I should be able to detect that cat is a builtin version of /bin/cat and
implicitly treat it as /bin/cat. I'll put this on my list.
On Mon, Aug 18, 2014 at 9:18 AM, Dr. Werner Fink <wer...@suse.de> wrote:
> On Wed, Aug 06, 2014 at 09:03:22PM -0400, David Korn wrote:
> > I have attached a different fix that doesn't have the problem the last
> one
> > does. However, if the last command in the pipeline is a shell built-in,
> it
> > could hang for large output.
> >
> > Let me know if this works for you.
>
> It hangs as `cat' is a shell built-in in normal case:
>
> /usr/src/packages/BUILD/ksh93> ./arch/linux.i386-64/src/cmd/ksh93/ksh
> /usr/src/packages/BUILD/ksh93> x=`cat ~/testfile.txt | cat -`
> Killed
>
> whereas this one
>
> /usr/src/packages/BUILD/ksh93> x=`cat ~/testfile.txt | /bin/cat -`
> /usr/src/packages/BUILD/ksh93>
>
> does work ... IMHO both should work. The test suite does survive with
> this patch.
>
> Werner
>
> >
> >
> >
> > On Fri, Jul 25, 2014 at 4:04 AM, Dr. Werner Fink <wer...@suse.de> wrote:
> >
> > > On Thu, Jul 24, 2014 at 11:35:01AM -0400, David Korn wrote:
> > > > I finally got a chance to look at this.
> > > >
> > > > The problem is that the standard is ambiguous about when a command
> > > > substitution ends.
> > > >
> > > > The bourne shell used a pipe for command substitution and command
> > > > substitution terminated when the pipe closed. Thus, if you had a
> command
> > > > the wrote on standard output, forked and exited and the child wrote
> on that
> > > > pipe, the output from both processes was part of the command
> substitution.
> > > >
> > > > ksh considered the command substitution done when the command
> completed and
> > > > used memory for files less that 64K(IOBSIZE) and this created a tmp
> file
> > > > if it was larger.
> > > >
> > > > I tried to restore the old bourne shell semantics for `` so that the
> > > > foreback test would work. However, this caused the example you have
> to
> > > > hang. Here is a change which should fix this by using pipes for all
> `` not
> > > > just large ones. Here is the one line patch:
> > > >
> > > > --- old/sh/subshell.c Wed Apr 2 09:57:00 2014
> > > > +++new/sh/subshell.c Thu Jul 24 11:19:43 2014
> > > > @@ -593,7 +574,7 @@
> > > > sp->tmpfd = -1;
> > > > sp->pipefd = -1;
> > > > /* use sftmp() file for standard output */
> > > > - if(!(iop =
> sftmp(comsub==1?PIPE_BUF:IOBSIZE)))
> > > > + if(!(iop = sftmp(comsub==1?0:IOBSIZE)))
> > > > {
> > > > sfswap(sp->saveout,sfstdout);
> > > >
> > > > errormsg(SH_DICT,ERROR_system(1),e_tmpcreate);
> > > >
> > > >
> > > > Let me know.
> > > >
>
> --
> "Having a smoking section in a restaurant is like having
> a peeing section in a swimming pool." -- Edward Burr
>
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