-HTTP servers, then the C<environ> array may have been populated by
-the calling program.
+This string tells Perl to consult the CRTL's internal C<environ> array
+of key-value pairs, using I<name> as the key. In most cases, this
+contains only a few keys, but if Perl was invoked via the C
+C<exec[lv]e()> function, as is the case for some embedded Perl
+applications or when running under a shell such as GNV bash, the
+C<environ> array may have been populated by the calling program.
=item CLISYM_[LOCAL]
you make while Perl is running do not affect the behavior of C<%ENV>.
If F<PERL_ENV_TABLES> is not defined, then Perl defaults to consulting
first the logical name tables specified by F<LNM$FILE_DEV>, and then
-the CRTL C<environ> array.
+the CRTL C<environ> array. This default order is reversed when the
+logical name F<GNV$UNIX_SHELL> is defined, such as when running under
+GNV bash.
In all operations on %ENV, the key string is treated as if it
were entirely uppercase, regardless of the case actually
(The same is done if an existing logical name was defined in
executive or kernel mode; an existing user or supervisor mode
logical name is reset to the new value.) If the value is an empty
-string, the logical name's translation is defined as a single NUL
-(ASCII 00) character, since a logical name cannot translate to a
+string, the logical name's translation is defined as a single C<NUL>
+(ASCII C<\0>) character, since a logical name cannot translate to a
zero-length string. (This restriction does not apply to CLI symbols
or CRTL C<environ> values; they are set to the empty string.)
-An element of the CRTL C<environ> array can be set only if your
-copy of Perl knows about the CRTL's C<setenv()> function. (This is
-present only in some versions of the DECCRTL; check C<$Config{d_setenv}>
-to see whether your copy of Perl was built with a CRTL that has this
-function.)
-
-When an element of C<%ENV> is set to C<undef>,
-the element is looked up as if it were being read, and if it is
-found, it is deleted. (An item "deleted" from the CRTL C<environ>
-array is set to the empty string; this can only be done if your
-copy of Perl knows about the CRTL C<setenv()> function.) Using
-C<delete> to remove an element from C<%ENV> has a similar effect,
-but after the element is deleted, another attempt is made to
-look up the element, so an inner-mode logical name or a name in
-another location will replace the logical name just deleted.
-In either case, only the first value found searching PERL_ENV_TABLES
-is altered. It is not possible at present to define a search list
+
+When an element of C<%ENV> is set to C<undef>, the element is looked
+up as if it were being read, and if it is found, it is deleted. (An
+item "deleted" from the CRTL C<environ> array is set to the empty
+string.) Using C<delete> to remove an element from C<%ENV> has a
+similar effect, but after the element is deleted, another attempt is
+made to look up the element, so an inner-mode logical name or a name
+in another location will replace the logical name just deleted. In
+either case, only the first value found searching PERL_ENV_TABLES is
+altered. It is not possible at present to define a search list
logical name via %ENV.
The element C<$ENV{DEFAULT}> is special: when read, it returns
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 want to 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<$?> are always 0 under VMS, since the
termination status of a process may or may not have been
-generated by an exception. The next 8 bits are derived from
-the severity portion of the subprocess' exit status: if the
-severity was success or informational, these bits are all 0;
-if the severity was warning, they contain a value of 1; if the
-severity was error or fatal error, they contain the actual
-severity bits, which turns out to be a value of 2 for error
-and 4 for fatal error.
-
-As a result, C<$?> will always be zero if the subprocess' exit
+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's 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<$?> will always be zero if the subprocess's exit
status indicated successful completion, and non-zero if a
-warning or error occurred. Conversely, when setting C<$?> 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$_ABORT. See also L<perlport/exit>.
+
+With the C<PERL_VMS_POSIX_EXIT> logical name defined as "ENABLE",
+setting C<$?> will cause the new value to be encoded into C<$^E>
+so that either the original parent or child exit status values
+ 0 to 255 can be automatically recovered by C programs expecting
+_POSIX_EXIT behavior. If both a parent and a child exit value are
+non-zero, then it will be assumed that this is actually a VMS native
+status value to be passed through. The special value of 0xFFFF is
+almost a NOOP as it will cause the current native VMS status in the
+C library to become the current native Perl VMS status, and is handled
+this way as it is known to not be a valid native VMS status value.
+It is recommend that only values in the range of normal Unix parent or
+child status numbers, 0 to 255 are used.
The pragma C<use vmsish 'status'> makes C<$?> 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$_NORMAL).
+Do not use the pragma C<use vmsish 'status'> with C<PERL_VMS_POSIX_EXIT>
+enabled, as they are at times requesting conflicting actions and the
+consequence of ignoring this advice will be undefined to allow future
+improvements in the POSIX exit handling.
+
+In general, with C<PERL_VMS_POSIX_EXIT> enabled, more detailed information
+will be available in the exit status for DCL scripts or other native VMS tools,
+and will give the expected information for Posix programs. It has not been
+made the default in order to preserve backward compatibility.
+
+N.B. Setting C<DECC$FILENAME_UNIX_REPORT> implicitly enables
+C<PERL_VMS_POSIX_EXIT>.
+
=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,
-patchlevel 8.
+Please see the git repository for revision history.
=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