参数：argc是参数总个数

        argv是数组的指针，例如argv[0]是cp，argv[1]是src.c，argv[2]是dec.c。

思路：

1. 打开src.c
2. 读src.c到buf
3. 打开/创建desc.c
4. 将buf写入des.c
5. close两个文件

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>int main(int argc,char **argv)
{int fdSrc;int fdDes;char *readBuf = NULL;if(argc != 3){printf("pararm error\n");exit(-1);}fdSrc = open(argv[1],O_RDWR);int size = lseek(fdSrc,0,SEEK_END);lseek(fdSrc,0,SEEK_SET);readBuf = (char *)malloc(sizeof(char)*size + 8);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;
}

结果：