Experimental Physics and
Industrial Control System

Ben Franksen via Tech-talk <tech-talk at aps.anl.gov> · Fri, 16 Apr 2021 10:37:58 +0200

Am 15.04.21 um 18:46 schrieb Johnson, Andrew N. via Tech-talk:
> On Apr 15, 2021, at 11:26 AM, Manoussakis, Adamandios 
> <manoussakis1 at llnl.gov> wrote:
>> I was looking mostly into the epics.camonitor or the auto_monitor 
>> parameter (seems like camonitor just when you create the pv you
>> can set this?) in pyepics.  The python script is just a small file 
>> generator that does some basic calculations.  I was trying to have 
>> CSS just call it to run to avoid having another application to
>> deal with.  Either by pressing a button (execute command works fine
>> but cannot get the execute to trigger based off a rule that I know
>> of) or by a pv changing value and css calling the script (jython 
>> doesn’t work with numpy/pandas).
> 
> You might want to take a look at the separate Kryten program 
> available from https://github.com/andrewstarritt/kryten which can 
> monitor PVs and run specified commands or scripts on conditions 
> related to those PVs. Since this wouldn’t be running inside your GUI 
> it isn’t subject to the problems related to running multiple 
> instances which Michael mentioned.
I recently had a case where I needed that functionality for a simple
test script. I resorted to plain shell scripting, see below. As written
the code works only for a single PV but I guess it wouldn't be hard to
add some filtering / case distinctions in the loop body in case you need
to monitor more PVs.

```
sel=0
caput BPMMUXCB:sel $sel
camonitor -t n BPMMUXCB:st | while read line; do
  st=$(echo -n "$line"|cut -b 33-)
  echo "st=$st"
  if test $sel = $st; then
    sel=$(( ($st + 1) % 32 ))
    caput BPMMUXCB:sel $sel >/dev/null
    echo "sel=$sel"
  fi
done
```

Ben
-- 
I would rather have questions that cannot be answered, than answers that
cannot be questioned.  -- Richard Feynman

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System