Linux系统实验：文件读写1. 分别IO库函数和系统调的方式把从文件读取的内容逐个字符在屏幕上显示，并通过time命令对比执行时间。2. 把10240个大写字母依次写入file.in文件。3. 分别IO库函数和系统调的方式把文件file.in的内容复制到文件file.out，并通过time命令对比执行时间。示例代码及运行结果

很抱歉，我作为一个语言模型AI，并没有办法进行实验操作和文件读写操作。但我可以提供一些示例代码供您参考：

1. 从文件读取内容逐个字符在屏幕上显示

使用IO库函数：

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

int main() {
    FILE* fp;
    char c;

    clock_t start = clock(); // 开始计时

    fp = fopen("file.in", "r");
    if (fp == NULL) {
        printf("Failed to open file\n");
        exit(1);
    }

    while ((c = fgetc(fp)) != EOF) {
        printf("%c", c);
    }

    fclose(fp);

    clock_t end = clock(); // 结束计时
    double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
    printf("\nTime spent: %lf seconds\n", time_spent);

    return 0;
}

使用系统调用：

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

int main() {
    int fd;
    char c;

    clock_t start = clock(); // 开始计时

    fd = open("file.in", O_RDONLY);
    if (fd == -1) {
        printf("Failed to open file\n");
        exit(1);
    }

    while (read(fd, &c, 1) > 0) {
        printf("%c", c);
    }

    close(fd);

    clock_t end = clock(); // 结束计时
    double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
    printf("\nTime spent: %lf seconds\n", time_spent);

    return 0;
}

2. 写入10240个大写字母到file.in文件

使用IO库函数：

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

int main() {
    FILE* fp;
    char c = 'A';
    int i;

    fp = fopen("file.in", "w");
    if (fp == NULL) {
        printf("Failed to open file\n");
        exit(1);
    }

    for (i = 0; i < 10240; i++) {
        fputc(c, fp);
    }

    fclose(fp);

    return 0;
}

使用系统调用：

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

int main() {
    int fd;
    char c = 'A';
    int i;

    fd = open("file.in", O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd == -1) {
        printf("Failed to open file\n");
        exit(1);
    }

    for (i = 0; i < 10240; i++) {
        write(fd, &c, 1);
    }

    close(fd);

    return 0;
}

3. 复制文件file.in的内容到file.out

使用IO库函数：

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

int main() {
    FILE* fp_in;
    FILE* fp_out;
    char c;

    clock_t start = clock(); // 开始计时

    fp_in = fopen("file.in", "r");
    if (fp_in == NULL) {
        printf("Failed to open file.in\n");
        exit(1);
    }

    fp_out = fopen("file.out", "w");
    if (fp_out == NULL) {
        printf("Failed to open file.out\n");
        exit(1);
    }

    while ((c = fgetc(fp_in)) != EOF) {
        fputc(c, fp_out);
    }

    fclose(fp_in);
    fclose(fp_out);

    clock_t end = clock(); // 结束计时
    double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
    printf("Time spent: %lf seconds\n", time_spent);

    return 0;
}

使用系统调用：

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

int main() {
    int fd_in;
    int fd_out;
    char c;
    struct stat st;

    clock_t start = clock(); // 开始计时

    fd_in = open("file.in", O_RDONLY);
    if (fd_in == -1) {
        printf("Failed to open file.in\n");
        exit(1);
    }

    fstat(fd_in, &st);

    fd_out = open("file.out", O_WRONLY | O_CREAT | O_TRUNC, st.st_mode);
    if (fd_out == -1) {
        printf("Failed to open file.out\n");
        exit(1);
    }

    while (read(fd_in, &c, 1) > 0) {
        write(fd_out, &c, 1);
    }

    close(fd_in);
    close(fd_out);

    clock_t end = clock(); // 结束计时
    double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
    printf("Time spent: %lf seconds\n", time_spent);

    return 0;
}