error: implicit declaration of function ‘sendfile’ is invalid in C99 [-Werror,-Wimplicit-function-declaration] code example
Example: error: implicit declaration of function 'write' is invalid in C99[-Werror,-Wimplicit-function-declaration]write(1, &c, 1);
implicit declaration of function 'read'
implicit declaration of function 'write'
//include this directive to make it work
#include <unistd.h>