Manpage of RENAME

RENAME

Section: Linux Programmer's Manual (2)
Updated: 2016-10-08
Index
 

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
 

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 oldpathare also unaffected.

Various restrictions determine whether or not the rename operation succeeds: see ERRORS below.

If newpathalready exists, it will be atomically replaced, so that there is no point at which another process attempting to access newpathwill find it missing. However, there will probably be a window in which both oldpathand newpathrefer to the file being renamed.

If oldpathand newpathare existing hard links referring to the same file, then rename() does nothing, and returns a success status.

If newpathexists but the operation fails for some reason, rename() guarantees to leave an instance of newpathin place.

oldpathcan specify a directory. In this case, newpathmust either not exist, or it must specify an empty directory.

If oldpathrefers to a symbolic link, the link is renamed; if newpathrefers 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 oldpathis 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 oldpathis relative and olddirfdis the special value AT_FDCWD, then oldpathis interpreted relative to the current working directory of the calling process (like rename()).

If oldpathis absolute, then olddirfdis ignored.

The interpretation of newpathis 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 flagsargument. A renameat2() call with a zero flagsargument is equivalent to renameat().

The flagsargument is a bit mask consisting of zero or more of the following flags:

RENAME_EXCHANGE
Atomically exchange oldpathand 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 newpathof the rename. Return an error if newpathalready exists.

RENAME_NOREPLACEcan't be employed together with RENAME_EXCHANGE.

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

Specifying RENAME_WHITEOUTcreates 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.

RENAME_WHITEOUTrequires the same privileges as creating a device node (i.e., the CAP_MKNODcapability).

RENAME_WHITEOUTcan't be employed together with RENAME_EXCHANGE.

RENAME_WHITEOUTrequires 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 errnois set appropriately.  

ERRORS

EACCES
Write permission is denied for the directory containing oldpathor newpath, or, search permission is denied for one of the directories in the path prefix of oldpathor newpath, or oldpathis 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 newpathis 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 EBUSYin such cases---there is nothing wrong with doing the rename anyway---but it is allowed to return EBUSYif 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
newpathis an existing directory, but oldpathis not a directory.
ELOOP
Too many symbolic links were encountered in resolving oldpath or newpath.
EMLINK
oldpathalready has the maximum number of links to it, or it was a directory and the directory containing newpathhas the maximum number of links.
ENAMETOOLONG
oldpath or newpath was too long.
ENOENT
The link named by oldpathdoes not exist; or, a directory component in newpathdoes not exist; or, oldpathor newpathis 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 newpathis not, in fact, a directory. Or, oldpathis a directory, and newpathexists but is not a directory.
ENOTEMPTY or EEXIST
newpathis a nonempty directory, that is, contains entries other than "." and "..".
EPERM or EACCES
The directory containing oldpathhas 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_FOWNERcapability); or newpathis 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_FOWNERcapability); or the filesystem containing pathnamedoes not support renaming of the type requested.
EROFS
The file is on a read-only filesystem.
EXDEV
oldpath and newpathare 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
olddirfdor newdirfdis not a valid file descriptor.
ENOTDIR
oldpathis relative and olddirfdis a file descriptor referring to a file other than a directory; or similar for newpathand newdirfd

The following additional errors can occur for renameat2():

EEXIST
flagscontains RENAME_NOREPLACEand newpathalready exists.
EINVAL
An invalid flag was specified in flags.
EINVAL
Both RENAME_NOREPLACEand RENAME_EXCHANGEwere specified in flags.
EINVAL
Both RENAME_WHITEOUTand RENAME_EXCHANGEwere specified in flags.
EINVAL
The filesystem does not support one of the flags in flags.
ENOENT
flagscontains RENAME_EXCHANGEand newpathdoes not exist.
EPERM
RENAME_WHITEOUTwas specified in flags, but the caller does not have the CAP_MKNODcapability.
 

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 notes

On older kernels where renameat() is unavailable, the glibc wrapper function falls back to the use of rename(). When oldpathand newpathare relative pathnames, glibc constructs pathnames based on the symbolic links in /proc/self/fdthat correspond to the olddirfdand newdirfdarguments.  

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)


 

Index

NAME
SYNOPSIS
DESCRIPTION
renameat()
renameat2()
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
NOTES
Glibc notes
BUGS
SEE ALSO

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