确保父进程在子进程之前终止

Question

If I use the following line in the child after a fork :

while( getppid() != 1 )

to ensure that the parent terminates before the child (as when the parent terminates, the parent of the child process becomes the init process) then what possible problems could I face, if any ?

Is this a good way to ensure that the child terminates after the parent ?

What other way is there ?

Answer 1

spin loops are never a good thing. Open a pipe before you fork. Have the child block on a read. When the parent terminates, the pipe will close and the child will proceed. (Make sure the child closes the write side of the pipe!)

For example: (WARNING: ALL ERROR CHECKING OMITTED)

int
main( void ) {
    int fd[ 2 ];
    pipe( fd );
    if( fork() ) {
        sleep( 2 );
        puts( "parent awakes" );
    } else {
        char k;
        close( fd[ 1 ]);
        read( fd[ 0 ], &k, 1 );
        puts( "child continues" );
    }
    return 0;
}

Also note that the child ought to close the read side of the pipe when it's done, but I've left that out of the sample code since it is not relevant to the problem of waiting for the parent to terminate.