在Linux下,C++可以通过多种方式实现进程间通信(IPC),以下是一些常用的IPC机制:
管道(Pipes):
信号(Signals):
消息队列(Message Queues):
共享内存(Shared Memory):
信号量(Semaphores):
套接字(Sockets):
下面是一些简单的示例代码,展示了如何在Linux下使用C++实现这些IPC机制:
// 父进程
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
int main() {
int pipefd[2];
pid_t pid;
char buffer[10];
if (pipe(pipefd) == -1) {
perror("pipe");
exit(EXIT_FAILURE);
}
pid = fork();
if (pid == -1) {
perror("fork");
exit(EXIT_FAILURE);
}
if (pid > 0) { // 父进程
close(pipefd[0]); // 关闭读端
const char* message = "Hello from parent";
write(pipefd[1], message, strlen(message) + 1);
close(pipefd[1]); // 关闭写端
wait(NULL); // 等待子进程结束
} else { // 子进程
close(pipefd[1]); // 关闭写端
read(pipefd[0], buffer, sizeof(buffer));
std::cout << "Child received: " << buffer << std::endl;
close(pipefd[0]); // 关闭读端
}
return 0;
}
// 创建FIFO
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <iostream>
int main() {
const char* fifo = "/tmp/myfifo";
mkfifo(fifo, 0666);
int fd = open(fifo, O_RDWR);
if (fd == -1) {
perror("open");
return 1;
}
const char* message = "Hello from FIFO";
write(fd, message, strlen(message) + 1);
char buffer[10];
read(fd, buffer, sizeof(buffer));
std::cout << "Received: " << buffer << std::endl;
close(fd);
unlink(fifo); // 删除FIFO
return 0;
}
// 使用System V共享内存
#include <sys/ipc.h>
#include <sys/shm.h>
#include <iostream>
#include <cstring>
int main() {
key_t key = ftok("shmfile", 65);
int shmid = shmget(key, 1024, 0666|IPC_CREAT);
char *str = (char*) shmat(shmid, (void*)0, 0);
if (str == (char*)(-1)) {
perror("shmat");
exit(EXIT_FAILURE);
}
strcpy(str, "Hello shared memory");
std::cout << "Shared memory: " << str << std::endl;
shmdt(str);
shmctl(shmid, IPC_RMID, NULL);
return 0;
}
// 使用System V信号量
#include <sys/ipc.h>
#include <sys/sem.h>
#include <iostream>
union semun {
int val;
struct semid_ds *buf;
unsigned short *array;
};
int main() {
key_t key = ftok("semfile", 65);
int semid = semget(key, 1, 0666|IPC_CREAT);
union semun arg;
arg.val = 1; // 初始化信号量为1
semctl(semid, 0, SETVAL, arg);
// P操作(等待信号量)
struct sembuf sb = {0, -1, SEM_UNDO};
semop(semid, &sb, 1);
std::cout << "Semaphore value decreased to " << arg.val << std::endl;
// V操作(释放信号量)
arg.val = 1;
sb.sem_op = 1;
semop(semid, &sb, 1);
semctl(semid, 0, IPC_RMID, arg);
return 0;
}
// 使用Unix Domain Sockets
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <iostream>
#include <cstring>
int main() {
const char* socket_path = "/tmp/uds.sock";
int sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sockfd == -1) {
perror("socket");
return 1;
}
struct sockaddr_un addr;
memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_UNIX;
strncpy(addr.sun_path, socket_path, sizeof(addr.sun_path)-1);
if (bind(sockfd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
perror("bind");
close(sockfd);
return 1;
}
if (listen(sockfd, 5) == -1) {
perror("listen");
close(sockfd);
return 1;
}
int clientfd = accept(sockfd, NULL, NULL);
if (clientfd == -1) {
perror("accept");
close(sockfd);
return 1;
}
char buffer[10];
read(clientfd, buffer, sizeof(buffer));
std::cout << "Server received: " << buffer << std::endl;
const char* message = "Hello from server";
write(clientfd, message, strlen(message) + 1);
close(clientfd);
close(sockfd);
return 0;
}
在使用这些IPC机制时,需要注意同步和互斥的问题,以避免竞态条件和数据不一致。此外,还需要处理错误情况,确保程序的健壮性。
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