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RENAME(2) System Calls Manual RENAME(2)

rename, renameat — change the name of a file

#include <stdio.h>

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

#include <fcntl.h>
#include <stdio.h>

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

The () function 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 if to already exists, 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.

The () function is equivalent to rename() except that where from or to specifies a relative path, the directory entry names used are resolved relative to the directories associated with file descriptors fromfd or tofd (respectively) instead of the current working directory.

If () is passed the special value AT_FDCWD (defined in <fcntl.h>) in the fromfd or tofd parameter, the current working directory is used for resolving the respective from or to argument.

Upon successful completion, the value 0 is returned; 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:

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A component of a pathname exceeded NAME_MAX characters, or an entire pathname (including the terminating NUL) exceeded PATH_MAX bytes.
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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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A component of either path prefix denies search permission.
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The requested change requires writing in a directory that denies write permission.
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The from argument is a directory and denies write permission.
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The directory containing from is marked sticky, and neither the containing directory nor from are owned by the effective user ID.
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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.
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Too many symbolic links were encountered in translating either pathname.
The link count on the source file or destination directory is at the maximum. A rename cannot be completed under these conditions.
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A component of either path prefix is not a directory.
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from is a directory, but to is not a directory.
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to is a directory, but from is not a directory.
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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.
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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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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.
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An I/O error occurred while making or updating a directory entry.
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The requested link requires writing in a directory on a read-only file system.
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from or to points outside the process's allocated address space.
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from is a parent directory of to, or an attempt is made to rename ‘.’ or ‘..’.
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to is a directory and is not empty.

Additionally, renameat() will fail if:

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The from or to argument specifies a relative path and the fromfd or tofd argument, respectively, is neither AT_FDCWD nor a valid file descriptor.
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The from or to argument specifies a relative path and the fromfd or tofd argument, respectively, is a valid file descriptor but it does not reference a directory.
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The from or to argument specifies a relative path but search permission is denied for the directory which the fromfd or tofd file descriptor, respectively, references.

mv(1), open(2), symlink(7)

The rename() and renameat() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

The renameat() function appeared in OpenBSD 5.0.

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.

September 10, 2015 OpenBSD-7.6