. 利用标准I/O操作中的fopen、fread、fwrite、fseek、fclose等函数实现文件显示命令cat和 文件复制cp的功能。

1. 文件显示命令cat的实现：

#include <stdio.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s <filename>\n", argv[0]);
        return 1;
    }
    FILE *fp = fopen(argv[1], "r");
    if (fp == NULL) {
        printf("Error opening file %s\n", argv[1]);
        return 1;
    }
    char buffer[BUFSIZ];
    size_t nread;
    while ((nread = fread(buffer, 1, BUFSIZ, fp)) > 0) {
        fwrite(buffer, 1, nread, stdout);
    }
    fclose(fp);
    return 0;
}

2. 文件复制命令cp的实现：

#include <stdio.h>

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("Usage: %s <source> <destination>\n", argv[0]);
        return 1;
    }
    FILE *src = fopen(argv[1], "rb");
    if (src == NULL) {
        printf("Error opening source file %s\n", argv[1]);
        return 1;
    }
    FILE *dst = fopen(argv[2], "wb");
    if (dst == NULL) {
        printf("Error opening destination file %s\n", argv[2]);
        fclose(src);
        return 1;
    }
    char buffer[BUFSIZ];
    size_t nread;
    while ((nread = fread(buffer, 1, BUFSIZ, src)) > 0) {
        fwrite(buffer, 1, nread, dst);
    }
    fclose(src);
    fclose(dst);
    return 0;
}