How to select only a part of the input

[louisgi]

Hello,

I am working on a dashboard and I would like to keep only the first letter of the input (text) so that I can use it to call the correct datamodel in the query (my datamodels are untitled "A" "B" "C" in order to classify names).

If you have an idea, feel free to post it. 

Thanks in advance

[richgalloway]

Here's one way:

... | eval letter=substr($inputToken$, 0, 1)