December 2013
Intermediate to advanced
496 pages
8h 57m
Chinese
Content preview from LINUX系統程式設計 第二版
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檔案與目錄的管理
|
289
另一種連結型態稱為
符號連結
（
symbolic link
）。儘管此類連結不具檔案系統的映射，但
是它具有一個在執行期解譯（interpreted at runtime）的較高階指標。此類連結可以跨檔
案系統—稍後馬上會看到。
硬連結
link()
系統呼叫，原本是 Unix 的一個系統呼叫，不過現在是經過 POSIX 標準化的系統
呼叫，可用於替現存的檔案建立一個新的連結：
#include <unistd.h>
int link (const char *oldpath, const char *newpath);
執行成功時，
link()
會替現存檔案
oldpath
以路徑
newpath
建立一個新的連結，然後會傳
回
0
。完成呼叫後，
oldpath
與
newpath
會指向同一個檔案—事實上，你無法區分哪一個
是最初的連結。
執行失敗時，此呼叫會傳回
-1
而且會把
errno
設定為下面其中一個值：
EACCESS
進行調用之行程對
oldpath
中的一個元件不具搜尋的權限，或者進行調用之行程對包
含
newpath
的目錄不具寫入的權限。
EEXIST
newpath
已經存在—
link()
無法改寫現存的目錄項目。
EFAULT
oldpath
或
newpath
是一個無效的指標。
EIO
發生了一個內部的 I/O 錯誤（這是很嚴重的情況！）。
ELOOP
解析
oldpath
或
newpath
的時候遇到了太多的符號連結。
EMLINK
oldpath
所指向的 inode 已經達到了可以指向它的連結數目上限。 ...
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I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.