I don't understand what this parameters in the system call accept4 means

Hi! Newbie question here. I got the following from strace:

Code:

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accept4(8<UNIX:[246]>, {sa_family=AF_UNIX}, [110->2], 0) = 9<UNIX:[2512219]>

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First argument is ok to me:
8 is the file descriptor of the existing UNIX socket 246.

Second argument is supposed to be a pointer to a struct sockaddr, instead we have that weird thing between brackets. I don't really understand that declaration of a pointer and I would like to understand what

Code:

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{sa_family=AF_UNIX}

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means exactly and where is it pointing at.

Third argument is also a mistery I have no clue what 110 is neither what the 2 means neither why 110 is pointing to 2 or how this is a pointer to the lenght of the socket.

Fourth arguent is ok too