Your question is related to phonology.

Usually all words have a stressed syllable, those who don't have such feature are usually monosyllables (they are typically function words or grammatical words/particles), and so they have a weak form and a strong form.

Those words are (I'll paste it from Wikipedia because I don't remember them all):


  a, am, an, and, are, as, at, be, been, but, can, could, do, does, for, from, had, has, have, he, her, him, his, just, me, must, of, shall, she, should, some, than, that, the, them, there, to, us, was, we, were, who, would, you


As you can see, "but" is on the list. The pronunciations you listed for it, [bʌt] and [bət], are respectively the strong form and the weak form.

Now, I don't remember exactly all the cases (I should look back in my notes because I did this at university), but usually the weak form is used in normal speech, unless you emphasize it then you use the strong form. Another distinction is between "particle used at the end of the sentence" vs. "particle used before a noun", for example:

I found what I'm looking for. --> [fɔː(r)]
I'm looking for money. ---------> [fə(r)]

Look here if you want to hear the pronunciation. (Check the BrE one, it gives the idea better.)

How do you pronounce "but"?
I am using Maven Assembly plugin to bundle my application along with configuration/settings files. It allows to specify persmissions to be stored along with files, which is quite convenient.

Still I never found a confirmation, that ZIP archive is capable of storing UNIX permissions. Is it? (please, post some proof if you answer either yes or no).
