IPC使用多个管道和分支进程来运行Python程序

IPC using multiple pipes and forked processes to run Python programs

本文关键字：进程 运行 Python 程序 分支 管道 IPC      更新时间：2023-10-16

我的作业遇到了一个问题。我正在尝试执行3个并发进程(在C++中(，其中2个是Python程序，其中一个是C++程序。

我的C++程序(sample.cpp(：

#include <unistd.h>
#include <stdio.h>
#include <string.h>  
#include <string>
#include <stdlib.h>
#include <iostream>
#include <vector> 
#include <signal.h>
using namespace std;
int main()
{
while (true)
{
cout << "lol" << endl;
sleep(2);
}
return 0;
}

我的Python程序1(sample.py(：

import sys
while True:
line = sys.stdin.readline().strip()
print "Python says: " + str(line)

我的Python程序2(sample2.py(：

import sys
while True:
line = sys.stdin.readline().strip()
print "Python 2 says: " + str(line)

这是我的驱动程序C++程序，它分叉处理：

#include <unistd.h>
#include <stdio.h>
#include <string.h>  
#include <string>
#include <stdlib.h>
#include <iostream>
#include <vector> 
#include <signal.h>
using namespace std;
int main()
{
vector<pid_t> kids;
int fd[2];
if (pipe(fd) < 0)
{
cout << "Error"; 
return 1; 
}
int fd2[2];
if (pipe(fd2) < 0)
{
cout << "Error";
return 1;
}
pid_t pid;
pid = fork();
if (pid == 0)
{
dup2(fd[1], STDOUT_FILENO);
close(fd[1]);
close(fd[0]);
while (true)
{
execvp("./sample", NULL);
}
}
else
{
kids.push_back(pid);
pid = fork();
if (pid == 0)
{
dup2(fd[0], STDIN_FILENO);
close(fd[0]);
close(fd[1]);
dup2(fd2[1], STDOUT_FILENO);
close(fd2[1]);
close(fd2[0]);
char * python = "/usr/bin/python";
char * pythonProgram = "./sample.py"; 
char * pythonArgs[] = {python, pythonProgram, NULL, NULL};
execvp(python, pythonArgs);
}
else
{
kids.push_back(pid);
pid = fork();
if (pid == 0)
{
dup2(fd2[0], STDIN_FILENO); 
close(fd2[0]);
close(fd2[1]);
char * python = "/usr/bin/python";
char * pythonProgram = "./sample2.py"; 
char * pythonArgs[] = {python, pythonProgram, NULL, NULL};
execvp(python, pythonArgs);
}
else
{
kids.push_back(pid);
}
}
}
close(fd[0]);
close(fd[1]);
close(fd2[0]);
close(fd2[1]);
for (pid_t k : kids) 
{
int status;
//kill (k, SIGTERM);
waitpid(k, &status, 0);
}
}

当我运行这个程序时，我会看到"Python 2说：Python说：lol"。然而，我什么也没看到(完全空白(。。。它只是挂着。我做错了什么？我试着查找了很多东西，但没有找到。

while循环围绕的开始/除非您期望execvp失败，否则示例是毫无意义的。成功调用exec*将永远不会返回。对execvp的实际调用也是错误的：

execvp("./sample", NULL);

第二个参数应该是CCD_ 1。

您应该为execvp:s添加错误处理(类似于带有std::exit(1)的行(。否则，如果execvp失败，您将在程序的主流中运行子进程。

python程序需要在没有缓冲区的情况下运行，否则将需要很长时间才能显示消息。您还应该检查readline是否成功。

示例.py

import sys
while True:
line = sys.stdin.readline().strip()
if not line: break
print "Python says: " + str(line)

sample2.py

import sys
while True:
line = sys.stdin.readline().strip()
if not line: break
print "Python 2 says: " + str(line)

驱动程序.cpp

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <string>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
int main()
{
vector<pid_t> kids;
int fd[2];
if (pipe(fd)==-1)
{
clog << "Errorn";
return 1;
}
int fd2[2];
if (pipe(fd2)==-1)
{
clog << "Errorn";
return 1;
}
pid_t pid;
pid = fork();
if (pid == 0)
{
dup2(fd[1], STDOUT_FILENO);
close(fd[1]);
close(fd[0]);
char* const args[] = { NULL };
execvp("./sample", args);
std::clog << "sample failedn";
std::exit(1);
}
else
{
kids.push_back(pid);
pid = fork();
if (pid == 0)
{
dup2(fd[0], STDIN_FILENO);
close(fd[0]);
close(fd[1]);
dup2(fd2[1], STDOUT_FILENO);
close(fd2[1]);
close(fd2[0]);
char const* python = "/usr/bin/python";
char const* pythonProgram = "./sample.py";
char const* pythonArgs[] = {python, "-u", pythonProgram, NULL};
execvp(python, const_cast<char* const*>(pythonArgs));
std::clog << "sample.py failedn";
std::exit(1);
}
else
{
kids.push_back(pid);
pid = fork();
if (pid == 0)
{
dup2(fd2[0], STDIN_FILENO);
close(fd2[0]);
close(fd2[1]);
char const* python = "/usr/bin/python";
char const* pythonProgram = "./sample2.py";
char const* pythonArgs[] = {python, "-u", pythonProgram, NULL};
execvp(python, const_cast<char* const*>(pythonArgs));
std::clog << "sample2.py failedn";
std::exit(1);
}
else
{
kids.push_back(pid);
}
}
}
close(fd[0]);
close(fd[1]);
close(fd2[0]);
close(fd2[1]);
for (pid_t k : kids)
{
int status;
//kill (k, SIGTERM);
waitpid(k, &status, 0);
}
}
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