C语言实现write命令.并基于linux文件系统和who命令的c语言实现方法实现不同用户间的通信

实现write命令的C语言代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>

int main(int argc, char *argv[]) {
    if (argc < 3) {
        fprintf(stderr, "Usage: %s user message\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    char *user = argv[1];
    char *msg = argv[2];
    char *pipe_name = malloc(strlen(user) + 6);
    sprintf(pipe_name, "/tmp/%s.pipe", user);

    if (mkfifo(pipe_name, 0666) == -1) {
        if (errno != EEXIST) {
            fprintf(stderr, "Failed to create pipe: %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }
    }

    int fd = open(pipe_name, O_WRONLY);
    if (fd == -1) {
        fprintf(stderr, "Failed to open pipe: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    if (write(fd, msg, strlen(msg)) == -1) {
        fprintf(stderr, "Failed to write to pipe: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    close(fd);
    free(pipe_name);
    exit(EXIT_SUCCESS);
}

基于Linux文件系统和who命令的C语言实现方法实现不同用户间的通信:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>

#define MAX_USERS 10

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s user\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    char *user = argv[1];
    char *pipe_name = malloc(strlen(user) + 6);
    sprintf(pipe_name, "/tmp/%s.pipe", user);

    if (mkfifo(pipe_name, 0666) == -1) {
        if (errno != EEXIST) {
            fprintf(stderr, "Failed to create pipe: %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }
    }

    int fds[MAX_USERS];
    for (int i = 0; i < MAX_USERS; i++) {
        if (i == getpid() % MAX_USERS) {
            fds[i] = -1; // skip own pipe
            continue;
        }

        char *other_user = malloc(10);
        sprintf(other_user, "user%d", i);
        char *other_pipe_name = malloc(strlen(other_user) + 6);
        sprintf(other_pipe_name, "/tmp/%s.pipe", other_user);

        fds[i] = open(other_pipe_name, O_WRONLY | O_NONBLOCK); // open non-blocking

        if (fds[i] == -1) {
            if (errno != ENXIO) { // ignore non-existent pipes
                fprintf(stderr, "Failed to open pipe: %s\n", strerror(errno));
                exit(EXIT_FAILURE);
            }
        }

        free(other_user);
        free(other_pipe_name);
    }

    char buf[1024];
    int read_fd = open(pipe_name, O_RDONLY | O_NONBLOCK); // open non-blocking
    if (read_fd == -1) {
        fprintf(stderr, "Failed to open read pipe: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    while (1) {
        int n = read(read_fd, buf, sizeof(buf));
        if (n == -1) {
            if (errno == EAGAIN) {
                usleep(100000); // sleep for 100ms if no data available
                continue;
            } else {
                fprintf(stderr, "Failed to read from pipe: %s\n", strerror(errno));
                exit(EXIT_FAILURE);
            }
        } else if (n == 0) {
            break; // pipe closed
        } else {
            buf[n] = '\0';
            printf("%s", buf);

            for (int i = 0; i < MAX_USERS; i++) {
                if (fds[i] != -1) {
                    if (write(fds[i], buf, n) == -1) {
                        fprintf(stderr, "Failed to write to pipe: %s\n", strerror(errno));
                        exit(EXIT_FAILURE);
                    }
                }
            }
        }
    }

    close(read_fd);
    free(pipe_name);
    exit(EXIT_SUCCESS);
}

代码使用了非阻塞方式打开管道，以便在没有数据可读/写时不会阻塞。在实际应用中，应该使用多线程或异步IO等方法来避免阻塞。