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From: mike@george.uh.edu (Mike Frederick)
Newsgroups: comp.sys.mac.programmer,comp.sys.mac
Subject: Finding the current position of an open file--again
Message-ID: <5753.25f634f1@george.uh.edu>
Date: 8 Mar 90 16:33:21 GMT
References: <5743.25f51321@george.uh.edu>
Organization: University of Houston
Lines: 18

In article <5743.25f51321@george.uh.edu>, mike@george.uh.edu (Mike Frederick) writes:
> If I know the ioRefNum of an open file, how do I find the current file
> position?  In other words, how can I know where the read will be in an open
> file?
> 
> Mike Frederick
> MIKE@UH.EDU

The answers (thanks!) that I have received so far reminded me why I almost
never post questions; I can't seem to get the context completely right.
Therefore, let me try again:

I am attempting to learn exactly how a program (for which I do not have source)
works.  I have trapped a READ (xA002), and I can see the paramBlock with the
ioRefNum in it.  Using only MacBugs, how can I get to the file mark?  I see
something called a File Control Block which is kept in memory for each open
file, and it a field called fcbCrPs which is described as "mark".  Is this
what I want, and how do I get to the correct FCB from the paramBlock?