MATLAB Programming

Using Low-Level File I/O Functions
fid is the file identifier for the file. offset is a positive or negative offset
value, specified in bytes. origin is one of the following strings that specify
the location in the file from which to calculate the position.
'bof'
'cof'
'eof'
Beginning of file
Current position in file
End of file
Understanding File Position
To see how fseek and ftell work, consider this short M-file:
A = 1:5;
fid = fopen('five.bin','w');
fwrite(fid, A,'short');
status = fclose(fid);
This code writes out the numbers 1 through 5 to a binary file named five.bin.
The call to fwrite specifies that each numerical element be stored as a short.
Consequently, each number uses two storage bytes.
Now reopen five.bin for reading:
fid = fopen('five.bin','r');
This call to fseek moves the file position indicator forward 6 bytes from the
beginning of the file:
status = fseek(fid,6,'bof');
This call to fread reads whatever is at file positions 7 and 8 and stores it
in variable four:
four = fread(fid,1,'short');
6-109