Control stript which is runing in background.

[jak]

Il 02/01/2021 01:07, Alan Bawden ha scritto:
> jak <nospam at please.ty> writes:
> 
>     Il 01/01/2021 06:23, Alan Bawden ha scritto:
>     > jak <nospam at please.ty> writes:
>     >
>     >     Running the command:
>     >
>     >     $ cat bible.txt > cmdpipe & cat bible.txt > cmdpipe & cat bible.txt > cmdpipe
>     >
>     >     the three texts do not mix....
>     >
>     > The three texts do not mix as long at the contents of bible.txt is short
>     > enough (and provided `cat' only calls `write' once).  In the POSIX
>     > specification, the manual page for the `write' system call describes
>     > writing to a pipe or FIFO as follows:
>     >
>     >    Write requests of {PIPE_BUF} bytes or less shall not be interleaved
>     >    with data from other processes doing writes on the same pipe.  Writes
>     >    of greater than {PIPE_BUF} bytes may have data interleaved, on
>     >    arbitrary boundaries, with writes by other processes, whether or not
>     >    the O_NONBLOCK flag of the file status flags is set.
>     >
>     Ok. And...
>          ...Running the command:
> 
>          $ cat bible.txt > cmdpipe & cat bible.txt > cmdpipe & cat bible.txt > cmdpipe
> 
>          the three texts do not mix....
> 
> Saying it again doesn't make it any more true.  If bible.txt is large
> enough, they most definitely DO mix!  Just to make sure I wasn't missing
> something, I tested your exact command before I sent my previous reply.
> They mixed.
> 

This is really strange. On which system did you test? unix, linux or a
surrogate (cygwin, msys)? I asked this because bible.txt is 4.25MB size
(https://github.com/mxw/grmr/blob/master/src/finaltests/bible.txt)...
and the OP needs to send only commands (I hope smaller than the bible).