Scripts

There are various places inside the configuration (other than the script module) that allow script input to dynamically set values.

Scripts are passed to sh -c.

Two types of scripts exist: polling and watching:

• Polling scripts will run and wait for exit. Normally they will repeat this at an interval, hence the name, although in some cases they may only run on a user event. If the script exited code 0, the stdout will be used. Otherwise, stderr will be printed to the log.
• Watching scripts start a long-running process. Every time the process writes to stdout, the last line is captured and used.

One should prefer to use watch-mode where possible, as it removes the overhead of regularly spawning processes. That said, there are some cases which only support polling. These are indicated by Script [polling] as the option type.

Writing script configs

There are two available config formats for scripts, shorthand as a string, or longhand as an object. Shorthand can be used in all cases, but there are some cases (such as embedding scripts inside strings) where longhand cannot be used.

In both formats, mode is one of poll or watch and interval is the number of milliseconds to wait between spawning the script.

Both mode and interval are optional and can be excluded to fall back to their defaults of poll and 5000 respectively.

Shorthand (string)

Shorthand scripts should be written in the format:

mode:interval:script

For example:

poll:5000:uptime -p | cut -d ' ' -f2-

Longhand (object)

An object consisting of the cmd key and optionally the mode and/or interval keys.

JSON

{
  "mode": "poll",
  "interval": 5000,
  "cmd": "uptime -p | cut -d ' ' -f2-"
}

YAML

mode: poll
interval: 5000
cmd: "uptime -p | cut -d ' ' -f2-"

YAML

mode = "poll"
interval = 5000
cmd = "uptime -p | cut -d ' ' -f2-"

Corn

{
  mode = "poll"
  interval = 5000
  cmd = "uptime -p | cut -d ' ' -f2-"
}