-=head1 Notes on Perl 5 for VMS
+=head1 NAME
+
+perlvms - VMS-specific documentation for Perl
+
+=head1 DESCRIPTION
Gathered below are notes describing details of Perl 5's
behavior on VMS. They are a supplement to the regular Perl 5
missed something you think should appear here, please don't
hesitate to drop a line to vmsperl@genetics.upenn.edu.
-=head1 Organization of Perl
+=head1 Installation
-=head2 Perl Images
+Directions for building and installing Perl 5 can be found in
+the file F<README.vms> in the main source directory of the
+Perl distribution..
+
+=head1 Organization of Perl Images
+
+=head2 Core Images
During the installation process, three Perl images are produced.
F<Miniperl.Exe> is an executable image which contains all of
Perl extensions are packages which provide both XS and Perl code
to add new functionality to perl. (XS is a meta-language which
simplifies writing C code which interacts with Perl, see
-L<perlapi> for more details.) The Perl code for an
+L<perlxs> for more details.) The Perl code for an
extension is treated like any other library module - it's
made available in your script through the appropriate
C<use> or C<require> statement, and usually defines a Perl
the C<MakeMaker> library modules supplied with Perl to generate
a F<Descrip.MMS> file for the extension.
-=head3 Installing static extensions
+=head2 Installing static extensions
Since static extensions are incorporated directly into
F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a
the library module for extension Foo::Bar would be copied
to a F<[.Foo.Bar]> subdirectory).
-=head3 Installic dynamic extensions
-
-First, you'll need to compile the XS code into a shareable image,
-either by hand or using the F<Descrip.MMS> supplied with the
-extension. If you're building the shareable image by hand, please
-note the following points:
- - The shareable image must be linked to F<PerlShr.Exe>, so it
- has access to Perl's global variables and routines. In
- order to specify the correct attributes for psects in
- F<PerlShr.Exe>, you should include the linker options file
- F<PerlShr_Attr.Opt> in the Link command. (This file is
- generated when F<PerlShr.Exe> is built, and is found in the
- main Perl source directory.
- - The entry point for the C<boot_>I<Extname> routine (where
- I<Extname> is the name of the extension, with all C<::>
- replaced by C<__>) must be a universal symbol. No other
- universal symbols are required to use the shareable image
- with Perl, though you may want to include additional
- universal symbols if you plan to share code or data among
- different extensions.
-The shareable image can be placed in any of several locations:
- - the F<[.Auto.>I<Extname>F<]> subdirectory of one of
- the directories in C<@INC>, where I<Extname> is the
- name of the extension, with each C<::> translated to C<.>
- (e.g. for extension Foo::Bar, you would use the
- F<[.Auto.Foo.Bar]> subdirectory), or
+=head2 Installing dynamic extensions
+
+In general, the distributed kit for a Perl extension includes
+a file named Makefile.PL, which is a Perl program which is used
+to create a F<Descrip.MMS> file which can be used to build and
+install the files required by the extension. The kit should be
+unpacked into a directory tree B<not> under the main Perl source
+directory, and the procedure for building the extension is simply
+
+ $ perl Makefile.PL ! Create Descrip.MMS
+ $ mmk ! Build necessary files
+ $ mmk test ! Run test code, if supplied
+ $ mmk install ! Install into public Perl tree
+
+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, you shouldn't nest the source directory
+too deeply in your directory structure, lest you eccedd 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
+the physical directory structure.)
+
+VMS support for this process in the current release of Perl
+is sufficient to handle most extensions. However, it does
+not yet recognize extra libraries required to build shareable
+images which are part of an extension, so these must be added
+to the linker options file for the extension by hand. For
+instance, if the F<PGPLOT> extension to Perl requires the
+F<PGPLOTSHR.EXE> shareable image in order to properly link
+the Perl extension, then the line C<PGPLOTSHR/Share> must
+be added to the linker options file F<PGPLOT.Opt> produced
+during the build process for the Perl extension.
+
+By default, the shareable image for an extension is placed
+F<[.lib.site_perl.auto>I<Arch>.I<Extname>F<]> directory of the
+installed Perl directory tree (where I<Arch> is F<VMS_VAX> or
+F<VMS_AXP>, and I<Extname> is the name of the extension, with
+each C<::> translated to C<.>). (See the MakeMaker documentation
+for more details on installation options for extensions.)
+However, it can be manually placed in any of several locations:
+ - the F<[.Lib.Auto.>I<Arch>I<$PVers>I<Extname>F<]> subdirectory
+ of one of the directories in C<@INC> (where I<PVers>
+ is the version of Perl you're using, as supplied in C<$]>,
+ with '.' converted to '_'), or
- one of the directories in C<@INC>, or
- a directory which the extensions Perl library module
passes to the DynaLoader when asking it to map
is the portion of the extension's name after the last C<::>, which
translates to the full file specification of the shareable image.
-Once you've got the shareable image set up, you should copy the
-extension's Perl library module to the appropriate library directory
-(see the section above on installing static extensions).
-
-=head1 Installation
-
-Directions for building and installing Perl 5 can be found in
-the file F<ReadMe.VMS> in the main source directory of the
-Perl distribution..
+=head1 File specifications
-=head1 File specifications
+=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 fle
-specfication. Filenames are, of course, still case-
-insensitive. For consistency, most Perl 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; Perl respects the case-
-sensitivity of OSs like Unix.)
+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, etc. If you find instances
+'/' 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.
-=head1 Command line redirection
+=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 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<t/*/*> 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 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
+"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.
+
+=head1 PERL5LIB and PERLLIB
+
+The PERL5LIB and PERLLIB logical names work as documented L<perl>,
+except that the element separator is '|' instead of ':'. The
+directory specifications may use either VMS or Unix syntax.
+
+=head1 Command line
+
+=head2 I/O redirection and backgrounding
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>,
command is run in the background as an asynchronous
subprocess.
-=head1 Pipes
+=head2 Command line switches
-Input and output pipes to Perl filehandles are supported; the
-"file name" is passed to lib$spawn() for asynchronous
-execution. You should be careful to close any pipes you have
-opened in a Perl script, lest you leave any "orphaned"
-subprocesses around when Perl exits.
+The following command line switches behave differently under
+VMS than described in L<perlrun>. Note also that in order
+to pass uppercase switches to Perl, you need to enclose
+them in double-quotes on the command line, since the CRTL
+downcases all unquoted strings.
-You may also use backticks to invoke a DCL subprocess, whose
-output is used as the return value of the expression. The
-string between the backticks is passed directly to lib$spawn
-as the command to execute. In this case, Perl will wait for
-the subprocess to complete before continuing.
+=over 4
-=head1 Wildcard expansion
+=item -i
-File specifications containing wildcards are allowed both on
-the command line and within Perl globs (e.g. <C<*.c>>). 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 C<-i> switch is present but no extension for a backup
+copy is given, then inplace editing creates a new version of
+a file; the existing copy is not deleted. (Note that if
+an extension is given, an existing file is renamed to the backup
+file, as is the case under other operating systems, so it does
+not remain as a previous version under the original filename.)
-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<t/*/*> 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.
-
-=head1 PERL5LIB and PERLLIB
+=item -S
-The PERL5LIB and PERLLIB logical names work as
-documented L<perl>, except that the element
-separator is '|' instead of ':'. The directory
-specifications may use either VMS or Unix syntax.
+If the C<-S> switch is present I<and> the script name does
+not contain a directory, then Perl translates the logical
+name DCL$PATH as a searchlist, using each translation as
+a directory in which to look for the script. In addition,
+if no file type is specified, Perl looks in each directory
+for a file matching the name specified, with a blank type,
+a type of F<.pl>, and a type of F<.com>, in that order.
-=head1 %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<home>,
-C<path>,C<term>, and C<user> return the CRTL "environment
-variables" of the same names. The key C<default> returns the
-current default device and directory specification.
+=item -u
-Setting an element of %ENV defines a supervisor-mode logical
-name in the process logical name table. C<Undef>ing or
-C<delete>ing an element of %ENV deletes the equivalent user-
-mode or supervisor-mode logical name from the process logical
-name table. If you use C<undef>, the %ENV element remains
-empty. If you use C<delete>, 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.
+The C<-u> switch causes the VMS debugger to be invoked
+after the Perl program is compiled, but before it has
+run. It does not create a core dump file.
-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.
+=back
=head1 Perl functions
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,
+ file tests*, abs, alarm, atan, backticks*, binmode*, bless,
caller, chdir, chmod, chown, chomp, chop, chr,
- close, closedir, cos, defined, delete, die, do,
- each, endpwent, eof, eval, exec*, exists, exit,
- exp, fileno, fork*, getc, getpwent*, getpwnam*,
- getpwuid*, 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,
+ close, closedir, cos, crypt*, defined, delete,
+ die, do, dump*, each, endpwent, eof, eval, exec*,
+ exists, exit, exp, fileno, fork*, getc, getlogin,
+ 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,
- rmdir, s///, scalar, seek, seekdir, select(internal)*,
- setpwent, 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, utime*, values, vec, wait,
- waitpid*, wantarray, warn, write, y///
+ 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,
+ telldir, tie, time, times*, tr///, uc, ucfirst, umask,
+ undef, unlink*, unpack, untie, unshift, use, utime*,
+ values, vec, wait, waitpid*, 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,
- getgrent, kill, getgrgid, getgrnam, setgrent,
- 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
+ chroot, dbmclose, dbmopen, fcntl, 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, truncate
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,
getnetent, getprotoent, getservent, sethostent,
setnetent, setprotoent, setservent, endhostent,
endnetent, endprotoent, endservent, getsockname,
- getsockopt, listen, recv, send, setsockopt,
- shutdown, socket
+ getsockopt, listen, recv, select(system call)*,
+ send, setsockopt, shutdown, socket
+=over 4
=item File tests
specification without an explicit directory (e.g. C<DUA1:>), as
well as if passed a directory.
+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
+extended file header of files on remote volumes, attempts to
+examine the ACL fail, and the file tests will return false,
+with C<$!> indicating that the file does not exist. You can
+use C<stat> on these files, since that checks UIC-based protection
+only, and then manually check the appropriate bits, as defined by
+your C compiler's F<stat.h>, in the mode value it returns, if you
+need an approximation of the file's protections.
+
+=item backticks
+
+Backticks create a subprocess, and pass the enclosed string
+to it for execution as a DCL command. Since the subprocess is
+created directly via C<lib$spawn()>, any valid DCL command string
+may be specified.
+
=item binmode FILEHANDLE
-The C<binmode> operator has no effect under VMS. It will
-return TRUE whenever called, but will not affect I/O
-operations on the filehandle given as its argument.
+The C<binmode> operator will attempt to insure that no translation
+of carriage control occurs on input from or output to this filehandle.
+Since this involves reopening the file and then restoring its
+file position indicator, if this function returns FALSE, the
+underlying filehandle may no longer point to an open file, or may
+point to a different position in the file than before C<binmode>
+was called.
+
+Note that C<binmode> is generally not necessary when using normal
+filehandles; it is provided so that you can control I/O to existing
+record-structured files when necessary. You can also use the
+C<vmsfopen> function in the VMS::Stdio extension to gain finer
+control of I/O to files and devices with different record structures.
+
+=item crypt PLAINTEXT, USER
+
+The C<crypt> operator uses the C<sys$hash_password> system
+service to generate the hashed representation of PLAINTEXT.
+If USER is a valid username, the algorithm and salt values
+are taken from that user's UAF record. If it is not, then
+the preferred algorithm and a salt of 0 are used. The
+quadword encrypted value is returned as an 8-character string.
+
+The value returned by C<crypt> may be compared against
+the encrypted password from the UAF returned by the C<getpw*>
+functions, in order to authenticate users. If you're
+going to do this, remember that the encrypted password in
+the UAF was generated using uppercase username and
+password strings; you'll have to upcase the arguments to
+C<crypt> to insure that you'll get the proper value:
+
+ sub validate_passwd {
+ my($user,$passwd) = @_;
+ my($pwdhash);
+ if ( !($pwdhash = (getpwnam($user))[1]) ||
+ $pwdhash ne crypt("\U$passwd","\U$name") ) {
+ intruder_alert($name);
+ }
+ return 1;
+ }
+
+=item dump
+
+Rather than causing Perl to abort and dump core, the C<dump>
+operator invokes the VMS debugger. If you continue to
+execute the Perl program under the debugger, control will
+be transferred to the label specified as the argument to
+C<dump>, or, if no label was specified, back to the
+beginning of the program. All other state of the program
+(I<e.g.> values of variables, open file handles) are not
+affected by calling C<dump>.
=item exec LIST
use the C<system> operator or piped filehandles instead.
=item getpwent
+
=item getpwnam
+
=item getpwuid
These operators obtain the information described in L<perlfunc>,
contains the owner field from the UAF record. The C<$quota>
item is not used.
+=item gmtime
+
+The C<gmtime> operator will function properly if you have a
+working CRTL C<gmtime()> routine, or if the logical name
+SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds
+which must be added to UTC to yield local time. (This logical
+name is defined automatically if you are running a version of
+VMS with built-in UTC support.) If neither of these cases is
+true, a warning message is printed, and C<undef> is returned.
+
+=item kill
+
+In most cases, C<kill> 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 $FORCEX, which is ignored by
+supervisor-mode images like DCL.)
+
+Also, negative signal values don't do anything special under
+VMS; they're just converted to the corresponding positive value.
+
+=item qx//
+
+See the entry on C<backticks> above.
+
+=item select (system call)
+
+If Perl was not built with socket support, the system call
+version of C<select> is not available at all. If socket
+support is present, then the system call version of
+C<select> functions only for file descriptors attached
+to sockets. It will not provide information about regular
+files or pipes, since the CRTL C<select()> routine does not
+provide this functionality.
+
=item stat EXPR
Since VMS keeps track of files according to a different scheme
The C<system> operator creates a subprocess, and passes its
arguments to the subprocess for execution as a DCL command.
-Since the subprocess is created directly via lib$spawn, any
+Since the subprocess is created directly via C<lib$spawn()>, any
valid DCL command string may be specified. If LIST consists
of the empty string, C<system> spawns an interactive DCL subprocess,
in the same fashion as typiing B<SPAWN> at the DCL prompt.
Perl waits for the subprocess to complete before continuing
-execution in the current process.
+execution in the current process. As described in L<perlfunc>,
+the return value of C<system> is a fake "status" which follows
+POSIX semantics; see the description of C<$?> 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<$^S> in the meantime).
+
+=item time
+
+The value returned by C<time> is the offset in seconds from
+01-JAN-1970 00:00:00 (just like the CRTL's times() routine), in order
+to make life easier for code coming in from the POSIX/Unix world.
=item times
C<VMS::Filespec::candelete> operator. For instance, in order
to delete only files to which you have delete access, you could
say something like
+
sub safe_unlink {
my($file,$num);
foreach $file (@_) {
}
$num;
}
-Finally, if C<unlink> has to change the file protection to
-delete the file, and you interrupt it in midstream, the file
-may be left intact, but with a changed ACL allowing you delete
-access.
+
+(or you could just use C<VMS::Stdio::remove>, if you've installed
+the VMS::Stdio extension distributed with Perl). If C<unlink> has to
+change the file protection to delete the file, and you interrupt it
+in midstream, the file may be left intact, but with a changed ACL
+allowing you delete access.
=item utime LIST
The FLAGS argument is ignored in all cases.
+=back
+
+=head1 Perl variables
+
+The following VMS-specific information applies to the indicated
+"special" Perl variables, in addition to the general information
+in L<perlvar>. Where there is a conflict, this infrmation
+takes precedence.
+
+=over 4
+
+=item %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. If you append a semicolon to the
+logical name, followed by an integer, that integer is
+used as the translation index for the logical name,
+so that you can look up successive values for search
+list logical names. For instance, if you say
+
+ $ Define STORY once,upon,a,time,there,was
+ $ perl -e "for ($i = 0; $i <= 6; $i++) " -
+ _$ -e "{ print $ENV{'story;'.$i},' '}"
+
+Perl will print C<ONCE UPON A TIME THERE WAS>.
+
+The %ENV keys C<home>, C<path>,C<term>, and C<user>
+return the CRTL "environment variables" of the same
+names, if these logical names are not defined. The
+key C<default> returns the current default device
+and directory specification, regardless of whether
+there is a logical name DEFAULT defined..
+
+Setting an element of %ENV defines a supervisor-mode logical
+name in the process logical name table. C<Undef>ing or
+C<delete>ing an element of %ENV deletes the equivalent user-
+mode or supervisor-mode logical name from the process logical
+name table. If you use C<undef>, the %ENV element remains
+empty. If you use C<delete>, 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. It is not possible
+at present to define a search list logical name via %ENV.
+
+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.
+Subsequent iterations will not reread logical names, so they
+won't be as slow, but they also won't reflect any changes
+to logical name tables caused by other programs. The C<each>
+operator is special: it returns each element I<already> in
+%ENV, but doesn't go out and look for more. Therefore, if
+you've previously used C<keys> or C<values>, you'll see all
+the logical names visible to your process, and if not, you'll
+see only the names you've looked up so far. (This is a
+consequence of the way C<each> is implemented now, and it
+may change in the future, so it wouldn't be a good idea
+to rely on it too much.)
+
+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.
+
+=item $!
+
+The string value of C<$!> is that returned by the CRTL's
+strerror() function, so it will include the VMS message for
+VMS-specific errors. The numeric value of C<$!> is the
+value of C<errno>, except if errno is EVMSERR, in which
+case C<$!> contains the value of vaxc$errno. Setting C<$!>
+always sets errno to the value specified. If this value is
+EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-NOMSG), so
+that the string value of C<$!> won't reflect the VMS error
+message from before C<$!> was set.
+
+=item $^E
+
+This variable provides direct access to VMS status values
+in vaxc$errno, which are often more specific than the
+generic Unix-style error messages in C<$!>. Its numeric value
+is the value of vaxc$errno, and its string value is the
+corresponding VMS message string, as retrieved by sys$getmsg().
+Setting C<$^E> sets vaxc$errno to the value specified.
+
+=item $?
+
+The "status value" returned in C<$?> is synthesized from the
+actual exit status of the subprocess in a way that approximates
+POSIX wait(5) semantics, in order to allow Perl programs to
+portably test for successful completion of subprocesses. The
+low order 8 bits of C<$?> are always 0 under VMS, since the
+termination status of a process may or may not have been
+generated by an exception. The next 8 bits are derived from
+severity portion of the subprocess' exit status: if the
+severity was success or informational, these bits are all 0;
+otherwise, they contain the severity value shifted left one bit.
+As a result, C<$?> 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.
+
+=item $|
+
+Setting C<$|> for an I/O stream causes data to be flushed
+all the way to disk on each write (I<i.e.> not just to
+the underlying RMS buffers for a file). In other words,
+it's equivalent to calling fflush() and fsync() from C.
+
+=back
+
=head1 Revision date
-This document was last updated on 16-Dec-1994, for Perl 5,
-patchlevel 0.
+This document was last updated on 28-Feb-1996, for Perl 5,
+patchlevel 2.
+
+=head1 AUTHOR
+
+Charles Bailey bailey@genetics.upenn.edu
+
projects / p5sagit/p5-mst-13.2.git / blobdiff