Can someone explain me the "diff/last" trigger please ?

[jusavard]

Hi,
My question might seem silly but I one of my collegue shows me that there seems to be a difference between the zabbix man of using the "siff trigger" and the actual way of using it.
In the man :

diff
Checking if last and previous values differ.		Supported value types: float, int, str, text, log Returns: 1 - last and previous values differ 0 - otherwise

However when we use it :

{Template OS Windows:agent.hostname.diff(0)}>0

I can explain the ">0" saying that the trigger compare the last and previous value of the Item and if it' something different than 0 the item is flaged as "PROBLEM" but I can't explain the "(0)" .

Why do we need to specify it ?
Shouldn't we use it as "{Template OS Windows:agent.hostname.diff}>0" ?
Is it because the function really need an inut value even if it's kinda dropped in this case ?

[tcilmo]

You don't need specify the "0" - the function can be : ".diff()}>0

[jusavard]

Does it means whatever the value I put there it will be ignored because the function does not really need one ?

[tcilmo]

The function is not designed to take a parameter - none are defined in the doc: https://www.zabbix.com/documentation...gers/functions

[jusavard]

Exactly ! According to the man the function is not designed to take a parameter, however, as of Zabbix 3.0.5, the trigger difined for the agent.version and agent.hostname in the "Template OS Windows", "Template OS Linux", "Template OS [Whatever]" does have one. Go see by yourself in your installation in Configuration/Template.
That's pretty wierd to see ZAbbix comes with default Template with default trigger using a function with "0" as input where this function does not need any. Anyway, I guess the "diff" function simply ignore the 0 sent as input.