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From: dunadan@blake.u.washington.edu (Steven Owen)
Newsgroups: comp.sys.apple2
Subject: Applesoft problem: finding the end of a text file
Summary: How to do this without ONERR GOTO...
Message-ID: <14442@milton.u.washington.edu>
Date: 15 Jan 91 12:11:40 GMT
Sender: news@milton.u.washington.edu
Organization: The Broken Blade
Lines: 25

Here's an age-old Applesoft BASIC problem that I've come across while
reworking some old code:

When reading information from a TXT file, I have yet to find a satisfactory
way to determine where the end of a file is.  The most common method, I
suppose, is to slip in an ONERR GOTO statement just before you start reading
data from the file, and reference the line number just after the read command,
which usually closes the file and changes the ONERR GOTO line number to its
original reference.

Another way is to find the file's length, and keep track of how many bytes
you've read from the file (along with each CR), and stop when the two are
equal.  This should work, except in cases where the final line of the program
isn't terminated by a RETURN character (this method would work if you're using
GETs to retrieve the data, but that would be much too slow).

To get the file's length, you can either read the file's directory entry in
its parent DIR file (messy, and if the directory is large, this can take a
while), or poke a GET_EOF MLI call into memory (faster, but still a little
messy, even when using Amperworks' neat &MLI command).

It would be nice to have a one or two-line solution, but I don't suppose that
I'm going to find something as simple as "IF <EOF> THEN ...", am I?

--Mike Owen, Bladesmith at large