sys_renameat  [fs/namei.c]


Renames a file relative to directory file descriptors, moving it between directories if required.

This system call operates in exactly the same way as sys_rename, except for the differences described below.

Arguments

eax 302
ebx Old directory descriptor.
ecx Pointer to a null-terminated string specifying the old pathname. If it refers to a symbolic link the link is renamed.

If the pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor ebx (rather than relative to the current working directory of the calling process, as is done by sys_rename for a relative pathname).

If the pathname is relative and ebx is the special value AT_FDCWD, then old path is interpreted relative to the current working directory of the calling process.

If the pathname is absolute, then ebx is ignored.
edx New directory descriptor.
esi Pointer to a null-terminated string specifying the new pathname. If it refers to a symbolic link the link is overwritten.

If new path already exists it will be atomically replaced (subject to a few conditions; see 'Return values' below), so that there is no point at which another process attempting to access new path will find it missing.

If new path exists but the operation fails for some reason sys_rename guarantees to leave an instance of new path in place.
However, when overwriting there will probably be a window in which both old path and new path refer to the file being renamed.

If the pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor edx (rather than relative to the current working directory of the calling process, as is done by sys_rename for a relative pathname).

If the pathname is relative and edx is the special value AT_FDCWD, then new path is interpreted relative to the current working directory of the calling process.

If the pathname is absolute, then edx is ignored.

Return values

If the system call succeeds the return value is 0.
If the system call fails the return value is one of the following errno values:

-EACCES Write permission is denied for the directory containing old path or new path, or, search permission is denied for one of the directories in the path prefix of old path or new path, or old path is a directory and does not allow write permission (needed to update the .. entry).
-EBUSY The rename fails because old path or new path is a directory that is in use by some process (perhaps as current working directory, or as root directory, or because it was open for reading) or is in use by the system (for example as mount point), while the system considers this an error. (Note that there is no requirement to return EBUSY in such cases --- there is nothing wrong with doing the rename anyway --- but it is allowed to return EBUSY if the system cannot otherwise handle such situations.)
-EFAULT Old path or new path points outside your accessible address space.
-EINVAL The new pathname contained a path prefix of the old, or, more generally, an attempt was made to make a directory a subdirectory of itself.
-EISDIR New path is an existing directory, but old path is not a directory.
-ELOOP Too many symbolic links were encountered in resolving old path or new path.
-EMLINK Old path already has the maximum number of links to it, or it was a directory and the directory containing new path has the maximum number of links.
-ENAMETOOLONG Old path or new path was too long.
-ENOENT A directory component in old path or new path 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 old path or new path is not, in fact, a directory. Or, old path is a directory, and new path exists but is not a directory.
-or-
Old path is a relative path and ebx is a file descriptor referring to a file other than a directory; or similar for new path and edx.
-ENOTEMPTY,
-EEXIST
New path is a non-empty directory, i.e., contains entries other than "." and "..".
-EPERM,
-EACCES
The directory containing old path has the sticky bit (S_ISVTX) set and the process's effective user ID is neither the user ID of the file to be deleted nor that of the directory containing it, and the process is not privileged (does not have the CAP_FOWNER capability); or new path is an existing file and the directory containing it has the sticky bit set and the process's effective user ID is neither the user ID of the file to be replaced nor that of the directory containing it, and the process is not privileged (does not have the CAP_FOWNER capability); or the filesystem containing pathname does not support renaming of the type requested.
-EROFS The file is on a read-only filesystem.
-EXDEV Old path and new path are not on the same mounted filesystem. (Linux permits a filesystem to be mounted at multiple points, but sys_rename does not work across different mount points, even if the same filesystem is mounted on both.)
-EBADF ebx or edx is not a valid file descriptor.

Remarks

Any other hard links to the file (as created using sys_link) are unaffected.

On NFS filesystems, you can not assume that if the operation failed the file was not renamed. If the server does the rename operation and then crashes, the retransmitted RPC which will be processed when the server is up again causes a failure. The application is expected to deal with this. See sys_link for a similar problem.

Compatibility

Available since 2.6.16.