std::filesystem::rename

void rename( const std::filesystem::path& old_p,
             const std::filesystem::path& new_p );
void rename( const std::filesystem::path& old_p,
             const std::filesystem::path& new_p,
             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

Return value

(none).

Exceptions

The overload that does not take a std::error_code& parameter throws 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. The overload taking a std::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. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

Example

#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