如何让每个子进程输出一个字符串

Question

对于我的任务，我应该"让孩子生成a、b、c和amp；计时，然后让他们生成每个字母的倍数，以查看并发性的作用。使用嵌套循环可以达到，比如每个字母500个">

目前，我的letter_generator.exe程序只是随机选择一封信并打印该信。我下面的程序(主要是我教授的程序，我只是添加了一些东西(创建了1500子进程，这根本不是我认为作业希望我做的。所以，我的问题是如何让每个子进程打印一封特定的信？

#include <windows.h>
#include <iostream>
#include <ctime>
#include <chrono>
using namespace std;
int main(VOID){
STARTUPINFO si;
PROCESS_INFORMATION pi;
// allocate memory
ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
ZeroMemory(&pi, sizeof(pi));

volatile int i = 0;
auto start = chrono::steady_clock::now();
int const CHILD_PROCESS_LIMIT = 1500;
for (i = 0; i < CHILD_PROCESS_LIMIT; i++){
// create child process
if (!CreateProcess(NULL, // use command line
"C:\Users\Coughing\Desktop\letter_generator.exe", // app name
NULL,  // don't inherit process handle
NULL,  // don't inherit thread handle
FALSE, // disable handle inheritance
0,     // no creation flags
NULL,  // use parent's environment block
NULL,  // use parent's existing directory
&si,
&pi)){
fprintf(stderr, "create process failed");
return -1;
}
} 
// parent waits for child to complete
WaitForSingleObject(pi.hProcess, INFINITE);

auto end = chrono::steady_clock::now();
chrono::duration<double> elapsed_seconds = end - start;
cout << "Children Complete in " << elapsed_seconds.count() << " seconds!";
// close handles
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
}

Answer 1

下面是启动子进程并通过命令行向其传递参数的基本示例。

我会把你剩下的家庭作业留给你来解决。

另外请注意，我在这里使用了一些C++17功能，因此，如果您无法编译，请将Visual Studio中的语言标准设置为C++17，或者更改代码以针对您使用的标准版本进行编译。

父进程

#include <iostream>
#include <string>
#include <chrono>
#include <Windows.h>
int main( )
{
std::cout << "Opening processesn";
for( int i = 0; i < 10; i++ ) 
{
STARTUPINFO startup_info{ };
PROCESS_INFORMATION process_info{ };
// To pass arguments to the child process replace 'test'
// with whatever argument you want to pass.
std::wstring args{ L"Child.exe test" };
// create child process
if( !CreateProcessW( 
LR"(C:PathChild.exe)", // use command line
args.data( ),
nullptr,  // don't inherit process handle
nullptr,  // don't inherit thread handle
false,    // disable handle inheritance
0,        // no creation flags
nullptr,  // use parent's environment block
nullptr,  // use parent's existing directory
&startup_info,
&process_info ) ) 
{
std::error_code ec{ static_cast<int>( 
GetLastError( ) ), std::system_category( ) };
std::cerr << "Failed to start process: " << ec.message( ) << 'n';
return -1;
}
std::cout << "Waiting for process to completen";
auto start{ std::chrono::high_resolution_clock::now( ) };
if( auto code{ WaitForSingleObject( 
process_info.hProcess, INFINITE ) }; code != WAIT_OBJECT_0 )
{
std::error_code ec{ static_cast<int>(
GetLastError( ) ), std::system_category( ) };
std::cerr << "Failed to wait for process: " << ec.message( ) << 'n';
}
auto elapsed{ std::chrono::high_resolution_clock::now( ) - start };
auto duration{ std::chrono::duration_cast<std::chrono::microseconds>( elapsed ) };
std::cout << "Time: " << duration.count( ) << " usn";
CloseHandle( process_info.hProcess );
CloseHandle( process_info.hThread );
}
}

子进程

#include <iostream>
int main( int argc, char* argv[ ] )
{
if( argc > 1 )
{
// The argument we passed will be located at index
// 1 in argv.
auto arg{ argv[ 1 ] };
// Prints 'test'.
std::cout << "Argument: " << arg << 'n';
}
}