lseek()函数的用法
发布时间:2009-11-24 10:41
发布者:李宽
在BT代码的缓冲管理中经常会看到这函数,功能是移动文件的读写指针,可以先在Linux的Sheel下看一下他的函数原型: NAME lseek - reposition read/write file offset SYNOPSIS #include <sys/types.h> #include <unistd.h> off_t lseek(int fd, off_t offset, int whence); DESCRIPTION The lseek() function repositions the offset of the open file associated with the file descriptor fd to the argument offset according to the directive whence as follows: SEEK_SET The offset is set to offset bytes. SEEK_CUR The offset is set to its current location plus offset bytes. SEEK_END 参数说明: fd为已打开的文件描述符; off_t_offset为偏移量,它是根据下面的whence的取值; whence有3种取值: SEEK_SET 将读写位置指向文件头后增加offset个位移量; SEEK_CUR 以目前的读写位置往后增加offset个位移量; SEEK_END 将读写位置指向文件尾后增加offset个位移量; 但是有时候,在旧的代码中可能看到不是SEEK_XXX这样的参数,这是由于新旧值的原因,下面是他们的对应关系: 旧值 新值 0 SEEK_SET 1 SEEK_CUR 2 SEEK_END L_SET SEEK_SET L_INCR SEEK_CUR L_XTND SEEK_END 作者:阿吴网志 2009-11-23 |
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