[RndTbl] Ksh scripting, named pipes

[Kevin McGregor]

Aw. I was afraid of that. In my 'production' script there would be a long
time between most reads, so it's unlikely there would be a problem, but I
still don't want rare random failures. I'll find a work-around.


On Sat, Mar 1, 2014 at 2:12 PM, Adam Thompson <athompso at athompso.net> wrote:

> Oh, it's obvious when I think about it - the behavior of a pipe with
> multiple readers is well-defined as being OS and clib-dependent.
> Each byte is only available to one reader, ever - if the reading is
> interleaved, each reader will get garbage.
> You can use tee(1) to write to multiple FIFOs at once, or just adapt the
> writing script to do so manually.
> -Adam
>
> On Mar 1, 2014 1:35 PM, Kevin McGregor <kevin.a.mcgregor at gmail.com> wrote:
> >
> > The writer is:
> > #/bin/ksh
> > PIPE=/tmp/backup.pipe
> > [[ ! -a $PIPE ]] && mkfifo $PIPE
> > # Start gzip processes
> > /opt/cronjobs/zip1 &
> > /opt/cronjobs/zip2 &
> >
> > # Process files needing compression
> > let 'fc=0'
> > ls /zonebackup/*tar | while read F; do
> >         echo $F >$PIPE
> >         let 'fc=fc+1'
> > done
> >
> > echo "end of list" >$PIPE
> > echo "end of list" >$PIPE
> > exit 0
> >
> > The readers are:
> > #/bin/ksh
> > PIPE=/tmp/backup.pipe
> > NAME=zip1
> > if [[ ! -a $PIPE ]]; then
> >         logger -p local0.warning "$NAME can't find $PIPE -- exiting"
> >         exit 1
> > fi
> >
> > while (( 1 )); do
> >         read F <$PIPE
> >         if [[ "$F" = "end of list" ]]; then
> >                 break
> >         else
> >                 echo "$NAME: $F"
> >         fi
> > done
> >
> >
> >
> > On Sat, Mar 1, 2014 at 1:29 PM, Kevin McGregor <
> kevin.a.mcgregor at gmail.com> wrote:
> >>
> >> I tried fiddling with IFS to no avail. I just changed it like this:
> >> IFS='
> >> '
> >> And now the readers show all kinds of gibberish! All lines have no
> whitespace, save for the newline at the end. I'm assuming it's at the end.
> >>
> >>
> >> On Sat, Mar 1, 2014 at 12:47 PM, Robert Keizer <robert at keizer.ca>
> wrote:
> >>>
> >>> Have you tried setting IFS ( field sep )? Also you could enable raw
> mode with -r.
> >>>
> >>> Can you share the script?
> >>>
> >>> Are the same lines failing repeatedly?
> >>>
> >>> Rob
> >>>
> >>> On 2014-03-01 11:55 AM, "Kevin McGregor" <kevin.a.mcgregor at gmail.com>
> wrote:
> >>>>
> >>>> I have a main script which writes to a named pipe. Before it starts
> writing, it starts two other scripts which read from this pipe. The reading
> and writing is a list of file names, one per line. How do I ensure that
> each script reads one complete line from the pipe at a time (no more, no
> less)?
> >>>>
> >>>> I have a test set up, and it usually works, but sometimes a reader
> will get a blank line or just a "/" (but not any other part of a line)!
> >>>>
> >>>> Kevin
> >>>>
> >>>> _______________________________________________
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> >>>>
> >>>
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> >>>
> >>
> >
>
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