renameat

RENAME(2)                  Linux Programmer's Manual                 RENAME(2)



NAME
       rename, renameat, renameat2 - change the name or location of a file

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

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, 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).

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

ERRORS
       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.

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.

CONFORMING TO
       rename(): 4.3BSD, C89, C99, POSIX.1-2001, POSIX.1-2008.

       renameat(): POSIX.1-2008.

       renameat2() is Linux-specific.

NOTES
   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.

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.

SEE ALSO
       mv(1), chmod(2), link(2), symlink(2), unlink(2), path_resolution(7),
       symlink(7)

COLOPHON
       This page is part of release 5.05 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.




Linux                             2019-03-06                         RENAME(2)