文件描述符和exec() close_on_exec

#include <fcntl.h>
#include <iostream>
#include <unistd.h>
using namespace std;

int main()
{
    int flags = fcntl(STDOUT_FILENO, F_GETFD);

    flags |= FD_CLOEXEC;

    fcntl(STDOUT_FILENO, F_SETFD, flags);
    if ( fork() == 0 )
    {
        execlp("ls", "ls", (char*)NULL);
    }

    cout << "input flags = ";
    cin >> flags;
    cout << flags << endl;
    return 0;
}