pvput requires value field or else it fails

[mrkraimer]

The following does not work

mrk> pvput -r timeStamp.userTag PVRdouble 50
Old : 
structure 
    structure timeStamp
        int userTag 0


Error: Structure has no .value
New : 
structure 
    structure timeStamp
        int userTag 0

The following does work

mrk> pwd
/home/epicsv4/masterCPP/exampleCPP/exampleClient
mrk> bin/linux-x86_64/put -r "timeStamp.userTag" PVRdouble
provider pva channelName PVRdouble request timeStamp.userTag debug false
_____put starting__
enter one of: exit put get
channelPutConnect PVRdouble status Status [type=OK]
put
enter value or values to put
50
exit
mrk> pvget -r "timeStamp.userTag" PVRdouble
PVRdouble
structure 
    structure timeStamp
        int userTag 50

[mdavidsaver]

mrk> pvput -r timeStamp.userTag PVRdouble 50

Try:

pvput -r timeStamp.userTag PVRdouble timeStamp.userTag=50

I found the previous (argument stack) behavior of pvput to be extremely non-intuitive. eg. It requires that a user anticipate whether a PV is a scalar or or an array. An incorrect assumption can fail in unexpected ways. Of course it also depends on specific handling of pvRequest which I don't like.

The new behavior requires the user to be explicit in what is intended by naming <field>=<value> with the exception of a shorthand notation which only applies to .value (which I see as the 90% case).

The updated help lays this out as:

$ pvput -h
Usage: pvput [options] <PV name> <value>
       pvput [options] <PV name> <size/ignored> <value> [<value> ...]
       pvput [options] <PV name> <field>=<value> ...
       pvput [options] <PV name> <json_array>
       pvput [options] <PV name> <json_map>
...
Examples:

  pvput double01 1.234       # shorthand
  pvput double01 value=1.234

  pvput arr:pv X 1.0 2.0  # shorthand  (X is arbitrary and ignored)
  pvput arr:pv "[1.0, 2.0]"            # shorthand
  pvput arr:pv value="[1.0, 2.0]"

[mdavidsaver]

the exception of a shorthand notation which only applies to .value

The shorthand is intended to mimic caput.