4-2：实现cp命令

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

#define BUF_SIZE 1024

void cp(char *filename1, char *filename2)
{
        int fd1 = open(filename1, O_RDONLY);
        if (fd1 == -1) {
                printf("fail to open %s:%s
", filename1, strerror(errno));
                return;
        }
        int fd2 = open(filename2, O_WRONLY | O_APPEND | O_CREAT, 0664);
        char szBuf[BUF_SIZE];
        int bytes;
        while(1) {
                memset(szBuf, 0, BUF_SIZE);
                bytes = read(fd1, szBuf, BUF_SIZE);
                if (bytes == 0) {
                        break;
                }
                write(fd2, szBuf, bytes);
        }
}


int main(int argc, char **argv)
{
        if (argc != 3 || !strcmp(argv[1], "--help")) {
                printf("Usage:%s [Src] [Dest]
", argv[0]);
                printf("	Src:Source file
");
                printf("	Dest:Destin file
");
                return 0;
        }
        cp(argv[1], argv[2]);
        return 0;
}

待加强：如果要复制一个包含空洞（连续的空字节）的普通文件，并且要求目标文件的空洞与源文件保持一致。