consider this variable read-only, although it will be altered
across fork() calls. (Mnemonic: same as shells.)
+Note for Linux users: on Linux, the C functions C<getpid()> and
+C<getppid()> return different values from different threads. In order to
+be portable, this behavior is not reflected by C<$$>, whose value remains
+consistent across threads. If you want to call the underlying C<getpid()>,
+you may use the CPAN module C<Linux::Pid>.
+
=item $REAL_USER_ID
=item $UID
is identical to C<$Config{'osname'}>. See also L<Config> and the
B<-V> command-line switch documented in L<perlrun>.
+In Windows platforms, $^O is not very helpful: since it is always
+C<MSWin32>, it doesn't tell the difference between
+95/98/ME/NT/2000/XP/CE/.NET. Use Win32::GetOSName() or
+Win32::GetOSVersion() (see L<Win32> and L<perlport>) to distinguish
+between the variants.
+
=item ${^OPEN}
An internal variable used by PerlIO. A string in two parts, separated
-by a C<\0> byte, the first part is the input disciplines, the second
-part is the output disciplines.
+by a C<\0> byte, the first part describes the input layers, the second
+part describes the output layers.
=item $PERLDB
be the string used to invoke perl but not the pathname of the
perl program file. Also, most operating systems permit invoking
programs that are not in the PATH environment variable, so there
-is no guarantee that the value of $^X is in PATH.
+is no guarantee that the value of $^X is in PATH. For VMS, the
+value may or may not include a version number.
You usually can use the value of $^X to re-invoke an independent
copy of the same perl that is currently running, e.g.,
# Build up a set of file names (not command names).
use Config;
- use File::Spec;
- $this_perl = File::Spec->canonpath($^X);
- $this_perl .= $Config{exe_ext}
- unless $this_perl =~ m/$Config{exe_ext}$/i;
+ $this_perl = $^X;
+ if ($^O ne 'VMS')
+ {$this_perl .= $Config{_exe}
+ unless $this_perl =~ m/$Config{_exe}$/i;}
Because many operating systems permit anyone with read access to
the Perl program file to make a copy of it, patch the copy, and
command or referenced as a file.
use Config;
- use File::Spec;
- $secure_perl_path = File::Spec->canonpath($Config{perlpath});
- $secure_perl_path .= $Config{exe_ext}
- unless $secure_perl_path =~ m/$Config{exe_ext}$/i;
+ $secure_perl_path = $Config{perlpath};
+ if ($^O ne 'VMS')
+ {$secure_perl_path .= $Config{_exe}
+ unless $secure_perl_path =~ m/$Config{_exe}$/i;}
=item ARGV
one, because C<$ARGV[0]> is the first argument, I<not> the program's
command name itself. See C<$0> for the command name.
+=item ARGVOUT
+
+The special filehandle that points to the currently open output file
+when doing edit-in-place processing with B<-i>. Useful when you have
+to do a lot of inserting and don't want to keep modifying $_. See
+L<perlrun> for the B<-i> switch.
+
=item @F
The array @F contains the fields of each line read in when autosplit
Perl identifiers that begin with digits, control characters, or
punctuation characters are exempt from the effects of the C<package>
-declaration and are always forced to be in package C<main>. A few
-other names are also exempt:
+declaration and are always forced to be in package C<main>; they are
+also exempt from C<strict 'vars'> errors. A few other names are also
+exempt in these ways:
ENV STDIN
INC STDOUT
In particular, the new special C<${^_XYZ}> variables are always taken
to be in package C<main>, regardless of any C<package> declarations
-presently in scope.
+presently in scope.
=head1 BUGS