# std::experimental::filesystem::rename

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< cpp‎ | experimental‎ | fs

Defined in header `<experimental/filesystem>` |  |
void rename( const path& old_p, const path& new_p ); void rename( const path& old_p, const path& new_p, std::error_code& ec ); |  | (filesystem TS)

Moves or renames the filesystem object identified by old_p to new_p as if by the POSIX rename:

- If old_p is a non-directory file, then new_p must be one of:

  - the same file as old_p or a hardlink to it: nothing is done in this case.
  - existing non-directory file: new_p is first deleted, then, without allowing other processes to observe new_p as deleted, the pathname new_p is linked to the file and old_p is unlinked from the file. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.
  - non-existing file in an existing directory: The pathname new_p is linked to the file and old_p is unlinked from the file. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.

- If old_p is a directory, then new_p must be one of:

  - the same directory as old_p or a hardlink to it: nothing is done in this case.
  - existing directory: new_p is deleted if empty on POSIX systems, but this may be an error on other systems. If not an error, then new_p is first deleted, then, without allowing other processes to observe new_p as deleted, the pathname new_p is linked to the directory and old_p is unlinked from the directory. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.
  - non-existing directory, not ending with a directory separator, and whose parent directory exists: The pathname new_p is linked to the directory and old_p is unlinked from the directory. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.

- Symlinks are not followed: if old_p is a symlink, it is itself renamed, not its target. If new_p is an existing symlink, it is itself erased, not its target.

Rename fails if

- new_p ends with dot or with dot-dot.
- new_p names a non-existing directory ending with a directory separator.
- old_p is a directory which is an ancestor of new_p.

### Parameters

old_p | - | path to move or rename
new_p | - | target path for the move/rename operation
ec | - | out-parameter for error reporting in the non-throwing overload

### Return value

(none)

### Exceptions

The overload that does not take a `error_code&` parameter throws filesystem_error on underlying OS API errors, constructed with `old_p` as the first argument, `new_p` as the second argument, and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails. The overload taking a `error_code&` parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. This overload has
`noexcept` specification:
noexcept

### Example

Run this code

    #include <experimental/filesystem>
    #include <fstream>
    #include <iostream>
    namespace fs = std::experimental::filesystem;

    int main()
    {
        fs::path p = fs::current_path() / "sandbox";
        fs::create_directories(p/"from");
        std::ofstream(p/"from/file1.txt").put('a');
        fs::create_directory(p/"to");

    //  fs::rename(p/"from/file1.txt", p/"to/"); // error: to is a directory
        fs::rename(p/"from/file1.txt", p/"to/file2.txt"); // OK
    //  fs::rename(p/"from", p/"to"); // error: to is not empty
        fs::rename(p/"from", p/"to/subdir"); // OK

        fs::remove_all(p);
    }

### See also

rename | renames a file (function)
remove remove_all | removes a file or empty directory removes a file or directory and all its contents, recursively (function)

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