Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 18 Apr 2014 10:25:02 -0500

Hi Mark,

On 04/18/2014 09:23 AM, Poff, Mark A wrote:
> Is it possible to pass a PV value as the argument of a program call from
> a MEDM Shell Command button?  It seems like that would be a useful
> capability, but I can’t find any reference to it.  Somebody posted this
> question in Tech-Talk for EDM in 2004 (“EDM: Passing PV values to shell
> commands”) but it doesn’t appear that the question was ever addressed. 
> Can anybody tell me whether this capability exists and if so, the syntax?

That's a great question. The answer is not directly, but you can have
the user select a PV from any widget on the display, and if you make the
shell command pass that through `caget -t` you can convert the name into
the PV's value before calling your program.

The Shell Command widget supports embedding the &P operator from the
Execute Menu command[1] which prompts the user to point to the PV to be
named before executing the command string.

Example: I create a Shell Command widget with a command set to
    echo `caget -t &P`
I also put at least one other PV on the screen. When I click the button,
the cursor changes to prompt me to click on a widget that will provide
the PV name. The caget command is then executed on that PV, and the
value returned gets echoed on the terminal where I started medm.

Of course if your PV name is fixed you don't have to use the &P part at
all, you can just name it directly in the caget call:
    echo `caget -t myPV`

Hope this helps,

- Andrew

[1]
http://www.aps.anl.gov/epics/EpicsDocumentation/ExtensionsManuals/MEDM/MEDM.html#ExecuteMenu

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System