## seekdir ## 設置下回讀取目錄的位置 ### 相關函數 ### open，opendir，closedir，rewinddir，telldir，readdir，scandir ### 表頭文件 ### ``` #include<dirent.h> ``` ### 定義函數 ### ``` void seekdir(DIR *dir, off_t offset); ``` ### 函數說明 ### seekdir()用來設置參數dir目錄流目前的讀取位置，在調用readdir()時便從此新位置開始讀取。參數offset 代表距離目錄文件開頭的偏移量。 ### 錯誤代碼 ### EBADF 參數dir為無效的目錄流 ### 范例 ### ``` #include<sys/types.h> #include<dirent.h> #include<unistd.h> main() { DIR * dir; struct dirent * ptr; int offset,offset_5,i=0; dir=opendir(“/etc/rc.d”); while((ptr = readdir(dir))!=NULL) { offset = telldir(dir); if(++i = =5) offset_5 =offset; printf(“d_name :%s offset :%d \n”,ptr->d_name,offset); } seekdir(dir offset_5); printf(“Readdir again!\n”); while((ptr = readdir(dir))!=NULL) { offset = telldir(dir); printf(“d_name :%s offset :%d\n”,ptr->d_name.offset); } closedir(dir); } ``` ### 執行 ### ``` d_name : . offset :12 d_name : .. offset:24 d_name : init.d offset 40 d_name : rc0.d offset :56 d_name :rc1.d offset :72 d_name:rc2.d offset :88 d_name:rc3.d offset 104 d_name:rc4.d offset:120 d_name:rc5.d offset:136 d_name:rc6.d offset:152 d_name:rc offset 164 d_name:rc.local offset :180 d_name:rc.sysinit offset :4096 readdir again! d_name:rc2.d offset :88 d_name:rc3.d offset 104 d_name:rc4.d offset:120 d_name:rc5.d offset:136 d_name:rc6.d offset:152 d_name:rc offset 164 d_name:rc.local offset :180 d_name:rc.sysinit offset :4096 ```