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Binary file reading.

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Pappu Murthy
Pappu Murthy on 11 Sep 2018
Commented: Greg on 14 Sep 2018
I have a binary file data which I am trying to read. the first data of record is 8 integer numbers. They are precision "int" which means each number is 4 byte long. so I use A = fread(fid,[1 8],'int') it showas numbers A(2) thru A(8) correctly... but number A(1) is some strange number. Also the last number is missing. If I do A = fread(fid, [1,9],'int') and take the numbers A(2) thru A(9) I am able to read all my numbers correctly. SO my question is why the very first number is some unwanted stuff and needs to be skipped to read correctly.

Accepted Answer

Greg
Greg on 11 Sep 2018
Edited: Greg on 11 Sep 2018
Nobody can possibly answer your question: "why... unwanted stuff...?" Only the author of the binary file format can tell you that. --More specifically, those 4 bytes actually exist in the file. MATLAB isn't misbehaving in any way.
I can tell you that you've already solved your problem. Simply skip 4 bytes and proceed. I bet they are useful somehow, but not likely as an int32. Try other 4-byte formats like float32, or 4*char. Maybe it's a float32 datestamp?
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Greg
Greg on 14 Sep 2018
FYI, frewind is redundant immediately after fopen.
Further, fseek is better than reading and trashing unwanted bytes. For a single value it won't make much difference in speed, but the code is cleaner.
*Accidentally posted as answer. Moved to comment *

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