— binary stream
*ptr, size_t size,
void *ptr, size_t
size, size_t nmemb,
reads nmemb objects, each size
bytes long, from the stream pointed to by stream,
storing them at the location given by ptr.
writes nmemb objects, each size
bytes long, to the stream pointed to by stream,
obtaining them from the location given by ptr.
fwrite() advance the file position indicator for the
stream by the number of bytes read or written. They return the number of
objects read or written. If size or
nmemb is 0,
fwrite() return 0 with no change made to the
stream. If the product of size
and nmemb results in integer overflow, 0 is returned
and errno is set to
EOVERFLOW. If an error occurs,
or the end-of-file is reached, the return value is a short object count (or
fread() does not distinguish
between end-of-file and error, and callers must use
ferror(3) to determine which occurred. The function
fwrite() returns a value less than
nmemb only if a write error has occurred.
fwrite() conform to ANSI
X3.159-1989 (“ANSI C89”).
fwrite() first appeared in
Version 7 AT&T UNIX.