【Linux】进程间通信上 （1.5万字详解）

#include<unistd.h>

/* @param fd,经参数fd返回的两个文件描述符
 * fd[0]为读而打开，fd[1]为写而打开
 * fd[1]的输出是fd[0]的输入
 * @return 若成功，返回0；若出错，返回-1并设置errno
 */
int pipe(int fd[2]);

#include <iostream>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <cassert>
#include<cstring>
int main()
{
    // 创建管道
    int fd[2];
    int n = pipe(fd);
    assert(n == 0);
    // fd[0]为读端
    // fd[1]为写端

    // 创建子进程
    pid_t fds = fork();
    assert(fds >= 0);
    const char *msg = "我是子进程，我正在给你发消息";
    int cnt = 0;
    if (fds == n)
    {
        // 子进程
        // 关闭文件描述符
        // 子进程进行写入
        while (1)
        {
            cnt++;
            close(fd[0]);
            char buffer[1024];
            snprintf(buffer, sizeof buffer, "子进程->父进程:%d[%s]", cnt, msg);
            write(fd[1], buffer, strlen(buffer));
            sleep(1);
        }
        exit(1);
    }
    close(fd[1]);
    char readbuffer[1024];
    while(1)
    {
        read(fd[0],readbuffer,sizeof readbuffer-1);
        std::cout<<readbuffer<<std::endl;
        sleep(1);
    }
  
    int m = waitpid(fds, nullptr, 0);
    assert(m = fds);
}

#include <iostream>
#include <string>
#include <vector>
#include <cstdlib>
#include <cassert>
#include <ctime>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#define MakeSeed() srand((unsigned long)time(nullptr) ^ getpid() ^ 0x171237 ^ rand() % 1234)

#define PROCSS_NUM 10

///子进程要完成的某种任务 -- 模拟一下/
// 函数指针 类型
typedef void (*func_t)();

void downLoadTask()
{
    std::cout << getpid() << ": 下载任务\n"
              << std::endl;
    sleep(1);
}

void ioTask()
{
    std::cout << getpid() << ": IO任务\n"
              << std::endl;
    sleep(1);
}

void flushTask()
{
    std::cout << getpid() << ": 刷新任务\n"
              << std::endl;
    sleep(1);
}

void loadTaskFunc(std::vector<func_t> *out)
{
    assert(out);
    out->push_back(downLoadTask);
    out->push_back(ioTask);
    out->push_back(flushTask);
}

/下面的代码是一个多进程程序//
class subEp // Endpoint
{
public:
    subEp(pid_t subId, int writeFd)
        : subId_(subId), writeFd_(writeFd)
    {
        char nameBuffer[1024];
        snprintf(nameBuffer, sizeof nameBuffer, "process-%d[pid(%d)-fd(%d)]", num++, subId_, writeFd_);
        name_ = nameBuffer;
    }

public:
    static int num;
    std::string name_;
    pid_t subId_;
    int writeFd_;
};

int subEp::num = 0;

int recvTask(int readFd)
{
    int code = 0;
    ssize_t s = read(readFd, &code, sizeof code);
    if(s == 4) return code;
    else if(s <= 0) return -1;
    else return 0;
}

void sendTask(const subEp &process, int taskNum)
{
    std::cout << "send task num: " << taskNum << " send to -> " << process.name_ << std::endl;
    int n = write(process.writeFd_, &taskNum, sizeof(taskNum));
    assert(n == sizeof(int));
    (void)n;
}

void createSubProcess(std::vector<subEp> *subs, std::vector<func_t> &funcMap)
{
    std::vector<int> deleteFd;
    for (int i = 0; i < PROCSS_NUM; i++)
    {
        int fds[2];
        int n = pipe(fds);
        assert(n == 0);
        (void)n;
        // 父进程打开的文件，是会被子进程共享的
        // 你试着多想几轮
        pid_t id = fork();
        if (id == 0)
        {
            for(int i = 0; i < deleteFd.size(); i++) close(deleteFd[i]);
            // 子进程, 进行处理任务
            close(fds[1]);
            while (true)
            {
                // 1. 获取命令码，如果没有发送，我们子进程应该阻塞
                int commandCode = recvTask(fds[0]);
                // 2. 完成任务
                if (commandCode >= 0 && commandCode < funcMap.size())
                    funcMap[commandCode]();
                else if(commandCode == -1) break;
            }
            exit(0);
        }
        close(fds[0]);
        subEp sub(id, fds[1]);
        subs->push_back(sub);
        deleteFd.push_back(fds[1]);
    }
}

void loadBlanceContrl(const std::vector<subEp> &subs, const std::vector<func_t> &funcMap, int count)
{
    int processnum = subs.size();
    int tasknum = funcMap.size();
    bool forever = (count == 0 ? true : false);

    while (true)
    {
        // 1. 选择一个子进程 --> std::vector<subEp> -> index - 随机数
        int subIdx = rand() % processnum;
        // 2. 选择一个任务 --> std::vector<func_t> -> index
        int taskIdx = rand() % tasknum;
        // 3. 任务发送给选择的进程
        sendTask(subs[subIdx], taskIdx);
        sleep(1);
        if(!forever)
        {
            count--;
            if(count == 0) break;   
        }
    }
    // write quit -> read 0
    for(int i = 0; i < processnum; i++) close(subs[i].writeFd_); // waitpid();
}

    
void waitProcess(std::vector<subEp> processes)
{
    int processnum = processes.size();
    for(int i = 0; i < processnum; i++)
    {
        waitpid(processes[i].subId_, nullptr, 0);
        std::cout << "wait sub process success ...: " << processes[i].subId_ << std::endl;
    }
}

int main()
{
    MakeSeed();
    // 1. 建立子进程并建立和子进程通信的信道, 有bug的，但是不影响我们后面编写
    // 1.1 加载方发表
    std::vector<func_t> funcMap;
    loadTaskFunc(&funcMap);
    // 1.2 创建子进程，并且维护好父子通信信道
    std::vector<subEp> subs;
    createSubProcess(&subs, funcMap);

    // 2. 走到这里就是父进程, 控制子进程，负载均衡的向子进程发送命令码
    int taskCnt = 3; // 0: 永远进行
    loadBlanceContrl(subs, funcMap, taskCnt);

    // 3. 回收子进程信息
    waitProcess(subs);

    return 0;
}

#include "comm.hpp"

// 你可不可以把刚刚写的改成命名管道呢！
int main()
{
    std::cout << "client begin" << std::endl;
    int wfd = open(NAMED_PIPE, O_WRONLY);
    std::cout << "client end" << std::endl;
    if(wfd < 0) exit(1); 

    //write
    char buffer[1024];
    while(true)
    {
        std::cout << "Please Say# ";
        fgets(buffer, sizeof(buffer), stdin); // abcd\n
        if(strlen(buffer) > 0) buffer[strlen(buffer)-1] = 0;
        ssize_t n = write(wfd, buffer, strlen(buffer));
        assert(n == strlen(buffer));
        (void)n;
    }

    close(wfd);
    return 0;
}

#include "comm.hpp"

int main()
{
    bool r = createFifo(NAMED_PIPE);
    assert(r);
    (void)r;

    std::cout << "server begin" << std::endl;
    int rfd = open(NAMED_PIPE, O_RDONLY);
    std::cout << "server end" << std::endl;
    if(rfd < 0) exit(1);

    //read
    char buffer[1024];
    while(true)
    {
        ssize_t s = read(rfd, buffer, sizeof(buffer)-1);
        if(s > 0)
        {
            buffer[s] = 0;
            std::cout << "client->server# " << buffer << std::endl;
        }
        else if(s == 0)
        {
            std::cout << "client quit, me too!" << std::endl;
            break;
        }
        else
        {
            std::cout << "err string: " << strerror(errno) << std::endl;
            break;
        }
    }

    close(rfd);

    // sleep(10);
    removeFifo(NAMED_PIPE);
    return 0;
}

#pragma once
#include<iostream>
#include<string>
#include<cstring>
#include<cerrno>
#include<assert.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>

#define NAMED_PIPE "/home/user/exercise/my_pipe/named_pipe/name_pipe"
bool createFiFo(const std::string &path)
{
    umask(0);
    int n=mkfifo(path.c_str(),0600);
    if(n==0)
    {
        return true;
    }
    else
    {
        std::cout<<"errno:"<<errno<<"err string"<<strerror(errno)<<std::endl;

    }
}
void deleteFifo(const std::string &path)
{
    int n=unlink(path.c_str());
    assert(n==0);
     (void)n;
}

.PHONY:all
all:client server
client:client.cc
	g++ -o $@ $^ -std=c++11
server:server.cc
	g++ -o $@ $^ -std=c++11
.PHONY:clean
clean:
	rm -f client server

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cerrno>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string>
#include <unistd.h>
#include <cassert>

#define SHM_SIZE 4096
#define PATH_NAME ".fifo"
#define PROJ_ID 0x14

#define FIFO_FILE ".fifo"

// 创建命名管道文件
void CreatFifo() {
    umask(0);
    if(mkfifo(FIFO_FILE, 0666) < 0)
    {
        std::cerr << strerror(errno) << std::endl;
        exit(-1);
    }
}

#define READER O_RDONLY
#define WRITER O_WRONLY

// 以一定的方式打开管道文件
int Open(const std::string &filename, int flags)
{
    return open(filename.c_str(), flags);
}

// 用于服务端, 等待读取管道文件数据, 即读取信号
int Wait(int fd) {
    uint32_t value = 0;
    ssize_t res = read(fd, &value, sizeof(value));
    
    return res;
}

// 用于客户端, 向管道中写入数据, 即写入信号
void Signal(int fd) {
    uint32_t cmd = 1;
    write(fd, &cmd, sizeof(cmd));
}

// 关闭管道文件, 删除管道文件
void Close(int fd, const std::string& filename) {
    close(fd);
    unlink(filename.c_str());
}

// ipcShmServer 服务端代码, 即 接收端
// 需要创建、删除共享内存块
// 需要创建、删除命名管道
#include "common.hpp"
using std::cout;
using std::endl;
using std::cerr;

int main() {
    // 0. 创建命名管道
    CreatFifo();
    int fd = Open(FIFO_FILE, READER);       // 只读打开命名管道
    assert(fd >= 0);

    // 1. 创建共享内存块
    int key = ftok(PATH_NAME, PROJ_ID);
    if(key == -1) {
        cerr << "ftok error. " << strerror(errno) << endl;
        exit(1);
    }

    cout << "Create share memory begin. " << endl;
    int shmId = shmget(key, SHM_SIZE, IPC_CREAT | IPC_EXCL | 0666);
    if(shmId == -1) {
        cerr << "shmget error" << endl;
        exit(2);
    }
    cout << "Creat share memory success, key: " << key << " , shmId: " << shmId << endl;

    // 2. 连接共享内存块
    sleep(2);
    char* str = (char*)shmat(shmId, nullptr, 0);
    if(str == (void*)-1) {
        cerr << "shmat error" << endl;
        exit(3);
    }
    cout << "Attach share memory success. \n" << endl;

    // 3. 使用共享内存块
    while(true) {
        if (Wait(fd) <= 0)
            break;              // 如果从管道读取数据失败, 或管道文件关闭, 则退出循环
        
        cout << str;
        sleep(1);
    }
    cout << "\nThe server has finished using shared memory. " << endl;

    sleep(1);
    // 3. 分离共享内存块
    int resDt = shmdt(str);
    if(resDt == -1) {
        cerr << "shmdt error" << endl;
        exit(4);
    }
    cout << "Detach share memory success. \n" << endl;

    // 4. 删除共享内存块
    int res = shmctl(shmId, IPC_RMID, nullptr);
    if(res == -1) {
        cerr << "shmget error" << endl;
        exit(5);
    }
    cout << "Delete share memory success. " << endl;

    // 5. 删除管道文件
    Close(fd, FIFO_FILE);
    cout << "Delete FIFO success. " << endl;

    return 0;
}

// ipcShmClient 客户端代码, 即 发送端
// 不参与共享内存块的创建与删除
// 不参与命名管道的创建与删除
#include "common.hpp"
using std::cout;
using std::endl;
using std::cerr;

int main() {
    // 0. 打开命名管道
    int fd = Open(FIFO_FILE, WRITER);

    // 1. 获取共享内存块
    int key = ftok(PATH_NAME, PROJ_ID);
    if(key == -1) {
        cerr << "ftok error. " << strerror(errno) << endl;
        exit(1);
    }
    cout << "Get share memory begin. " << endl;
    sleep(1);
    int shmId = shmget(key, SHM_SIZE, IPC_CREAT);
    if(shmId == -1) {
        cerr << "shmget error" << endl;
        exit(2);
    }
    cout << "Creat share memory success, key: " << key << " , shmId: " << shmId << endl;

    // 2. 连接共享内存块
    sleep(2);
    char* str = (char*)shmat(shmId, nullptr, 0);
    if(str == (void*)-1) {
        cerr << "shmat error" << endl;
        exit(3);
    }
    cout << "Attach share memory success. " << endl;

    // 3. 使用共享内存块
    while (true) {
        printf("Please Enter $ ");
        fflush(stdout);
        ssize_t res = read(0, str, SHM_SIZE);       // 从标准输入读取数据写入到 共享内存(str) 中
        if(res > 0) {
            str[res] = '\0';
        }

        Signal(fd);     // 向命名管道写入信号
    }
    cout << "\nThe client has finished using shared memory. " << endl;

    // 3. 分离共享内存块
    int res = shmdt(str);
    if(res == -1) {
        cerr << "shmdt error" << endl;
        exit(4);
    }
    cout << "Detach share memory success. " << endl;

    return 0;
}

.PHONY:all
all:ipcShmClient ipcShmServer

ipcShmClient:ipcShmClient.cpp
	g++ $^ -o $@
ipcShmServer:ipcShmServer.cpp
	g++ $^ -o $@

.PHONY:clean
clean:
	rm -f ipcShmClient ipcShmServer .fifo