Re: [PATCH] perl573delta delinting

[p5sagit/p5-mst-13.2.git] / pod / perlvar.pod

diff --git a/pod/perlvar.pod b/pod/perlvar.pod
index 98bd657..258645e 100644 (file)
--- a/pod/perlvar.pod
+++ b/pod/perlvar.pod
@@ -769,6 +769,12 @@ The process number of the Perl running this script.  You should
 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 $UID
@@ -1003,11 +1009,17 @@ built, as determined during the configuration process.  The value
 is identical to C<$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
 
@@ -1150,8 +1162,52 @@ lexical scope.  See L<bytes>.
 
 =item $^X
 
-The name that the Perl binary itself was executed as, from C's C<argv[0]>.
-This may not be a full pathname, nor even necessarily in your path.
+The name used to execute the current copy of Perl, from C's
+C<argv[0]>.
+
+Depending on the host operating system, the value of $^X may be
+a relative or absolute pathname of the perl program file, or may
+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.  For VMS, the
+value may or may not include a version number.
+
+You usually can use the value of $^X to re-invoke an independent
+copy of the same perl that is currently running, e.g.,
+
+  @first_run = `$^X -le "print int rand 100 for 1..100"`;
+
+But recall that not all operating systems support forking or
+capturing of the output of commands, so this complex statement
+may not be portable.
+
+It is not safe to use the value of $^X as a path name of a file,
+as some operating systems that have a mandatory suffix on
+executable files do not require use of the suffix when invoking
+a command.  To convert the value of $^X to a path name, use the
+following statements:
+
+# Build up a set of file names (not command names).
+  use Config;
+  $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
+then execute the copy, the security-conscious Perl programmer
+should take care to invoke the installed copy of perl, not the
+copy referenced by $^X.  The following statements accomplish
+this goal, and produce a pathname that can be invoked as a
+command or referenced as a file.
+
+  use Config;
+  $secure_perl_path = $Config{perlpath};
+  if ($^O ne 'VMS')
+     {$secure_perl_path .= $Config{_exe}
+          unless $secure_perl_path =~ m/$Config{_exe}$/i;}
 
 =item ARGV
 
@@ -1175,6 +1231,13 @@ the script.  C<$#ARGV> is generally the number of arguments minus
 one, because C<$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
@@ -1410,8 +1473,9 @@ used safely in programs.  C<$^_> itself, however, I<is> reserved.
 
 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
@@ -1421,7 +1485,7 @@ other names are also exempt:
 
 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