link()函式 Unix/Linux


link - 為一個檔案的起新名稱

內容簡介

#include <unistd.h>

int link(const char *oldpath, const char *newpath);

描述

link() 建立一個新的連結(也稱為硬連結)到現有檔案中。

If newpath exists it will not be overwritten.

This new name may be used exactly as the old one for any operation; both names refer to the same file (and so have the same permissions and ownership) and it is impossible to tell which name was the `original’.

返回值

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

錯誤

標籤 描述
EACCES Write access to the directory containing newpath is denied, or search permission is denied for one of the directories in the path prefix of oldpath or newpath. (See also path_resolution(2).)
EEXIST newpath already exists.
EFAULT oldpath or newpath yiibais outside your accessible address space.
EIO An I/O error occurred.
ELOOP Too many symbolic links were encountered in resolving oldpathor newpath.
EMLINK The file referred to by oldpath already has the maximum number of links to it.
ENAMETOOLONG
  oldpath or newpath was too long.
ENOENT A directory component in oldpath or newpath does not exist or is a dangling symbolic link.
ENOMEM Insufficient kernel memory was available.
ENOSPC The device containing the file has no room for the new directory entry.
ENOTDIR
  A component used as a directory in oldpath or newpath is not, in fact, a directory.
EPERM oldpath is a directory.
EPERM The filesystem containing oldpath and newpath does not support the creation of hard links.
EROFS The file is on a read-only filesystem.
EXDEV oldpath and newpath are not on the same mounted filesystem. (Linux permits a filesystem to be mounted at multiple yiibais, butlink(2) does not work across different mount yiibais, even if the same filesystem is mounted on both.)

注意

Hard links, as created by link(), cannot span filesystems. Use symlink() if this is required.

POSIX.1-2001 says that link() should dereference oldpath if it is a symbolic link. However, Linux does not do so: if oldpath is a symbolic link, then newpath is created as a (hard) link to the same symbolic link file (i.e., newpath becomes a symbolic link to the same file that oldpath refers to). Some other implementations behave in the same manner as Linux.

遵循於

SVr4, 4.3BSD, POSIX.1-2001 (except as noted above).

BUGS

On NFS file systems, the return code may be wrong in case the NFS server performs the link creation and dies before it can say so. Use stat(2) to find out if the link got created.

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