init.c

// init: The initial user-level program

#include "types.h"
#include "stat.h"
#include "user.h"
#include "fcntl.h"

char *argv[] = { "sh", 0 };

int
main (void)
{
    int pid, wpid;

    if (open ("console", O_RDWR) < 0)
    {
        mknod ("console", 1, 1);
        open ("console", O_RDWR);
    }
    dup (0);                    // stdout
    dup (0);                    // stderr

    for (;;)
    {
        printf (1, "init: starting sh\n");
        pid = fork ();
        if (pid < 0)
        {
            printf (1, "init: fork failed\n");
            exit ();
        }
        if (pid == 0)
        {
            exec ("sh", argv);
            printf (1, "init: exec sh failed\n");
            exit ();
        }
        while ((wpid = wait ()) >= 0 && wpid != pid)
            printf (1, "zombie!\n");
    }
}