文件I/O实现cp复制功能

copy.c:

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

//a.out   src.txt dest.txt
//argv[0] argv[1] argv[2]
int main(int argc,char *argv[])
{
    char src[20] = {0};
    char dest[20] = {0};
    int fdr;
    int fdw;
    int ret;
    char buf[1024] = {0};

    if(argc != 3){
        printf("Usage: %s src.txt dest.txt
",argv[0]);
        return -1;
    }
    strcpy(src,argv[1]);
    strcpy(dest,argv[2]);

    /*1.以的方式打开源文件src.txt*/
    fdr = open(src,O_RDONLY);
    if(fdr < 0){
        perror("open");
        return -1;
    }

    /*2.以写的方式打开目标文件 dest.txt ,如果不存在，则创建*/
    fdw = open(dest,O_WRONLY | O_CREAT,0755);
    if(fdw < 0){
        perror("open");
        return -1;
    }
    
    /*3.把src文件的指针移动到文件头*/
    lseek(fdr,0,SEEK_SET);

    /*3.循环的读取src.txt ,直到结束*/
    while(1)
    {
        memset(buf,0,sizeof(buf));    //清零
        ret = read(fdr,buf,sizeof(buf)-1);
        if(ret > 0){
            
            /*4.把读到的内容写入到 dest.txt*/
            write(fdw,buf,ret);
        }else if(0 == ret){

            /*读取结束*/
            printf("read over!
");
            break;
        }else{
            perror("read");
            break;
        }
    }

    /*5.关闭*/
    close(fdr);
    close(fdw);
    
    return 0;
}