• Log in

• If !filesystem::is_regular_file(from) (either because the source file doesn't exist or because it is not a regular file), report an error.
• Otherwise, if the destination file does not exist,

• copies the contents and the attributes of the file to which from resolves to the file to which to resolves (symlinks are followed).

• Otherwise, if the destination file already exists,

• report an error if any of the following is true:

• to and from are the same as determined by filesystem::equivalent(from, to) ;
• to is not a regular file as determined by !filesystem::is_regular_file(to) ;
• none of the filesystem::copy_file control options are set in options.

• Otherwise, if copy_options::skip_existing is set in options, do nothing.
• Otherwise, if copy_options::overwrite_existing is set in options, copy the contents and the attributes of the file to which from resolves to the file to which to resolves.
• Otherwise, if copy_options::update_existing is set in options, only copy the file if from is newer than to, as defined by filesystem::last_write_time() .

#include <filesystem>
#include <fstream>
#include <iostream>
namespace fs = std::filesystem;
 
int main()
{
 fs::create_directory("sandbox");
 std::ofstream ("sandbox/file1.txt").put('a');
 
 fs::copy_file("sandbox/file1.txt", "sandbox/file2.txt");
 
 // now there are two files in sandbox:
 std::cout << "file1.txt holds: "
 << std::ifstream ("sandbox/file1.txt").rdbuf() << '\n';
 std::cout << "file2.txt holds: "
 << std::ifstream ("sandbox/file2.txt").rdbuf() << '\n';
 
 // fail to copy directory
 fs::create_directory("sandbox/abc");
 try
 {
 fs::copy_file("sandbox/abc", "sandbox/def");
 }
 catch (fs::filesystem_error& e)
 {
 std::cout << "Could not copy sandbox/abc: " << e.what() << '\n';
 }
 fs::remove_all("sandbox");
}

Possible output:

file1.txt holds: a
file2.txt holds: a
Could not copy sandbox/abc: copy_file: Is a directory: "sandbox/abc", "sandbox/def"