父进程的进程id - Linux

Question

我在一个链中有三个进程: P1 -> P2 -> P3。我希望能够从子进程(P3)中打印出这三个进程的id。

那么，我的问题是如何使用getppid()之类的方法获得孙子(P3)的祖父母(P1)的pid？

或者我必须将每一个的pid存储在它们自己的变量中，以供以后使用(不可取)？

谢谢你能给我的任何帮助。另外，只是因为，这是我目前为止的代码：

//test_wait.cpp
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <stack>

using namespace std;

int main()
{
  pid_t pid;            //process id
  const char *message;
  int n;
  int exit_code;
  std::stack<int> proc_stack;

  cout << "Fork program starting\n";
  proc_stack.push(getpid());
  pid = fork();
  switch ( pid ) {
  case -1:
    cout << "Fork failure!\n";
    return 1;
  case 0:
    pid = fork();
    switch ( pid ) {
    case -1:
      cout << "Fork Failure!\n";
      return 1;
    case 0:
      cout << "Grandchild PID: " << getpid() << endl;
      cout << "Parent PID: " << getppid() << endl;
      cout << "Grand Parent PID: " << proc_stack.top() << endl;
      exit_code = 9;
      break;
    default:
      exit_code = 0;
      break;
    }
  default:
    exit_code = 0;
    break;
  }

//waiting for child to finish
  if ( pid != 0 ) {             //parent
    int stat_val;
    pid_t child_pid;

    child_pid = wait ( &stat_val );     //wait for child
  }
  exit ( exit_code );
}

因此，我最终使用堆栈来存储信息。如上面的代码所示。

Answer 1

在子case 0:中，您需要打印pid和ppid，请参阅此代码。

  //test_wait.cpp
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>

using namespace std;

int main()
{
  pid_t pid;            //process id
  const char *message;
  int n;
  int exit_code;

  cout << "fork program starting\n";
  pid = fork();
  switch ( pid ) {
  case -1:
    cout << "Fork failure!\n";
    return 1;
  case 0:
   cout << "Child1 finished: PID = " << getpid() << endl;
    cout << "Parent PID = " << getppid() << endl;
   pid = fork();
    switch ( pid ) {
    case -1:
      cout << "Fork Failure!\n";
      return 1;
    case 0:
    cout << "Child2 finished: PID = " << getpid() << endl;
    cout << "Parent PID = " << getppid() << endl;
      message = "This is the child\n";
      n = 5;
      exit_code = 9;
      break;
    default:
      message = "This is the parent\n";
      n = 3;
      exit_code = 0;
      break;
    }
  default:
    message = "This is the grand parent\n";
    n = 3;
    exit_code = 0;
    break;
  }
  for ( int i = 0; i < n; ++i ) {
    cout << message;
    sleep ( 1 );
  }
//waiting for child to finish
  if ( pid != 0 ) {             //parent
    int stat_val;
    pid_t child_pid;

    child_pid = wait ( &stat_val );     //wait for child
  }
  exit ( exit_code );
}

你也可以从/proc获取ppid。

cat /proc/ PID /stat，例如PID #20467：

cat /proc/20467/stat

20467 (abc) S 20137 20467 20125 34818 20467 4202496 1930 5196 22 0 113 162 32 25 20 0 1 0 1701252 14548992 1606 4294967295 4194304 6492552 2076847264 2076842300 694388884 0 0 0 134889479 2151083916 0 17 0 0 0 221 0 0 0

上面的第20137个(第4个字段)是PPID。