linux-C子进程退出信号

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>

void signal_hander()
{//处理子进程退出信号
  int child_status;
  wait(&child_status);  
  printf("child exited.\n");
}
int main(int argc,char **argv)
{//进程
  pid_t pid;
  int child_status;
  signal(SIGCHLD,signal_hander);
  if ((pid=fork())==0){
     printf("child process run!\n");
     exit(0);
  }else{
     printf("parent process run!\n");
     sleep(10); 
  }
  exit(0); 
}

 deepfuture-lx@deepfuture-lx-desktop:/media/LX/deepfuture$ gcc -o test10 test10.ctest10.c: In function ‘main’:

test10.c:20: warning: incompatible implicit declaration of built-in function ‘exit’

test10.c:26: warning: incompatible implicit declaration of built-in function ‘exit’

deepfuture-lx@deepfuture-lx-desktop:/media/LX/deepfuture$ ./test1

0parent process run!

child process run!

child exited.