操作系统上机实验四

实验四匿名管道通信

【实验软硬件环境】

Linux、Win11、GCC

【实验目的与内容】

学习使用匿名管道在两进程间建立通信。

父进程创建一个匿名管道，在父子进程间建立通信

【实验程序及分析】

Windows下

父进程代码father.cpp

#include <windows.h>
#include <process.h>
#include<stdio.h>

int main() {
	HANDLE hParentRead, hParentWrite, hChildRead, hChildWrite;
	
	SECURITY_ATTRIBUTES sa = {0};
	ZeroMemory(&sa, sizeof(SECURITY_ATTRIBUTES));
	sa.bInheritHandle = TRUE;
	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
	
	if (!CreatePipe(&hParentRead, &hChildWrite, &sa, 0)) {
		printf("Pipe failed.");
	}
	if (!CreatePipe(&hChildRead, &hParentWrite, &sa, 0)) {
		printf("Pipe failed.");
	}
	
	STARTUPINFO si = {0};
	ZeroMemory(&si, sizeof(STARTUPINFO));
	si.cb = sizeof(STARTUPINFO);
	si.wShowWindow = SW_SHOWDEFAULT;
	si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
	si.hStdInput = hChildRead;
	si.hStdOutput = hChildWrite;
	si.hStdError = HANDLE(STD_ERROR_HANDLE);
	
	PROCESS_INFORMATION pi = {0};
	
	printf("Create child process...");
	Sleep(50);
	BOOL bSuccess = CreateProcess(TEXT("child.exe"), NULL, NULL, NULL, TRUE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi);
	printf("Send signal? [Y/n]\n");
	char ch;
	scanf("%c",&ch);
	if (ch == 'y' || ch == 'Y') {
		printf("Send signal...\n");
		Sleep(50);
		char buffer[4096] = {'y', 0};
		DWORD dwBytesWritten;
		if (!WriteFile(hParentWrite, buffer, strlen(buffer) * 2, &dwBytesWritten, NULL)) {
			printf("Sent failed");
		}
		printf("Send success.\n");
		Sleep(50);
		
		char result[4096] = {0};
		int flag = 0;
		while (TRUE) {
			memset(result, 0, sizeof(result));
			DWORD dwReadSize;
			if (!ReadFile(hParentRead, result, 4096, &dwReadSize, NULL)) {
				continue;
			}
			if (result[0] == 'e') {
				printf("%s\n", result);
				Sleep(50);
				if (flag < 5) {
					continue;
				}
				else {
					break;
				}
			}
			else {
				printf("Received: %s\n", result);
				Sleep(50);
				++flag;
			}
		}
		printf("Success.");
	}
	CloseHandle(hParentRead);
	CloseHandle(hParentWrite);
	CloseHandle(hChildRead);
	CloseHandle(hChildWrite);
	system("pause");
	return 0;
}

子进程代码child.cpp

#include <windows.h>
#include <process.h>
#include <stdio.h>

int main() {
	printf("Child: Started...");
	Sleep(50);
	HANDLE hRead, hWrite;
	hRead = GetStdHandle(STD_INPUT_HANDLE);
	hWrite = GetStdHandle(STD_OUTPUT_HANDLE);
	
	HANDLE hFile = CreateFile(TEXT("example.txt"), GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, 
								FILE_ATTRIBUTE_NORMAL, NULL);
	if (INVALID_HANDLE_VALUE == hFile) {
		printf("Child: Error");
		Sleep(50);
		CloseHandle(hFile);
	}
	else {
		printf("Child: File handle complete...");
		Sleep(50);
		printf("Child: Waiting for signal...");
		Sleep(50);
		TCHAR str[4096] = {0};
		DWORD dwReadSize;
		while (TRUE) {
			memset(str, 0, sizeof(str));
			
			if (!ReadFile(hRead, str, 4096, &dwReadSize, NULL)) {
				continue;
			}
			
			
			
			if ('y' == str[0]) {
				printf("Child: Received signal...");
				Sleep(50);
				FILE *fp = fopen("example.txt", "r");
				char s[4096] = {0};
				while (fgets(s, 100, fp) != NULL) {
					DWORD dwBytesWritten;
					WriteFile(hWrite, s, 4096, &dwBytesWritten, NULL);
				}
				fclose(fp);
				break;
			}
		}
	}
	printf("Child: Success.");
	Sleep(50);
	CloseHandle(hRead);
	CloseHandle(hWrite);
	CloseHandle(hFile);
	system("pause");
	return 0;
}

代码分析

创建匿名管道

BOOL CreatePipe( 
    PHANDLE hReadPipe, // read handle
	PHANDLE hWritePipe, // write handle
	LPSECURITY_ATTRIBUTES lpPipeAttributes, // security attributes
	DWORD nSize // pipe size
);