exit 正常终止  abort 异常终止
Before termination, exit() performs the following functions in the order listed:
1. Call the functions registered with the atexit function, in the reverse order of their registration.
2. Flush all open output streams.
3. Close all open streams.
4. Unlink all files created with the tmpfile function.
           
The abort() function causes abnormal program termination to occur, unless the signal SIGABRT is being caught and the signal handler does not return.
Any open streams are flushed and closed.

abort 不会调用 atexit 注册的函数



#include "stdio.h"
#include "stdlib.h"

void func1(){
  printf("func1 before exit \n");
}

void func2(){
  printf("func2 before exit \n");
}

int main(){
  int input;
  scanf("%d", &input);

  atexit(func1);
  atexit(func2);
  
  printf("input=%d\n",input);

  switch(input){
  case 0:
    printf("正常退出\n");
    exit(EXIT_SUCCESS);
    break;
  case 1:
    printf("异常终止\n");
    abort();
    break;
  case 2:
  {
    char *path = getenv("PATH");
    printf("PATH=%s\n", path);
    break;
  }
  case 3:
    system("pwd");
    break;
  case 4:
    printf("exit with return code 4\n");
    exit(4);
    break;
  default:
    break;
  }
  printf("done\n");
  
  return 0;
}