spinfo

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Print a PV's type structure without fetching its value. The equivalent of EPICS Base pvinfo.

spinfo [OPTIONS] [PV]

Requires the client feature. Uses the CMD_GET_FIELD (0x11) protocol command, so the server answers with an introspection description and no data.

Flags beyond the shared set

Output

$ spinfo VAC:SETPOINT
VAC:SETPOINT:
struct epics:nt/NTScalar:1.0
value: double
alarm: structure
  severity: int
  status: int
  message: string
timeStamp: structure
  secondsPastEpoch: long
  nanoseconds: int
  userTag: int
display: structure
  limitLow: double
  limitHigh: double
  description: string
  units: string
  precision: int
  form: structure
    index: int
    choices: string[]
control: structure
  limitLow: double
  limitHigh: double
  minStep: double
valueAlarm: structure
  active: boolean
  lowAlarmLimit: double
  lowWarningLimit: double
  highWarningLimit: double
  highAlarmLimit: double

What it is good for

Confirming the normative type. The first line is the type ID. If a client library refuses a PV, this tells you whether the server is really sending epics:nt/NTScalar:1.0 or something else.

Seeing the alarm limits. The valueAlarm block above exists because the record was built with .alarm_limits(...). The limits are on the wire, and spinfo proves it. Whether the server also evaluates them depends on compute_alarms: when it is on (spserver --compute-alarms or .compute_alarms(true)), every write is compared against these same limits and drives the severity; it is off by default, and then the limits are only published. spinfo shows the limits either way, which is how you tell metadata from computed severity. See Alarms.

Working out what -F can ask for. The dotted paths in spget -F and spmonitor -F are exactly the paths in this tree.