std::filesystem::copy

void copy( const std::filesystem::path& from,
           const std::filesystem::path& to );
void copy( const std::filesystem::path& from,
           const std::filesystem::path& to,
           std::error_code& ec );

void copy( const std::filesystem::path& from,
           const std::filesystem::path& to,
           std::filesystem::copy_options options );
void copy( const std::filesystem::path& from,
           const std::filesystem::path& to,
           std::filesystem::copy_options options,
           std::error_code& ec );

Copies files and directories, with a variety of options.

The behavior is as follows:

• First, before doing anything else, obtains type and permissions of from by no more than a single call to
• std::filesystem::symlink_status, if copy_options::skip_symlinks, copy_options::copy_symlinks, or copy_options::create_symlinks is present in options;
• std::filesystem::status otherwise.
• If necessary, obtains the status of to, by no more than a single call to
• std::filesystem::symlink_status, if copy_options::skip_symlinks or copy_options::create_symlinks is present in options;
• std::filesystem::status otherwise (including the case where copy_options::copy_symlinks is present in options).
• If from does not exist, reports an error.
• If from and to are the same file as determined by std::filesystem::equivalent, reports an error
• If either from or to is not a regular file, a directory, or a symlink, as determined by std::filesystem::is_other, reports an error
• If from is a directory, but to is a regular file, reports an error
• If from is a symbolic link, then
• If copy_options::skip_symlink is present in options, does nothing.
• Otherwise, if to does not exist and copy_options::copy_symlinks is present in options, then behaves as if copy_symlink(from, to)
• Otherwise, reports an error
• Otherwise, if from is a regular file, then
• If copy_options::directories_only is present in options, does nothing
• Otherwise, if copy_options::create_symlinks is present in options, creates a symlink to to. Note: from must be an absolute path unless to is in the current directory.
• Otherwise, if copy_options::create_hard_links is present in options, creates a hard link to to
• Otherwise, if to is a directory, then behaves as if copy_file(from, to/from.filename(), options) (creates a copy of from as a file in the directory to)
• Otherwise, behaves as if copy_file(from, to, options) (copies the file)
• Otherwise, if from is a directory and either options has copy_options::recursive or is copy_options::none,
• If to does not exist, first executes create_directory(to, from) (creates the new directory with a copy of the old directory's attributes)
• Then, whether to already existed or was just created, iterates over the files contained in from as if by for (const std::filesystem::directory_entry& x : std::filesystem::directory_iterator(from)) and for each directory entry, recursively calls copy(x.path(), to/x.path().filename(), options | unspecified), where unspecified is some unspecified set of copy options.
• Otherwise does nothing

Parameters

Return value

(none).

Exceptions

Notes

The default behavior when copying directories is the non-recursive copy: the files are copied, but not the subdirectories:

// Given
// /dir1 contains /dir1/file1, /dir1/file2, /dir1/dir2
// and /dir1/dir2 contains /dir1/dir2/file3
// After
std::filesystem::copy("/dir1", "/dir3");
// /dir3 is created (with the attributes of /dir1)
// /dir1/file1 is copied to /dir3/file1
// /dir1/file2 is copied to /dir3/file2

While with copy_options::recursive, the subdirectories are also copied, with their content, recursively.

// ...but after
std::filesystem::copy("/dir1", "/dir3", std::filesystem::copy_options::recursive);
// /dir3 is created (with the attributes of /dir1)
// /dir1/file1 is copied to /dir3/file1
// /dir1/file2 is copied to /dir3/file2
// /dir3/dir2 is created (with the attributes of /dir1/dir2)
// /dir1/dir2/file3 is copied to /dir3/dir2/file3

Example

#include <iostream>
#include <fstream>
#include <filesystem>
namespace fs = std::filesystem;
 
int main()
{
    fs::create_directories("sandbox/dir/subdir");
    std::ofstream("sandbox/file1.txt").put('a');
    fs::copy("sandbox/file1.txt", "sandbox/file2.txt"); // copy file
    fs::copy("sandbox/dir", "sandbox/dir2"); // copy directory (non-recursive)
    // sandbox holds 2 files and 2 directories, one of which has a subdirectory
    // sandbox/file1.txt
    // sandbox/file2.txt
    // sandbox/dir2
    // sandbox/dir
    //    sandbox/dir/subdir
    fs::copy("sandbox", "sandbox/copy", fs::copy_options::recursive);
    // sandbox/copy holds copies of the above files and subdirectories
    fs::remove_all("sandbox");
}

See also