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comp.lang.c FAQ list · Question 12.38

Q: How can I read a binary data file properly? I'm occasionally seeing 0x0a and 0x0d values getting garbled, and I seem to hit EOF prematurely if the data contains the value 0x1a.

A: When you're reading a binary data file, you should specify "rb" mode when calling fopen, to make sure that text file translations do not occur. Similarly, when writing binary data files, use "wb". (Under operating systems such as Unix which don't distinguish between text and binary files, "b" may not be required, but is harmless.)

Note that the text/binary distinction is made when you open the file: once a file is open, it doesn't matter which I/O calls you use on it. See also questions 12.37, 12.40, 12.42, and 20.5.

References: ISO Sec.
H&S Sec. 15.2.1 p. 348

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