fread（＆c，1，1，input）和fgetc（input）之间的区别，用于读取一个字节

Question

I'm currently trying to read in a PNG file, one byte at a time, and I'm getting different results when I use fread((void*), size_t, size_t, FILE*) and fgetc(FILE*) .

I essentially want to "Read one byte at a time until the file ends", and I do so in two different ways. In both cases, I open the image I want in binary mode through:

FILE* input = fopen( /* Name of File */, 'rb');

And store each byte in a character, char c

fread: while( fread(&c, 1, 1, input) != 0) //read until there are no more bytes read

fgetc: while( (c = fgetc(input)) != EOF) //Read while EOF hasn't been reached

In the fread case, I read all the bytes I need to do. The reading function stops at the end of the file, and I end up printing all 380,000 bytes (which makes sense, as the input file is a 380kB file).

However, in the fgetc case, I stop once I reach a byte with a value of ff (which is -1, the value of the macro EOF .

My question is, if both functions are doing the same thing, reading one byte at a time, how does fread know to continue reading even if it comes across a byte with a value of EOF ? And building off of this, how does fread know when to stop if EOF is passed when reading the file?

Answer 1

fgetc returns an int , not a char . EOF (and many actual character codes) cannot be stored in a char and attempting to do so will result in Undefined Behaviour. So don't do that. Store the return value in an int .