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一、talk命令与本地用户交流

Linux的talk命令是一个视觉通信程序，它将你终端的行复制到另一个用户的终端，就像即时通讯服务一样。Talk命令在Unix-like操作系统中提供了一个文本聊天界面，让你可以实时与其他已登录的用户进行交流。

1.1下载talk及其服务

在Unbuntu20.04LTS中，在终端键入如下命令sudo apt-get install talk以及sudo apt-get install talk-server来下载talk及其服务。

1.2使用talk命令

talk命令的基本语法为talk person [ ttyname]。其中，person可以是你机器上的某个人的登录名，或者是另一台主机上的用户的形式’user@host’。ttyname参数可以指示适当的终端名称，其中ttyname的形式为’ttyXX’或’pts/X’。例如talk user [pts/13]。
若不知道本地用户有哪些以及pts是多少，可以通过who命令进行查询。
实际操作如图
user
talk1

二、自己使用c语言编译代码以实现类似talk功能的程序

思考：这个程序应该支持本地用户之间的实时交流，因此需要一个服务器端来管理连接和转发消息，以及一个客户端来发送和接收消息。因此需要使用两个终端，一个充当服务器，一个充当客户端。

服务器端代码 (talk_server.c)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <pthread.h>#define PORT 9999
#define MAX_CLIENTS 10
#define BUFFER_SIZE 1024int client_sockets[MAX_CLIENTS];
int client_count = 0;// 处理客户端消息的函数
void *handle_client(void *arg) {int client_socket = *((int *)arg);char buffer[BUFFER_SIZE];while (1) {int bytes_received = recv(client_socket, buffer, BUFFER_SIZE, 0);if (bytes_received <= 0) {break;}buffer[bytes_received] = '\0';printf("Received: %s", buffer);// 广播消息给所有其他客户端for (int i = 0; i < client_count; i++) {if (client_sockets[i] != client_socket) {send(client_sockets[i], buffer, strlen(buffer), 0);}}}// 移除断开的客户端for (int i = 0; i < client_count; i++) {if (client_sockets[i] == client_socket) {for (int j = i; j < client_count - 1; j++) {client_sockets[j] = client_sockets[j + 1];}client_count--;break;}}close(client_socket);free(arg);return NULL;
}int main() {int server_socket = socket(AF_INET, SOCK_STREAM, 0);if (server_socket == -1) {perror("Socket creation failed");exit(EXIT_FAILURE);}struct sockaddr_in server_addr;server_addr.sin_family = AF_INET;server_addr.sin_addr.s_addr = INADDR_ANY;server_addr.sin_port = htons(PORT);if (bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {perror("Bind failed");close(server_socket);exit(EXIT_FAILURE);}if (listen(server_socket, MAX_CLIENTS) == -1) {perror("Listen failed");close(server_socket);exit(EXIT_FAILURE);}printf("Server started on port %d. Waiting for connections...\n", PORT);while (1) {struct sockaddr_in client_addr;socklen_t client_len = sizeof(client_addr);int client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &client_len);if (client_socket == -1) {perror("Accept failed");continue;}printf("Accepted connection from %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));// 添加客户端到列表if (client_count < MAX_CLIENTS) {client_sockets[client_count++] = client_socket;// 创建线程处理客户端pthread_t thread;int *client_socket_ptr = malloc(sizeof(int));*client_socket_ptr = client_socket;pthread_create(&thread, NULL, handle_client, client_socket_ptr);pthread_detach(thread);} else {printf("Too many clients. Closing connection.\n");close(client_socket);}}close(server_socket);return 0;
}

客户端代码 (talk_client.c)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <pthread.h>#define PORT 9999
#define BUFFER_SIZE 1024int client_socket;// 接收消息的线程
void *receive_messages(void *arg) {char buffer[BUFFER_SIZE];while (1) {int bytes_received = recv(client_socket, buffer, BUFFER_SIZE, 0);if (bytes_received <= 0) {printf("Connection closed by server.\n");break;}buffer[bytes_received] = '\0';printf("\rReceived: %s\nYou: ", buffer);fflush(stdout);}return NULL;
}// 发送消息的线程
void *send_messages(void *arg) {char buffer[BUFFER_SIZE];while (1) {printf("You: ");fflush(stdout);fgets(buffer, BUFFER_SIZE, stdin);// 去掉换行符buffer[strcspn(buffer, "\n")] = '\0';if (strcmp(buffer, "exit") == 0) {break;}send(client_socket, buffer, strlen(buffer), 0);}return NULL;
}int main() {client_socket = socket(AF_INET, SOCK_STREAM, 0);if (client_socket == -1) {perror("Socket creation failed");exit(EXIT_FAILURE);}struct sockaddr_in server_addr;server_addr.sin_family = AF_INET;server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");server_addr.sin_port = htons(PORT);if (connect(client_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {perror("Connection failed");close(client_socket);exit(EXIT_FAILURE);}printf("Connected to the server. Type 'exit' to quit.\n");pthread_t receive_thread, send_thread;pthread_create(&receive_thread, NULL, receive_messages, NULL);pthread_create(&send_thread, NULL, send_messages, NULL);pthread_join(receive_thread, NULL);pthread_join(send_thread, NULL);close(client_socket);return 0;
}

编译和运行
编译服务器端：gcc talk_server.c -o talk_server -lpthread
编译客户端：gcc talk_client.c -o talk_client -lpthread
启动服务器：./talk_server
在新终端中启动客户端：./talk_client
实际运行

talkc
talc

声明
①该程序仅支持本地通信，不支持跨网络。
②服务器端可以同时处理多个客户端连接。
③客户端之间可以实时发送和接收消息。
④输入 exit 可以退出客户端。

三、参考资料

Linux talk命令教程：如何实时与其他用户进行交流（附实例详解和注意事项）