ipc_ns_demo.c

#define _GNU_SOURCE
#include <sys/wait.h>
#include <sys/utsname.h>
#include <sched.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/sem.h>
#include <sys/ipc.h>
#include <sys/types.h>

#include <sys/types.h>
#include <sys/capability.h>


#define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \
                        } while (0)

#define COMMON_SEM_KEY 31338

static int              /* Start function for cloned child */
childFunc()
{
    printf("PID from child point of view just after clone() is %ld\n", (long) getpid());

    printf("example_sem_id in child is %ld\n",
           (long) semget(COMMON_SEM_KEY, 1, IPC_CREAT | IPC_EXCL));

    sleep(1);

    return 0;           /* Terminates child */
}

#define STACK_SIZE (1024 * 1024)    /* Stack size for cloned child */

static char child_stack[STACK_SIZE];

int
main(int argc, char *argv[])
{

    printf("example_sem_id in parent is %ld\n",
           (long) semget(COMMON_SEM_KEY, 1, IPC_CREAT|IPC_EXCL));

    pid_t child_pid;

    child_pid = clone(childFunc, 
                    child_stack + STACK_SIZE,   /* Points to start of 
                                                   downwardly growing stack */ 
                    CLONE_NEWIPC | SIGCHLD, NULL);
    printf("PID of child created by clone() is %ld\n", (long) child_pid);

    if (waitpid(child_pid, NULL, 0) == -1)      /* Wait for child */
        errExit("child wait failed");

    exit(EXIT_SUCCESS);
}