#include <stdio.h>
int rename(const char *old, const char *new);
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.
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 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 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 new pathname shall not contain a path prefix that names old. 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 st_ctime and st_mtime fields 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.
Upon successful completion, rename() shall return 0; otherwise, -1 shall be returned, 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.
The rename() function shall fail if:
The link named by new is a directory that is not an empty directory.
The length of the old or new argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.
The S_ISVTX flag is set on the directory containing the file referred to by old and the caller is not the file owner, nor is the caller the directory owner, nor does the caller have appropriate privileges; or new refers to an existing file, the S_ISVTX flag is set on the directory containing this file, and the caller is not the file owner, nor is the caller the directory owner, nor does the caller have appropriate privileges.
The rename() function may fail if:
As a result of encountering a symbolic link in resolution of the path argument, the length of the substituted pathname string exceeded {PATH_MAX}.
The following sections are informative.
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");
Some implementations mark for update the st_ctime field of renamed files and some do not. Applications which make use of the st_ctime field may behave differently with respect to renamed files unless they are designed to allow for either behavior.
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() .
link(), rmdir(), symlink(), unlink(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>