December 27, 2005 RENAME 2

### NAME

rename - change the name of a file

### LIBRARY

Standard C Library (libc, -lc)

### SYNOPSIS

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

### DESCRIPTION

rename(``) 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.

rename(``) 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` are pathnames of the same existing file in the file system's name space, rename(``) returns successfully and performs no other action.

### RETURN VALUES

A 0 value is returned if the operation succeeds, otherwise rename(``) returns -1 and the global variable errno indicates the reason for the failure.

### ERRORS

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

[```ENAMETOOLONG`]
  A component of a pathname exceeded ```{NAME_MAX}` characters, or an entire path name exceeded ```{PATH_MAX}` characters.

[```ENOENT`]
  A component of the ```from` path does not exist, or a path prefix of ```to` does not exist.

[```EACCES`]
  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.

[```EPERM`]
  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.

[```ELOOP`]
  Too many symbolic links were encountered in translating either pathname.

[```ENOTDIR`]
  A component of either path prefix is not a directory, or ```from` is a directory, but ```to` is not a directory.

[```EISDIR`]
  ```to` is a directory, but ```from` is not a directory.

[```EXDEV`]
  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.

[```ENOSPC`]
  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.

[```EDQUOT`]
  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.

[```EIO`]
  An I/O error occurred while making or updating a directory entry.

[```EROFS`]
  The requested link requires writing in a directory on a read-only file system.

[```EFAULT`]
  Path points outside the process's allocated address space.

[```EINVAL`]
  ```from` is a parent directory of ```to`, or an attempt is made to rename `.' or `..'.

[```ENOTEMPTY`]
  ```to` is a directory and is not empty.

[```EBUSY`]
  ```from` or ```to` is the mount point for a mounted file system.

### SEE ALSO

open(2), symlink(7)

### STANDARDS

The rename(``) function deviates from the semantics defined in ISO/IEC 9945-1:1990 (``POSIX.1'') , which specifies that if both ```from` and ```to` link 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 pathnames of the same file in the file system's name space.

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 ISO/IEC 9945-1:1990 (``POSIX.1'') and X/Open Portability Guide Issue 4, Version 2 (``XPG4.2'') .

### BUGS

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.