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Using Go text/template for Advanced Data Filtering

This document demonstrates the usage of the Go text/template package to filter and format the output of the ovp8xx get command for manipulating the result data. There are two custom functions created to enhance the filtering: prefix and toJSON.

The prefix Function

The prefix function is designed to solve the problem of trailing commas, which are, for example, not allowed in JSON. The idea is to prefix each line with a comma, except for the very first one. This function is particularly useful when generating JSON output dynamically, where the number of elements may vary.

Here's how it's used in the command:

ovp8xx get  --format '{ "ports": { {{$p := prefix ", "}}{{- range $key, $val := .ports -}}{{call $p}}"{{- $key -}}":{"state": "{{ .state }}"}{{- end }} } }'

In this command, {{$p := prefix ", "}} initializes the prefix function with a comma and a space. Then, {{call $p}} is used to insert the prefix before each port entry. The prefix function ensures that no comma is inserted before the first entry.

The result is a JSON object where each line, except the first, is prefixed with a comma:

{
  "ports": {
    "port0": {
      "state": "RUN"
    },
    "port1": {
      "state": "RUN"
    },
    "port2": {
      "state": "RUN"
    },
    "port3": {
      "state": "RUN"
    },
    "port6": {
      "state": "RUN"
    }
  }
}

Print all ports with some details

The following command retrieves all port data and formats it for easy reading:

ovp8xx get  --format '{{$p := prefix "\n"}}{{ range $port, $details := .ports }}{{call $p}}[{{ $port }}] state: {{ $details.state }},{{print "\t"}}type: {{ $details.info.features.type }},{{print "\t"}}PCIC Port: {{ $details.data.pcicTCPPort }}{{ end }}'

The result will look like:

[port0] state: RUN,     type: 3D,       PCIC Port: 50010
[port1] state: RUN,     type: 3D,       PCIC Port: 50011
[port2] state: RUN,     type: 2D,       PCIC Port: 50012
[port3] state: RUN,     type: 2D,       PCIC Port: 50013
[port6] state: RUN,     type: IMU,      PCIC Port: 50016

Modify the state of the ports

Now we are taking the example from the prefix function and enhance it to also modify the state of all ports (except port6) to CONF with the following command:

ovp8xx get  --format '{{ $state := "CONF" }}{ "ports": { {{$p := prefix ", "}}{{- range $key, $val := .ports -}}{{ if ne $key "port6" }}{{call $p}}"{{- $key -}}":{"state": "{{ $state }}"}{{end}}{{- end }} } }'

The output will be a JSON object that can be directly piped into the set command:

{
    "ports": {
        "port0": {
            "state": "CONF"
        },
        "port1": {
            "state": "CONF"
        },
        "port2": {
            "state": "CONF"
        },
        "port3": {
            "state": "CONF"
        }
    }
}

To directly apply those changes to the device, use the following command:

ovp8xx get  --format '{{ $state := "CONF" }}{ "ports": { {{$p := prefix ", "}}{{- range $key, $val := .ports -}}{{ if ne $key "port6" }}{{call $p}}"{{- $key -}}":{"state": "{{ $state }}"}{{end}}{{- end }} } }'  | ovp8xx set