cp src.c des.c

实现思路：

1. 打开src.c
2. 读取src.c到buf
3. 打开/创建des.c
4. 将buf写入des.c
5. close文件

int mian()参数介绍：

int main(int argc,char**argv)
{
//argc 表示有几个参数
//argv 数组的指针里面的每一项都是数组
以cp src.c des.c为例

argc = 3
cp argv[0]里面有数组char型cp 2个字符串以此类推 
src.c argv[1]
des.c argv[2]
}

具体代码为例

#include<stdio.h>
int main(int argc, char **argv) 
{
        printf("total params:%d\n",argc);
        printf("NO.1 params:%s\n",argv[0]);
        printf("NO.2 params:%s\n",argv[1]);
        printf("NO.3 params:%s\n",argv[2]);
        return 0;
}

输入./a.out src.c des.c 
返回:
total params:3
NO.1 params:./a.out
NO.2 params:src.c
NO.3 params:des.c

cp 代码的实现：

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char **argv)
{
        int fdSrc;
        int fdDes;
        char *readbuf = NULL;
        if(argc != 3){
                printf("params error\n");
                exit(-1);
        }
        fdSrc = open(argv[1],O_RDWR);
        int size = lseek(fdSrc,0,SEEK_END); //用lseek去读取字节大小
        lseek(fdSrc,0,SEEK_SET);//将光标移动到开头去读内容
        readbuf = (char *)malloc(sizeof(char)*size+1);开辟空间
        memset(readbuf,0,sizeof+1);//初始化赋值
        int n_read = read(fdSrc,readbuf,size);
        fdDes = open(argv[2],O_RDWR|O_CREAT|O_TRUNC,0600);
        int n_write = write(fdDes,readbuf,strlen(readbuf));
        close(fdSrc);
        close(fdDes);
        return 0;
}