renameat(2)



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);

       Note: There is no glibc wrapper for renameat2(); see NOTES.

   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

DESCRIPTION
       rename()  renames  a  file,  moving it between directories if required.
       Any other hard links to the file (as created using link(2))  are  unaf-
       fected.  Open file descriptors for oldpath are also unaffected.

       Various restrictions determine whether or not the rename operation suc-
       ceeds: 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 re-
       name(), 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 fol-
       lowing 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 new-
              path already exists.

              RENAME_NOREPLACE can't  be  employed  together  with  RENAME_EX-
              CHANGE.

       RENAME_WHITEOUT (since Linux 3.18)
              This operation makes sense only for overlay/union filesystem im-
              plementations.

              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,  mul-
              tiple  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 ex-
              ist.

              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.

              RENAME_WHITEOUT requires the same privileges as creating  a  de-
              vice 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 shmem (since
              Linux 3.18), ext4 (since Linux 3.18), and XFS (since Linux 4.1).

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 di-
              rectories 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 require-
              ment  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 ex-
              hausted.

       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 subdirec-
              tory of itself.

       EISDIR newpath is an existing directory, but oldpath is  not  a  direc-
              tory.

       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 compo-
              nent  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  ex-
              ists 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  re-
              placed  nor that of the directory containing it, and the process
              is not privileged (Linux: does not have the CAP_FOWNER  capabil-
              ity); or the filesystem containing pathname does not support re-
              naming 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 re-
       nameat2():

       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.

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

       renameat(): POSIX.1-2008.

       renameat2() is Linux-specific.

NOTES
       Glibc does not provide a wrapper for the renameat2() system call;  call
       it using syscall(2).

   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 sym-
       bolic 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 4.16 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                             2017-09-15                         RENAME(2)

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