rename, renameat, renameat2 - change the name or location of a file
#include <stdio.h>
int rename(const char *oldpath, const char *newpath);
#include <fcntl.h> /* Definition of AT_* constants */
#include <stdio.h>
int renameat(int olddirfd, const char *oldpath,
int newdirfd, const char *newpath);
int renameat2(int olddirfd, const char *oldpath,
int newdirfd, const char *newpath, unsigned int flags);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
renameat():
- Since glibc 2.10:
- _POSIX_C_SOURCE >= 200809L
- Before glibc 2.10:
- _ATFILE_SOURCE
renameat2():
rename() renames a file, moving it between directories if required. Any
other hard links to the file (as created using
link(2)) are unaffected.
Open file descriptors for
oldpath are also unaffected.
Various restrictions determine whether or not the rename operation succeeds: see
ERRORS below.
If
newpath already exists, it will be atomically replaced, so that there
is no point at which another process attempting to access
newpath will
find it missing. However, there will probably be a window in which both
oldpath and
newpath refer to the file being renamed.
If
oldpath and
newpath are existing hard links referring to the
same file, then
rename() does nothing, and returns a success status.
If
newpath exists but the operation fails for some reason,
rename() guarantees to leave an instance of
newpath in place.
oldpath can specify a directory. In this case,
newpath must either
not exist, or it must specify an empty directory.
If
oldpath refers to a symbolic link, the link is renamed; if
newpath refers to a symbolic link, the link will be overwritten.
The
renameat() system call operates in exactly the same way as
rename(), except for the differences described here.
If the pathname given in
oldpath is relative, then it is interpreted
relative to the directory referred to by the file descriptor
olddirfd
(rather than relative to the current working directory of the calling process,
as is done by
rename() for a relative pathname).
If
oldpath is relative and
olddirfd is the special value
AT_FDCWD, then
oldpath is interpreted relative to the current
working directory of the calling process (like
rename()).
If
oldpath is absolute, then
olddirfd is ignored.
The interpretation of
newpath is as for
oldpath, except that a
relative pathname is interpreted relative to the directory referred to by the
file descriptor
newdirfd.
See
openat(2) for an explanation of the need for
renameat().
renameat2() has an additional
flags argument. A
renameat2()
call with a zero
flags argument is equivalent to
renameat().
The
flags argument is a bit mask consisting of zero or more of the
following flags:
- RENAME_EXCHANGE
- Atomically exchange oldpath and newpath. Both pathnames must
exist but may be of different types (e.g., one could be a non-empty
directory and the other a symbolic link).
- RENAME_NOREPLACE
- Don't overwrite newpath of the rename. Return an error if
newpath already exists.
- RENAME_NOREPLACE can't be employed together with
RENAME_EXCHANGE.
- RENAME_NOREPLACE requires support from the underlying filesystem.
Support for various filesystems was added as follows:
- *
- ext4 (Linux 3.15);
- *
- btrfs, shmem, and cifs (Linux 3.17);
- *
- xfs (Linux 4.0);
- *
- Support for many other filesystems was added in Linux 4.9, including etx2,
minix, reiserfs, jfs, vfat, and bpf.
- RENAME_WHITEOUT (since Linux 3.18)
- This operation makes sense only for overlay/union filesystem
implementations.
- Specifying RENAME_WHITEOUT creates a "whiteout" object at
the source of the rename at the same time as performing the rename. The
whole operation is atomic, so that if the rename succeeds then the
whiteout will also have been created.
- A "whiteout" is an object that has special meaning in
union/overlay filesystem constructs. In these constructs, multiple layers
exist and only the top one is ever modified. A whiteout on an upper layer
will effectively hide a matching file in the lower layer, making it appear
as if the file didn't exist.
- When a file that exists on the lower layer is renamed, the file is first
copied up (if not already on the upper layer) and then renamed on the
upper, read-write layer. At the same time, the source file needs to be
"whiteouted" (so that the version of the source file in the
lower layer is rendered invisible). The whole operation needs to be done
atomically.
- When not part of a union/overlay, the whiteout appears as a character
device with a {0,0} device number. (Note that other union/overlay
implementations may employ different methods for storing whiteout entries;
specifically, BSD union mount employs a separate inode type,
DT_WHT, which, while supported by some filesystems available in
Linux, such as CODA and XFS, is ignored by the kernel's whiteout support
code, as of Linux 4.19, at least.)
- RENAME_WHITEOUT requires the same privileges as creating a device
node (i.e., the CAP_MKNOD capability).
- RENAME_WHITEOUT can't be employed together with
RENAME_EXCHANGE.
- RENAME_WHITEOUT requires support from the underlying filesystem.
Among the filesystems that provide that support are tmpfs (since Linux
3.18), ext4 (since Linux 3.18), XFS (since Linux 4.1), f2fs (since Linux
4.2). btrfs (since Linux 4.7), and ubifs (since Linux 4.9).
On success, zero is returned. On error, -1 is returned, and
errno is set
appropriately.
- EACCES
- Write permission is denied for the directory containing oldpath or
newpath, or, search permission is denied for one of the directories
in the path prefix of oldpath or newpath, or oldpath
is a directory and does not allow write permission (needed to update the
.. entry). (See also path_resolution(7).)
- EBUSY
- The rename fails because oldpath or newpath 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.)
- EDQUOT
- The user's quota of disk blocks on the filesystem has been exhausted.
- EFAULT
- oldpath or newpath 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
- newpath is an existing directory, but oldpath is not a
directory.
- ELOOP
- Too many symbolic links were encountered in resolving oldpath or
newpath.
- EMLINK
- oldpath already has the maximum number of links to it, or it was a
directory and the directory containing newpath has the maximum
number of links.
- ENAMETOOLONG
- oldpath or newpath was too long.
- ENOENT
- The link named by oldpath does not exist; or, a directory component
in newpath does not exist; or, oldpath or newpath is
an empty string.
- 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. Or, oldpath is a directory, and
newpath exists but is not a directory.
- ENOTEMPTY or EEXIST
- newpath is a nonempty directory, that is, contains entries other
than "." and "..".
- EPERM or EACCES
- The directory containing oldpath 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 (Linux: does not have the
CAP_FOWNER capability); or newpath 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
(Linux: 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
- oldpath and newpath are not on the same mounted filesystem.
(Linux permits a filesystem to be mounted at multiple points, but
rename() does not work across different mount points, even if the
same filesystem is mounted on both.)
The following additional errors can occur for
renameat() and
renameat2():
- EBADF
- olddirfd or newdirfd is not a valid file descriptor.
- ENOTDIR
- oldpath is relative and olddirfd is a file descriptor
referring to a file other than a directory; or similar for newpath
and newdirfd
The following additional errors can occur for
renameat2():
- EEXIST
- flags contains RENAME_NOREPLACE and newpath already
exists.
- EINVAL
- An invalid flag was specified in flags.
- EINVAL
- Both RENAME_NOREPLACE and RENAME_EXCHANGE were specified in
flags.
- EINVAL
- Both RENAME_WHITEOUT and RENAME_EXCHANGE were specified in
flags.
- EINVAL
- The filesystem does not support one of the flags in flags.
- ENOENT
- flags contains RENAME_EXCHANGE and newpath does not
exist.
- EPERM
- RENAME_WHITEOUT was specified in flags, but the caller does
not have the CAP_MKNOD capability.
renameat() was added to Linux in kernel 2.6.16; library support was added
to glibc in version 2.4.
renameat2() was added to Linux in kernel 3.15; library support was added
in glibc 2.28.
rename(): 4.3BSD, C89, C99, POSIX.1-2001, POSIX.1-2008.
renameat(): POSIX.1-2008.
renameat2() is Linux-specific.
On older kernels where
renameat() is unavailable, the glibc wrapper
function falls back to the use of
rename(). When
oldpath and
newpath are relative pathnames, glibc constructs pathnames based on the
symbolic links in
/proc/self/fd that correspond to the
olddirfd
and
newdirfd arguments.
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
link(2) for
a similar problem.
mv(1),
chmod(2),
link(2),
symlink(2),
unlink(2),
path_resolution(7),
symlink(7)