Re: Buffered I/O and ed shell escape command

[Antonio Diaz Diaz]

Hi Sören,

Sören Tempel wrote:
> I did some experiments with the shell escape command today and noticed
> that the command behavior depends on the output stream on my system:

Thank you very much for reporting this. I have fixed it by flushing stdout 
as in the patch below. I'll soon release a new version of ed.

--- main_loop.c~        2021-12-04 00:55:35.000000000 +0100
+++ main_loop.c         2021-12-29 16:31:03.000000000 +0100
@@ -154,7 +154,7 @@
   if( !resize_buffer( &shcmd, &shcmdsz, i + 1 ) ) return 0;
   memcpy( shcmd, buf, i );
   shcmd[i] = 0; shcmdlen = i;
-  if( replacement ) printf( "%s\n", shcmd + 1 );
+  if( replacement ) { printf( "%s\n", shcmd + 1 ); fflush( stdout ); }
   return shcmd;
   }


Alexander Jones wrote:
> I wouldn't put too much stock into comparing the GNU version of ed with
> OpenBSD's, since they both ultimately derive from the same implementation
> (written in the early-to-mid 1990s by Andrew Moore) and thus could share
> long-standing bugs. That being said, I concur with your reading of the
> POSIX spec that the modified command string should be printed before the
> command is executed, so this is likely a bug that should be fixed in GNU
> and reported to the various BSDs.

Agreed. In spite of the many changes made in GNU ed since 2006, most of the 
code still comes from Andrew's implementation of 1993-1994, so this bug may 
be also present in BSD ed.


Best regards,
Antonio.