unix-0103a

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
int fd;
int f1()
{
    static int j = 1;
    if (j > 10) return 0;
    write(fd, &j, sizeof(int));
    printf("write %d -- %d\n", fd, j++);
    return 1;
}

void f2()
{
    int i;
    lseek(fd, -sizeof(int), 1);
    read(fd, &i, sizeof(int));
    printf("read %d -- %d\n", fd, i);
}
int main(int argc, char *argv[])
{
    if (argc < 2)
        puts("Format: rw filename");
    else
        {
        fd = open(argv[1], O_CREAT | O_RDWR);
        while (f1())
            f2();
        close(fd);
    }
        return 0;
}