Table of Contents
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.
Three types of scripts exist: polling, oneshot 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
stdoutwill be used. Otherwise,stderrwill be printed to the log. - Oneshot scripts are a variant of polling scripts. They wait for script to exit, and may do something with the output, but are only fired by user events instead of the interval. Generally options that accept oneshot scripts do not support the other types.
- 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.
For oneshot scripts, both the mode and interval are ignored.
Shorthand (string)
Shorthand scripts should be written in the format:
mode:interval:script
For example:
poll:5000:uptime -p | cut -d ' ' -f2-
Embedding
Some string config options support "embedding scripts". This allows you to mix static/dynamic content.
An example of this is the common tooltip option.
Scripts can be embedded in these cases using {{double braces}} and the shorthand syntax:
"Up: {{30000: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-"
}