Luna/apps/src/init.c

#include <errno.h>
#include <luna.h>
#include <stdio.h>
#include <sys/wait.h>
#include <unistd.h>

void show_motd()
{
    FILE* fp = fopen("/etc/motd", "r");
    if (!fp)
    {
        if (errno != ENOENT) { perror("fopen"); }
        return;
    }

    char buf[4096];
    size_t nread = fread(buf, sizeof(buf) - 1, 1, fp);
    if (ferror(fp))
    {
        perror("fread");
        fclose(fp);
        return;
    }
    buf[nread] = 0;

    puts(buf);

    fclose(fp);

    putchar('\n');
}

int main()
{
    if (getpid() != 1)
    {
        fprintf(stderr, "init should be started as PID 1\n");
        return 1;
    }

    show_motd();

    msleep(200);

    pid_t child = fork();
    if (child < 0)
    {
        perror("fork");
        return 1;
    }
    if (child == 0)
    {
        execv("/bin/sh", NULL);
        perror("execv");
        return 1;
    }

    pid_t result;

    for (;;)
    {
        while ((result = wait(NULL)) == 0) // No child has exited yet
        {
            msleep(100);
        }
        if (result == child) { return 0; }
    }
}