calculated items

[rsokoll]

Hi,

I want to know how many incoming bytes have crossed my router's eth0 within the last 30 days.
From my understanding, I need a calculated item that substracts the value of last(//net.if[eth0],30d) from last(//net.if[eth0]), but that raises a syntax error:

Incorrect value for field "Formula": invalid second parameter in function "last".

My formula is

last(//net.if[eth0]) - last(//net.if[eth0],30d)

What am I missing?

[Brambo]

I think you should have

sum(last(//net.if[eth0]) - last(//net.if[eth0],30d))

[cyber]

I think you should have

sum(last(//net.if[eth0]) - last(//net.if[eth0],30d))

That is pretty useless ... as it is wrong from the start...

you have to remember that "last" is kind of special needs kid.. you cannot use last(/host/item,1d) to refer to a value one day ago... last has only "#num (optional) - the Nth most recent value". no "seconds" option..
so if you want to refer to a value X time ago, you need to use time shift (last (/host/key,<#num<:time shift>>)) https://www.zabbix.com/documentation...ion#time-shift
I think "last(//net.if[eth0]) - last(//net.if[eth0],#1:now-30d)" should work...

[valerio.bozzolan]

> you cannot use last(/host/item,1d) to refer to a value one day ago

(Sorry for necroposting) Note that you mentioned the documentation of Zabbix 6.0, but that documentation also says that the `last()` function actually supports a "time shift parameter".

See the documented syntax:

```
last (/host/key,<#num<:time shift>>)
```

https://www.zabbix.com/documentation/6.0/en/manual/appendix/functions/history#last

https://www.zabbix.com/documentation/7.0/en/manual/appendix/functions/history#last

I'm unsure if this is a bug in the Zabbix documentation. I'm just pretty much sure that:

- "last(//something)" works
- "last(//something, #2)" works
- "last(//something, 2)" does not work. Error: Invalid parameter "/1/params": invalid second parameter in function "last".
- "last(//something, 2h)" does not work Error: Invalid parameter "/1/params": invalid second parameter in function "last".

[cyber]

valerio.bozzolan commented
Yesterday, 12:16
> you cannot use last(/host/item,1d) to refer to a value one day ago

(Sorry for necroposting) Note that you mentioned the documentation of Zabbix 6.0, but that documentation also says that the `last()` function actually supports a "time shift parameter".

See the documented syntax:

```
last (/host/key,<#num<:time shift>>)
```

Read again please..
I have never claimed that it does not support time shift.. It has to be correctly formatted. You cannot use it as "...,30d", you need to format it as "...,#1,now-30d", ie last value from the moment of 30 days ago. which by all means can actually be whatever amount of time before that, it is just a last value before that 30d gap... We go back in time for 30 days and then look for last value from that moment.

• I'm unsure if this is a bug in the Zabbix documentation. I'm just pretty much sure that:
  • - "last(//something)" works
    - "last(//something, #2)" works
    - "last(//something, 2)" does not work. Error: Invalid parameter "/1/params": invalid second parameter in function "last".
    - "last(//something, 2h)" does not work Error: Invalid parameter "/1/params": invalid second parameter in function "last".

There is absolutely no bug here... omitting #X from parameters defaults to #1, ie last value. ",#2" refers to secoind to last value. ",2" and ",2h" do not work as last() has no "seconds" option.