#include <stdio.h>
#include <errno.h>

char buf[BUFSIZ];

int main(int argc, char ** argv)
{
    size_t n;
    FILE * f = fopen("/dev/full", "w");
    /* n = setvbuf(f, (char *) NULL, _IOLBF, 0); */
    n = setvbuf(f, (char *) buf, _IOLBF, BUFSIZ);
    printf("setvbuf %zd %d\n", n, errno);
    n = fwrite("hello", 1, 5, f);
    printf("fwrite %zd %d\n", n, errno);
    n = fwrite("\n", 1, 1, f);
    printf("fwrite %zd %d\n", n, errno);
    n = fwrite("a", 1, 1, f);
    printf("fwrite %zd %d\n", n, errno);
    return 0;
}