RENAME(2) System Calls Manual RENAME(2)

rename, renameat — change the name of a file

Standard C Library (libc, -lc)

#include <stdio.h>

int
rename(const char *from, const char *to);

#include <unistd.h>

int
renameat(int fromfd, const char *from, int tofd, const char *to);

() causes the link named from to be renamed as to. If to exists, it is first removed. Both from and to must be of the same type (that is, both directories or both non-directories), and must reside on the same file system.

() guarantees that an instance of to will always exist, even if the system should crash in the middle of the operation.

If the final component of from is a symbolic link, the symbolic link is renamed, not the file or directory to which it points.

If both from and to refer to the same name in the same directory, () returns successfully and performs no other action.

() works the same way as rename() except if from (resp. to) is relative. In that case, it is looked up from a directory whose file descriptor was passed as fromfd (resp. tofd). Search permission is required on the directories named by fromfd and tofd. fromfd or tofd can be set to AT_FDCWD in order to specify the current directory.

The rename() and renameat() functions return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

rename() and renameat() will fail and neither of the argument files will be affected if:

[]
A component of either path prefix denies search permission, or the requested link requires writing in a directory with a mode that denies write permission.
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from or to is the mount point for a mounted file system.
[]
The directory in which the entry for the new name is being placed cannot be extended because the user's quota of disk blocks on the file system containing the directory has been exhausted.
[]
from or to points outside the process's allocated address space.
[]
from is a parent directory of to, or an attempt is made to rename ‘.’ or ‘..’.
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An I/O error occurred while making or updating a directory entry.
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to is a directory, but from is not a directory.
[]
Too many symbolic links were encountered in translating either pathname.
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A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
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A component of the from path does not exist, or a path prefix of to does not exist.
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The directory in which the entry for the new name is being placed cannot be extended because there is no space left on the file system containing the directory.
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A component of either path prefix is not a directory, or from is a directory, but to is not a directory.
[]
to is a directory and is not empty.
[]
The directory containing from is marked sticky, and neither the containing directory nor from are owned by the effective user ID. Or the to file exists, the directory containing to is marked sticky, and neither the containing directory nor to are owned by the effective user ID.
[]
The requested link requires writing in a directory on a read-only file system.
[]
The link named by to and the file named by from are on different logical devices (file systems). Note that this error code will not be returned if the implementation permits cross-device links.

In addition, renameat() will fail if:

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from or to does not specify an absolute path and fromfd or tofd, respectively, is neither AT_FDCWD nor a valid file descriptor open for reading or searching.
[]
from or to is not an absolute path and fromfd or tofd, respectively, is a file descriptor associated with a non-directory file.

open(2), symlink(7)

The rename() function deviates from the semantics defined in IEEE Std 1003.1-1990 (“POSIX.1”), which specifies that if both from and to to the same existing file, rename() shall return successfully and performs no further action, whereas this implementation will remove the file specified by from unless both from and to are the same name in the same directory.

To retain conformance, a compatibility interface is provided by the POSIX Compatibility Library (libposix, -lposix) which is also be brought into scope if any of the _POSIX_SOURCE, _POSIX_C_SOURCE or _XOPEN_SOURCE preprocessor symbols are defined at compile-time: the rename() function conforms to IEEE Std 1003.1-1990 (“POSIX.1”) and X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”). renameat() conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

The system can deadlock if a loop in the file system graph is present. This loop takes the form of an entry in directory ‘a’, say ‘a/foo’, being a hard link to directory ‘b’, and an entry in directory ‘b’, say ‘b/bar’, being a hard link to directory ‘a’. When such a loop exists and two separate processes attempt to perform ‘rename a/foo b/bar’ and ‘rename b/bar a/foo’, respectively, the system may deadlock attempting to lock both directories for modification. Hard links to directories should be replaced by symbolic links by the system administrator.

February 14, 2025 NetBSD 11.0