sendfile
int sendfile(int, int, off_t, size_t, struct sf_hdtr *, off_t *, int);
cnt = sendfile(rem, f, &off, amt);
if (sendfile(ar_outfile.fd, fd, &off,
if (sendfile(sock, fd, &off, st.st_size) != st.st_size)
#define sendfile64 sendfile
extern ssize_t sendfile(int, int, off_t *, size_t);