Set trigger on a single character

[Starko]

Hello,
I have an item which returns three different characters: z / g / n
z is fine.
n & g are wrong

So I wanted to write something like:
{server.domain.local:vfs.file.contents["C:\Folder\Item.txt"].last(0)}#z

So the Trigger goes PROBLEM everytime the letter in the text file is not z.
The textfile gets generated every 60 seconds.

But I think my expression only works for numbers. What do to with a single letter?

Thank you!

[steveboyson]

Why not just test for the "OK" string?

{server.domain.local:my_item.str("z")#1}

means: trigger fires if string "z" is not found.

[Starko]

It worked, but I had to write it a little bit different:

{server.domain.local:vfs.file.contents["C:\Folder\Item.txt"].str(z)}#1

Thank you very much!