Код
NAME
fread, fwrite - binary stream input/output
SYNOPSIS
#include <stdio.h>
size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
size_t fwrite(const void *ptr, size_t size, size_t nmemb,
FILE *stream);
DESCRIPTION
The function fread() reads nmemb elements of data, each size bytes
long, from the stream pointed to by stream, storing them at the loca‐
tion given by ptr.
The function fwrite() writes nmemb elements of data, each size bytes
long, to the stream pointed to by stream, obtaining them from the loca‐
tion given by ptr.
For nonlocking counterparts, see unlocked_stdio(3).
RETURN VALUE
fread() and fwrite() return the number of items successfully read or
written (i.e., not the number of characters). If an error occurs, or
the end-of-file is reached, the return value is a short item count (or
zero).
fread() does not distinguish between end-of-file and error, and callers
must use feof(3) and ferror(3) to determine which occurred. 