在向不可写内存写入时，根据表示文件、匿名管道或套接字的文件描述符，read()的行为会有所不同

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("non_writable_file.txt", O_RDONLY);
    if (fd == -1) {
        perror("Error opening file");
        return 1;
    }

    char buffer[100];
    ssize_t bytesRead = read(fd, buffer, sizeof(buffer));
    if (bytesRead == -1) {
        perror("Error reading file");
        close(fd);
        return 1;
    }

    buffer[bytesRead] = '\0';
    printf("Read %ld bytes: %s\n", bytesRead, buffer);

    close(fd);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main() {
    int pipefd[2];
    if (pipe(pipefd) == -1) {
        perror("pipe");
        exit(EXIT_FAILURE);
    }

    pid_t pid = fork();
    if (pid == -1) {
        perror("fork");
        exit(EXIT_FAILURE);
    } else if (pid == 0) { // Child process
        close(pipefd[0]); // Close reading end in child
        write(pipefd[1], "Hello, World!", 13);
        close(pipefd[1]);
        exit(EXIT_SUCCESS);
    }

    close(pipefd[1]); // Close writing end in parent
    char buffer[100];
    ssize_t bytesRead = read(pipefd[0], buffer, sizeof(buffer));
    if (bytesRead == -1) {
        perror("read");
        exit(EXIT_FAILURE);
    }

    buffer[bytesRead] = '\0';
    printf("Read %ld bytes: %s\n", bytesRead, buffer);

    close(pipefd[0]);
    return 0;
}