2.c

#include <stdio.h>
#include <string.h>

#include <unistd.h>

int r_write(int fd, char *buf, int len)
{
    int ret, w = 0;

    while (len != 0)
    {
        ret = write(fd, buf, len);
        if (ret == -1 && errno == EINTR)
        {
            continue;
        }
        if (ret == -1)
        {
            break;
        }

        w += ret;
        len -= ret;
        buf += ret;
    }

    return w;
}

int main(void)
{
    char str[] = "hello world\n";
    int ret;
    char buf[1024];

    ret = r_write(1, str, sizeof(str));
// printf("ret = %d\n", ret);


    snprintf(buf, 1024, "ret = %d\n", ret);
    write(1, buf, strlen(buf));

    write(1, "", 1);

    return 0;
}