NAME

rename, renameat - rename file relative to directory file descriptor

SYNOPSIS

#include <stdio.h>

int rename(const char *old, const char *new);


[CX] int renameat(int oldfd, const char *old, int newfd,
       const char *new);

DESCRIPTION

For rename(): ^[CX]  The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

The rename() function shall change the name of a file. The old argument points to the pathname of the file to be renamed. The new argument points to the new pathname of the file. ^[CX]  If the new argument does not resolve to an existing directory entry for a file of type directory and the new argument contains at least one non- <slash> character and ends with one or more trailing <slash> characters after all symbolic links have been processed, rename() shall fail.

If either the old or new argument names a symbolic link, rename() shall operate on the symbolic link itself, and shall not resolve the last component of the argument. If the old argument and the new argument resolve to either the same existing directory entry or different directory entries for the same existing file, rename() shall return successfully and perform no other action.

If the old argument points to the pathname of a file that is not a directory, the new argument shall not point to the pathname of a directory. If the link named by the new argument exists, it shall be removed and old renamed to new. In this case, a link named new shall remain visible to other processes throughout the renaming operation and refer either to the file referred to by new or old before the operation began. Write access permission is required for both the directory containing old and the directory containing new.

If the old argument points to the pathname of a directory, the new argument shall not point to the pathname of a file that is not a directory. If the directory named by the new argument exists, it shall be removed and old renamed to new. In this case, a link named new shall exist throughout the renaming operation and shall refer either to the directory referred to by new or old before the operation began. If new names an existing directory, it shall be required to be an empty directory.

If either pathname argument refers to a path whose final component is either dot or dot-dot, rename() shall fail.

If the old argument points to a pathname of a symbolic link, the symbolic link shall be renamed. If the new argument points to a pathname of a symbolic link, the symbolic link shall be removed.

The old pathname shall not name an ancestor directory of the new pathname. Write access permission is required for the directory containing old and the directory containing new. If the old argument points to the pathname of a directory, write access permission may be required for the directory named by old, and, if it exists, the directory named by new.

If the link named by the new argument exists and the file's link count becomes 0 when it is removed and no process has the file open, the space occupied by the file shall be freed and the file shall no longer be accessible. If one or more processes have the file open when the last link is removed, the link shall be removed before rename() returns, but the removal of the file contents shall be postponed until all references to the file are closed.

Upon successful completion, rename() shall mark for update the last data modification and last file status change timestamps of the parent directory of each file.

If the rename() function fails for any reason other than [EIO], any file named by new shall be unaffected.

The renameat() function shall be equivalent to the rename() function except in the case where either old or new specifies a relative path. If old is a relative path, the file to be renamed is located relative to the directory associated with the file descriptor oldfd instead of the current working directory. If new is a relative path, the same happens only relative to the directory associated with newfd. If the file descriptor was opened without O_SEARCH, the function shall check whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the file descriptor was opened with O_SEARCH, the function shall not perform the check.

If renameat() is passed the special value AT_FDCWD in the oldfd or newfd parameter, the current working directory shall be used in the determination of the file for the respective path parameter.

RETURN VALUE

Upon successful completion, the rename() function shall return 0. Otherwise, it shall return -1, ^[CX] errno shall be set to indicate the error,  and neither the file named by old nor the file named by new shall be changed or created.

^[CX] Upon successful completion, the renameat() function shall return 0. Otherwise, it shall return -1 and set errno to indicate the error.

ERRORS

The rename() ^[CX]  and renameat()  functions shall fail if:

[EACCES]

^[CX] A component of either path prefix denies search permission; or one of the directories containing old or new denies write permissions; or, write permission is required and is denied for a directory pointed to by the old or new arguments.

[EBUSY]

^[CX] The directory named by old or new is currently in use by the system or another process, and the implementation considers this an error.

[EEXIST] or [ENOTEMPTY]

^[CX]
The link named by new is a directory that is not an empty directory.

[EINVAL]

^[CX] The old pathname names an ancestor directory of the new pathname, or either pathname argument contains a final component that is dot or dot-dot.

[EIO]

^[CX] A physical I/O error has occurred.

[EISDIR]

^[CX] The new argument points to a directory and the old argument points to a file that is not a directory.

[ELOOP]

^[CX] A loop exists in symbolic links encountered during resolution of the path argument.

[EMLINK]

^[CX] The file named by old is a directory, and the link count of the parent directory of new would exceed {LINK_MAX}.

[ENAMETOOLONG]

^[CX]
The length of a component of a pathname is longer than {NAME_MAX}.

[ENOENT]

^[CX] The link named by old does not name an existing file, a component of the path prefix of new does not exist, or either old or new points to an empty string.

[ENOSPC]

^[CX] The directory that would contain new cannot be extended.

[ENOTDIR]

^[CX] A component of either path prefix names an existing file that is neither a directory nor a symbolic link to a directory; or the old argument names a directory and the new argument names a non-directory file; or the old argument contains at least one non- <slash> character and ends with one or more trailing <slash> characters and the last pathname component names an existing file that is neither a directory nor a symbolic link to a directory; or the old argument names an existing non-directory file and the new argument names a nonexistent file, contains at least one non- <slash> character, and ends with one or more trailing <slash> characters; or the new argument names an existing non-directory file, contains at least one non- <slash> character, and ends with one or more trailing <slash> characters.

[EPERM] or [EACCES]

^[XSI]
The S_ISVTX flag is set on the directory containing the file referred to by old and the process does not satisfy the criteria specified in XBD Directory Protection with respect to old; or new refers to an existing file, the S_ISVTX flag is set on the directory containing this file, and the process does not satisfy the criteria specified in XBD Directory Protection with respect to this file.

[EROFS]

^[CX] The requested operation requires writing in a directory on a read-only file system.

[EXDEV]

^[CX] The links named by new and old are on different file systems and the implementation does not support links between file systems.

^[CX] In addition, the renameat() function shall fail if:

[EACCES]

oldfd or newfd was not opened with O_SEARCH and the permissions of the directory underlying oldfd or newfd respectively do not permit directory searches.

[EBADF]

The old argument does not specify an absolute path and the oldfd argument is neither AT_FDCWD nor a valid file descriptor open for reading or searching, or the new argument does not specify an absolute path and the newfd argument is neither AT_FDCWD nor a valid file descriptor open for reading or searching.

[ENOTDIR]

The old or new argument is not an absolute path and oldfd or newfd, respectively, is a file descriptor associated with a non-directory file.

The rename() ^[CX]  and renameat()  functions may fail if:

[EBUSY]

^{[OB XSR]} The file named by the old or new arguments is a named STREAM.

[ELOOP]

^[CX] More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.

[ENAMETOOLONG]

^[CX]
The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic link produced an intermediate result with a length that exceeds {PATH_MAX}.

[ETXTBSY]

^[CX] The file named by new exists and is the last directory entry to a pure procedure (shared text) file that is being executed.

EXAMPLES

Renaming a File

The following example shows how to rename a file named /home/cnd/mod1 to /home/cnd/mod2.

#include <stdio.h>


int status;
...
status = rename("/home/cnd/mod1", "/home/cnd/mod2");

APPLICATION USAGE

Some implementations mark for update the last file status change timestamp of renamed files and some do not. Applications which make use of the last file status change timestamp may behave differently with respect to renamed files unless they are designed to allow for either behavior.

RATIONALE

This rename() function is equivalent for regular files to that defined by the ISO C standard. Its inclusion here expands that definition to include actions on directories and specifies behavior when the new parameter names a file that already exists. That specification requires that the action of the function be atomic.

One of the reasons for introducing this function was to have a means of renaming directories while permitting implementations to prohibit the use of link() and unlink() with directories, thus constraining links to directories to those made by mkdir().

The specification that if old and new refer to the same file is intended to guarantee that:

rename("x", "x");

does not remove the file.

Renaming dot or dot-dot is prohibited in order to prevent cyclical file system paths.

See also the descriptions of [ENOTEMPTY] and [ENAMETOOLONG] in rmdir() and [EBUSY] in unlink(). For a discussion of [EXDEV], see link().

The purpose of the renameat() function is to rename files in directories other than the current working directory without exposure to race conditions. Any part of the path of a file could be changed in parallel to a call to rename(), resulting in unspecified behavior. By opening file descriptors for the source and target directories and using the renameat() function it can be guaranteed that that renamed file is located correctly and the resulting file is in the desired directory.

FUTURE DIRECTIONS

None.

SEE ALSO

link, rmdir, symlink, unlink

XBD Directory Protection, <stdio.h>

CHANGE HISTORY

First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.

Issue 5

The [EBUSY] error is added to the optional part of the ERRORS section.

Issue 6

Extensions beyond the ISO C standard are marked.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

• The [EIO] mandatory error condition is added.

• The [ELOOP] mandatory error condition is added.

• A second [ENAMETOOLONG] is added as an optional error condition.

• The [ETXTBSY] optional error condition is added.

The following changes were made to align with the IEEE P1003.1a draft standard:

• Details are added regarding the treatment of symbolic links.

• The [ELOOP] optional error condition is added.

The normative text is updated to avoid use of the term "must" for application requirements.

Issue 7

Austin Group Interpretation 1003.1-2001 #016 is applied, changing the definition of the [ENOTDIR] error.

Austin Group Interpretation 1003.1-2001 #076 is applied, clarifying the behavior if the final component of a path is either dot or dot-dot, and adding the associated [EINVAL] error case.

Austin Group Interpretation 1003.1-2001 #143 is applied.

Austin Group Interpretation 1003.1-2001 #145 is applied, clarifying that the [ENOENT] error condition also applies to the case in which a component of new does not exist.

Austin Group Interpretations 1003.1-2001 #174 and #181 are applied.

The renameat() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 2.

Changes are made related to support for finegrained timestamps.

Changes are made to allow a directory to be opened for searching.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0508 [324], XSH/TC1-2008/0509 [147], XSH/TC1-2008/0510 [379], XSH/TC1-2008/0511 [278], and XSH/TC1-2008/0512 [278] are applied.