使用 fork() 在子进程中没有获得适当的父 ID

Question

I am trying to get the parent id in the child process using fork() . However, I don't get the proper parent id. Sometime I do and sometime I don't. My printf prints 1 for the parent id. Here is my code snippet. Can anyone explain the reason.

for(i = 1 ; i <= n ; i++){      
    if((pid = fork()) == 0){
        printf("Parent id is %u\n", getppid()) ;            
        break ;
    }
}  

Answer 1

The process with the id of 1 is the init process. Output from top -p 1 (on my Ubuntu machine):

PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND             
    1 root      20   0 24732 2704 1376 S    0  0.0   0:00.93 init

If a process is orphaned the init process adopts the orphaned process , and getppid() will return 1 in the orphaned process. In your case, the parent process must be exiting, on occasion, before the child process calls getppid() .