Copy file with hole

 Write a utility like cp(1) that copies a file containing holes, without writing the bytes of 0 to the output file.

#include <fcntl.h>#include <stdio.h>#include <unistd.h>#include <string.h>#include <sys/stat.h>#define BSIZE 4096#define RWRWRW (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)int main(int argc, char * argv[]){int srcfd;int destfd;char rdbuf[BSIZE];char wrbuf[BSIZE];ssize_t size;int i;int buf_offset = 0;int hole_offset = 0;if(argc != 3){printf("Input should be like: cp src_file dest_file/n");return;}if((srcfd = open(argv[1],O_RDONLY)) < 0){printf("Open %s error/n",argv[1]);}if((destfd = open(argv[2],O_WRONLY|O_CREAT|O_TRUNC,RWRWRW)) < 0){printf("Creat %s error/n",argv[2]);}while((size = read(srcfd, rdbuf, BSIZE)) > 0){memset(wrbuf,0,BSIZE);i = 0;for(;i<size;i++){if(rdbuf[i] == 0){if(hole_offset == 0 && wrbuf > 0){if(write(destfd,wrbuf,buf_offset)<buf_offset){printf("Write error/n");}buf_offset = 0;memset(wrbuf,0,BSIZE);}hole_offset++;}else if(hole_offset > 0){if(lseek(destfd,hole_offset,SEEK_CUR) < 0){printf("Lseek error/n");}hole_offset = 0;wrbuf[buf_offset++] = rdbuf[i];}else{wrbuf[buf_offset++] = rdbuf[i];}}if( hole_offset > 0){if(lseek(destfd,hole_offset,SEEK_CUR) < 0){printf("Left lseek error/n");}hole_offset = 0;}if( buf_offset > 0){if(write(destfd,wrbuf,buf_offset) < buf_offset){printf("Left write error/n");}buf_offset = 0;}}} 

在copy过程中使用了buffer，测试通过！