Offset must be a double error when reading file byte by byte

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Lev Mihailov 2022-2-15

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https://ww2.mathworks.cn/matlabcentral/answers/1650085-offset-must-be-a-double-error-when-reading-file-byte-by-byte

评论： Jan 2022-2-16

I read the file byte by byte, I know the byte structure, the small end is 220,400,600,1000 and then 1220,1620... bytes, all values are uint16, I need to get a matrix for each byte order, i.e. 220:N, 420:N (N is the length of the file)

fid=fopen(fileName,'rb') % opens the file for reading
x1 = fread(fid, Inf, 'uint8', 220);
fseek(fid, 'bof', 220);
x2 = fread(fid, Inf, 'uint8', 400);
fseek(fid, 'bof', 620);
x3 = fread(fid, Inf, 'uint8', 600);
fseek(fid, 'bof', 1020);
x4 = fread(fid, Inf, 'uint8', 1000);
fclose(fid);
Error using fseek
Offset must be a double.
Error in Untitled3 (line 27)
fseek(fid, 'bof', 220);

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Jan 2022-2-15

在 MATLAB Online 中打开

By the way, specifying the 'b' format in FOPEN is outdated for over 20 years.

The problem looks strange. If the opening of the file fails, another message is shown. Are you using the standard function fseek() of Matlab? What is the output of:

which fseek -all

Lev Mihailov 2022-2-15

Yes, I use the standard function, the code is presented, it’s just a task to read the file byte by byte, the structure is very convenient, but for some reason it’s impossible to read 400, 600 and 1000 bytes of information

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