изменить имя или расположение файла (change the name or location of a file)
Имя (Name)
rename, renameat, renameat2 - change the name or location of a
file
Синопсис (Synopsis)
#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():
_GNU_SOURCE
Описание (Description)
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.
renameat()
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()
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, tmpfs, and cifs (Linux 3.17);
* xfs (Linux 4.0);
* Support for many other filesystems was added in Linux
4.9, including ext2, 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 support it 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).
Возвращаемое значение (Return value)
On success, zero is returned. On error, -1 is returned, and
errno is set to indicate the error.
Ошибки (Error)
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 a
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 oldpath 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 oldpath (newpath) is relative but olddirfd (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.
Версии (Versions)
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.
Стандарты (Conforming to)
rename(): 4.3BSD, C89, C99, POSIX.1-2001, POSIX.1-2008.
renameat(): POSIX.1-2008.
renameat2() is Linux-specific.
Примечание (Note)
Glibc notes
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.
Ошибки (баги) (Bugs)
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.
Смотри также (See also)
mv(1), rename(1), chmod(2), link(2), symlink(2), unlink(2),
path_resolution(7), symlink(7)
