fprintf and fread, character beyond ascii in 1 byte

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MarsMat
MarsMat 2016-3-23
回答： Walter Roberson 2016-3-23
Hi everyone. I'd like to ask if there is a way to write characters beyond 127 with 1 byte? I got a file which was saved in such a way, But I can not write back in the same way. So to speak, if I use "fread" to read in the file byte by byte, at some of them it is a number larger than 127. As shown in the code, if I write a character by 128, it became a 2 bytes (fread get back 2 numbers). How would I write it in order to get also 1 byte 128 back?
fid=fopen('test','w')
fprintf(char(128))
fclose(fid)
fid=fopen('test','r')
test=fread(fid)
fclose(fid)

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Walter Roberson
Walter Roberson 2016-3-23
Your test code forgot to mention fid in the fprintf() so it did not output anything.
Remember that when you use fprintf() with the syntax fprintf(fid, A_String) that the values in A_String are treated as being the format specifier and so are subject to interpretation. The exception to this is if you are sending to a serial device or instrument, in which ase fprintf(fid, A_String) is equivalent to fprintf(fid, '%s\n', A_String) . If you want the exact string sent, you should use fwrite(fid, A_String) instead of fprintf(fid, A_String)
Anyhow, what you might be running into is that fopen() with so few parameters opens the file with the default character encoding for your system. You should fopen() with 4 parameters:
fid=fopen('test','w', 'n', 'ISO-8859-1')
See http://www.mathworks.com/help/matlab/ref/fopen.html#inputarg_encodingIn
(Note: the third parameter, 'n' in this example, cannot be skipped or left at '' or [] if you need to provide the encoding.)

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