feof returns true if and only if the end of a STREAM file has been reached during a readline, readbytes, or fscanf operation. Otherwise, feof returns false.

The end of file must actually have been encountered. For example, asking readbytes to read 20 bytes when only 19 remain in the file will result in a subsequent feof call returning true. On the other hand, reading the last line of a file with readline does not encounter the end of file; a subsequent call to readline will.

if a file name is given, and that file is not yet open, it is opened in READ mode with type BINARY.