dlerror.3: wfix

[thirdparty/man-pages.git] / man2 / rename.2

.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
.\"             and Copyright (C) 1993 Michael Haardt;
.\"             and Copyright (C) 1993,1995 Ian Jackson
.\"		and Copyright (C) 2006, 2014 Michael Kerrisk
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.\" Modified Sat Jul 24 00:35:52 1993 by Rik Faith <faith@cs.unc.edu>
.\" Modified Thu Jun  4 12:21:13 1998 by Andries Brouwer <aeb@cwi.nl>
.\" Modified Thu Mar  3 09:49:35 2005 by Michael Haardt <michael@moria.de>
.\" 2007-03-25, mtk, added various text to DESCRIPTION.
.\"
.TH RENAME 2 2015-07-23 "Linux" "Linux Programmer's Manual"
.SH NAME
rename, renameat, renameat2 \- change the name or location of a file
.SH SYNOPSIS
.nf
.B #include <stdio.h>
.sp
.BI "int rename(const char *" oldpath ", const char *" newpath );
.sp
.BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"
.B #include <stdio.h>
.sp
.BI "int renameat(int " olddirfd ", const char *" oldpath ,
.BI "             int " newdirfd ", const char *" newpath );

.BI "int renameat2(int " olddirfd ", const char *" oldpath ,
.BI "              int " newdirfd ", const char *" newpath \
", unsigned int " flags );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR renameat ():
.PD 0
.ad l
.RS 4
.TP 4
Since glibc 2.10:
_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
.TP
Before glibc 2.10:
_ATFILE_SOURCE
.\" FIXME . need to define FTMs for renameat2(), once it hits glibc
.RE
.ad
.PD
.SH DESCRIPTION
.BR rename ()
renames a file, moving it between directories if required.
Any other hard links to the file (as created using
.BR link (2))
are unaffected.
Open file descriptors for
.I oldpath
are also unaffected.

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

If
.I oldpath
and
.I newpath
are existing hard links referring to the same file, then
.BR rename ()
does nothing, and returns a success status.

If
.I newpath
exists but the operation fails for some reason,
.BR rename ()
guarantees to leave an instance of
.I newpath
in place.

.I oldpath
can specify a directory.
In this case,
.I newpath
must either not exist, or it must specify an empty directory.

However, when overwriting there will probably be a window in which
both
.I oldpath
and
.I newpath
refer to the file being renamed.

If
.I oldpath
refers to a symbolic link, the link is renamed; if
.I newpath
refers to a symbolic link, the link will be overwritten.
.SS renameat()
The
.BR renameat ()
system call operates in exactly the same way as
.BR rename (),
except for the differences described here.

If the pathname given in
.I oldpath
is relative, then it is interpreted relative to the directory
referred to by the file descriptor
.I olddirfd
(rather than relative to the current working directory of
the calling process, as is done by
.BR rename ()
for a relative pathname).

If
.I oldpath
is relative and
.I olddirfd
is the special value
.BR AT_FDCWD ,
then
.I oldpath
is interpreted relative to the current working
directory of the calling process (like
.BR rename ()).

If
.I oldpath
is absolute, then
.I olddirfd
is ignored.

The interpretation of
.I newpath
is as for
.IR oldpath ,
except that a relative pathname is interpreted relative
to the directory referred to by the file descriptor
.IR newdirfd .

See
.BR openat (2)
for an explanation of the need for
.BR renameat ().
.SS renameat2()
.BR renameat2 ()
has an additional
.I flags
argument.
A
.BR renameat2 ()
call with a zero
.I flags
argument is equivalent to
.BR renameat ().

The
.I flags
argument is a bit mask consisting of zero or more of the following flags:
.TP
.B RENAME_EXCHANGE
Atomically exchange
.IR oldpath
and
.IR 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).
.TP
.B RENAME_NOREPLACE
Don't overwrite
.IR newpath
of the rename.
Return an error if
.IR newpath
already exists.

.B RENAME_NOREPLACE
can't be employed together with
.BR RENAME_EXCHANGE .
.TP
.BR RENAME_WHITEOUT " (since Linux 3.18)"
.\" commit 0d7a855526dd672e114aff2ac22b60fc6f155b08
.\" commit 787fb6bc9682ec7c05fb5d9561b57100fbc1cc41
This operation makes sense only for overlay/union
filesystem implementations.

Specifying
.B 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.

.B RENAME_WHITEOUT
requires the same privileges as creating a device node (i.e., the
.BR CAP_MKNOD
capability).

.B RENAME_WHITEOUT
can't be employed together with
.BR RENAME_EXCHANGE .

.B RENAME_WHITEOUT
requires support from the underlying filesystem.
Among the filesystems that provide that support are
shmem (since Linux 3.18),
.\" shmem: commit 46fdb794e3f52ef18b859ebc92f0a9d7db21c5df
ext4 (since Linux 3.18),
.\" ext4: commit cd808deced431b66b5fa4e5c193cb7ec0059eaff
and XFS (since Linux 4.1).
.\" XFS: commit 7dcf5c3e4527cfa2807567b00387cf2ed5e07f00
.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EACCES
Write permission is denied for the directory containing
.I oldpath
or
.IR newpath ,
or, search permission is denied for one of the directories
in the path prefix of
.I oldpath
or
.IR newpath ,
or
.I oldpath
is a directory and does not allow write permission (needed to update
the
.I ..
entry).
(See also
.BR path_resolution (7).)
.TP
.B EBUSY
The rename fails because
.IR 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
.B EBUSY
in such
cases\(emthere is nothing wrong with doing the rename anyway\(embut
it is allowed to return
.B EBUSY
if the system cannot otherwise
handle such situations.)
.TP
.B EDQUOT
The user's quota of disk blocks on the filesystem has been exhausted.
.TP
.B EFAULT
.IR oldpath " or " newpath " points outside your accessible address space."
.TP
.B 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.
.TP
.B EISDIR
.I newpath
is an existing directory, but
.I oldpath
is not a directory.
.TP
.B ELOOP
Too many symbolic links were encountered in resolving
.IR oldpath " or " newpath .
.TP
.B EMLINK
.I oldpath
already has the maximum number of links to it, or
it was a directory and the directory containing
.I newpath
has the maximum number of links.
.TP
.B ENAMETOOLONG
.IR oldpath " or " newpath " was too long."
.TP
.B ENOENT
The link named by
.I oldpath
does not exist;
or, a directory component in
.I newpath
does not exist;
or,
.I oldpath
or
.I newpath
is an empty string.
.TP
.B ENOMEM
Insufficient kernel memory was available.
.TP
.B ENOSPC
The device containing the file has no room for the new directory
entry.
.TP
.B ENOTDIR
A component used as a directory in
.IR oldpath " or " newpath
is not, in fact, a directory.
Or,
.I oldpath
is a directory, and
.I newpath
exists but is not a directory.
.TP
.BR ENOTEMPTY " or " EEXIST
.I newpath
is a nonempty directory, that is, contains entries other than "." and "..".
.TP
.BR EPERM " or " EACCES
The directory containing
.I oldpath
has the sticky bit
.RB ( 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
.B CAP_FOWNER
capability);
or
.I 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
.B CAP_FOWNER
capability);
or the filesystem containing
.I pathname
does not support renaming of the type requested.
.TP
.B EROFS
The file is on a read-only filesystem.
.TP
.B EXDEV
.IR oldpath " and " newpath
are not on the same mounted filesystem.
(Linux permits a filesystem to be mounted at multiple points, but
.BR rename ()
does not work across different mount points,
even if the same filesystem is mounted on both.)
.PP
The following additional errors can occur for
.BR renameat ()
and
.BR renameat2 ():
.TP
.B EBADF
.I olddirfd
or
.I newdirfd
is not a valid file descriptor.
.TP
.B ENOTDIR
.I oldpath
is relative and
.I olddirfd
is a file descriptor referring to a file other than a directory;
or similar for
.I newpath
and
.I newdirfd
.PP
The following additional errors can occur for
.BR renameat2 ():
.TP
.B EEXIST
.I flags
contains
.B RENAME_NOREPLACE
and
.I newpath
already exists.
.TP
.B EINVAL
An invalid flag was specified in
.IR flags .
.TP
.B EINVAL
Both
.B RENAME_NOREPLACE
and
.B RENAME_EXCHANGE
were specified in
.IR flags .
.TP
.B EINVAL
Both
.B RENAME_WHITEOUT
and
.B RENAME_EXCHANGE
were specified in
.IR flags .
.TP
.B EINVAL
The filesystem does not support one of the flags in
.IR flags .
.TP
.B ENOENT
.I flags
contains
.B RENAME_EXCHANGE
and
.IR newpath
does not exist.
.TP
.B EPERM
.B RENAME_WHITEOUT
was specified in
.IR flags ,
but the caller does not have the
.B CAP_MKNOD
capability.
.SH VERSIONS
.BR renameat ()
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.

.BR renameat2 ()
was added to Linux in kernel 3.15.
.\" FIXME . glibc support is pending.
.SH CONFORMING TO
.BR rename ():
4.3BSD, C89, C99, POSIX.1-2001, POSIX.1-2008.

.BR renameat ():
POSIX.1-2008.

.BR renameat2 ()
is Linux-specific.
.SH NOTES
.SS Glibc notes
On older kernels where
.BR renameat ()
is unavailable, the glibc wrapper function falls back to the use of
.BR rename ().
When
.I oldpath
and
.I newpath
are relative pathnames,
glibc constructs pathnames based on the symbolic links in
.IR /proc/self/fd
that correspond to the
.I olddirfd
and
.IR newdirfd
arguments.
.SH 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
.BR link (2)
for a similar problem.
.SH SEE ALSO
.BR mv (1),
.BR chmod (2),
.BR link (2),
.BR symlink (2),
.BR unlink (2),
.BR path_resolution (7),
.BR symlink (7)