int link(const char *oldpath, const char *newpath);
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.
|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.|
|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.|
|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.
遵循于SVr4, 4.3BSD, POSIX.1-2001 (except as noted above).
BUGSOn 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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