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[] = {};
    char dest[] = {};
    int fdr;
    int fdw;
    int ret;
    char buf[] = {};
 
    if(argc != ){
        printf("Usage: %s src.txt dest.txt\n",argv[]);
        return -;
    }
    strcpy(src,argv[]);
    strcpy(dest,argv[]);
 
    /*1.以的方式打开源文件src.txt*/
    fdr = open(src,O_RDONLY);
    if(fdr < ){
        perror("open");
        return -;
    }
 
    /*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,);
    if(fdw < ){
        perror("open");
        return -;
    }
 
    /*3.把src文件的指针移动到文件头*/
    lseek(fdr,,SEEK_SET);
 
    /*3.循环的读取src.txt ,直到结束*/
    while()
    {
        memset(buf,,sizeof(buf));    //清零
        ret = read(fdr,buf,sizeof(buf)-);
        if(ret > ){
 
            /*4.把读到的内容写入到 dest.txt*/
            write(fdw,buf,ret);
        }else if( == ret){
 
            /*读取结束*/
            printf("read over!\n");
            break;
        }else{
            perror("read");
            break;
        }
    }
 
    /*5.关闭*/
    close(fdr);
    close(fdw);
 
    return ;
}