std::filesystem::rename(3)

NAME
std::filesystem::rename - std::filesystem::rename

Synopsis
   Defined in header <filesystem>
   void rename( const std::filesystem::path& old_p, (1) (since C++17)
                const std::filesystem::path& new_p );
   void rename( const std::filesystem::path& old_p,
                const std::filesystem::path& new_p, (2) (since C++17)
                std::error_code& ec ) noexcept;
   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
   Any overload not marked noexcept may throw std::bad_alloc if memory allocation
   fails.
   1) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed
   with old_p as the first path argument, new_p as the second path argument, and the OS
   error code as the error code argument.
   2) Sets a std::error_code& parameter to the OS API error code if an OS API call
   fails, and executes ec.clear() if no errors occur.

Example
// Run this code
 #include <filesystem>
 #include <fstream>
 namespace fs = std::filesystem;
 int main()
 {
     std::filesystem::path p = std::filesystem::current_path() / "sandbox";
     std::filesystem::create_directories(p / "from");
     std::ofstream{ p / "from/file1.txt" }.put('a');
     std::filesystem::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
     std::filesystem::remove_all(p);
 }

See also
   rename renames a file
              (function)
   remove removes a file or empty directory
   remove_all removes a file or directory and all its contents, recursively
   (C++17) (function)
   (C++17)