when i have a text like this "hello_hello" and i double click to select it.. it will only select from underscore to underscore.. not the whole text.. is this a bug? i prefer to select the whole text.
i am on OSX.
It's not an OS issue, it is an app issue. And many people here use the Arduino IDE, which is, ... an app! It may well be that the OS-provided TextEdit control has its own idea of what a "word" is, but that doesn't mean it can't be worked around. Most programming editors are smart enough to know what a word/atom is in the language the programmer is editing in...
i also use textwrangler and there i can select the the whole word underscore and everything.