The joy of $0. Undoing the #16399 makes Andreas'

tests (see [perl #22811]) pass (yes, padding with space	instead
of nul makes no sense, but that seems to work, maybe Linux does
some deep magic in ps(1)?); moving the PL_origalen computation
earlier makes also the threaded-first case fully pass.

But in general modifying the argv[] is very non-portable.
(e.g. in Tru64 it seems to be limited to the size of the
original argv[0] since the argv[] are not contiguous?)

Everybody should just have setproctitle().

p4raw-id: //depot/perl@19884

1 files changed, 8 insertions, 7 deletions

diff --git a/pod/perlvar.pod b/pod/perlvar.pod
index ad791dd71b..7667f1d75d 100644
--- a/pod/perlvar.pod
+++ b/pod/perlvar.pod
@@ -838,16 +838,17 @@ and C<$)> can be swapped only on machines supporting setregid().
 
 =item $0
 
-Contains the name of the program being executed.  On some operating
-systems assigning to C<$0> modifies the argument area that the B<ps>
-program sees.  This is more useful as a way of indicating the current
-program state than it is for hiding the program you're running.
-(Mnemonic: same as B<sh> and B<ksh>.)
+Contains the name of the program being executed.  On some (read: not
+all) operating systems assigning to C<$0> modifies the argument area
+that the B<ps> program sees.  Also note that depending on the platform,
+the maximum length of C<$0> may be limited to the space occupied by
+the original C<$0>.  This is more useful as a way of indicating the
+current program state than it is for hiding the program you're
+running.  (Mnemonic: same as B<sh> and B<ksh>.)
 
 Note for BSD users: setting C<$0> does not completely remove "perl"
 from the ps(1) output.  For example, setting C<$0> to C<"foobar"> will
-result in C<"perl: foobar (perl)">.  This is an operating system
-feature.
+result in C<"perl: foobar (perl)">.  This is an operating system feature.
 
 In multithreaded scripts Perl coordinates the threads so that any
 thread may modify its copy of the C<$0> and the change becomes visible