[英]How to set child's process std (out / err) as the parent in Linux
[英]Process id of the parent's parent - Linux
我有一個鏈中的三個過程:P1-> P2-> P3。 我希望能夠從child(P3)進程中打印出所有三個的ID。
因此,我的問題是如何使用getppid()等獲取子級孩子(P3)的父級父親(P1)的pid?
還是我不得不求助於將每個變量的pid存儲在自己的變量中供以后使用(不需要)?
謝謝您能給我的任何幫助。 另外,正因為如此,到目前為止,這是我的代碼:
//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,我最終使用堆棧來存儲信息。 如上面的代碼所示。
在子case 0:
時,您需要打印pid和ppid case 0:
請參考此代碼。
//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 );
}
你也可以從/ proc獲取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 0 17 0 0 0 221 0 0
上面(第4字段)中的20137是PPID。
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