Regex syntax to check prefixes and suffixes

Question

I'm building some regex expressions to match naming conventions in Sigasi Studio (which uses Java syntax for regex). For example, a port name must end in _i or _o - e.g. my_input_port_i

I tried using the txt2re generator, however instead of a simple expression it generated code.

Looking at regex syntax, it seems that the "$" character (end of line) and the "|" symbol (OR) could be helpful - something like $_i|_o but after testing with regex101.com no matches are found.

Naming convention dialog:

Answer 1

In Sigasi Studio the entire name should match. So your are looking for:

.*_[io]

Answer 2

The $ means end of the string, but you use it at the beginning.

Maybe you are looking for this at the end of the string, which uses an underscore _, then a character class to match i or o and then matches the end of the string $

_[io]$