31 Input/output library [input.output]

31.12 File systems [filesystems]

31.12.13 Filesystem operation functions [fs.op.funcs]

31.12.13.4 Copy [fs.op.copy]

void filesystem::copy(const path& from, const path& to);
Effects: Equivalent to copy(from, to, copy_options​::​none).
void filesystem::copy(const path& from, const path& to, error_code& ec);
Effects: Equivalent to copy(from, to, copy_options​::​none, ec).
void filesystem::copy(const path& from, const path& to, copy_options options); void filesystem::copy(const path& from, const path& to, copy_options options, error_code& ec);
Preconditions: At most one element from each option group ([fs.enum.copy.opts]) is set in options.
Effects: Before the first use of f and t:
  • If (options & copy_options::create_symlinks) != copy_options::none || (options & copy_options::skip_symlinks) != copy_options::none then auto f = symlink_status(from) and if needed auto t = symlink_status(to).
  • Otherwise, if (options & copy_options::copy_symlinks) != copy_options::none then auto f = symlink_status(from) and if needed auto t = status(to).
  • Otherwise, auto f = status(from) and if needed auto t = status(to).
Effects are then as follows:
  • If f.type() or t.type() is an implementation-defined file type ([fs.enum.file.type]), then the effects are implementation-defined.
  • Otherwise, an error is reported as specified in [fs.err.report] if
    • exists(f) is false, or
    • equivalent(from, to) is true, or
    • is_other(f) || is_other(t) is true, or
    • is_directory(f) && is_regular_file(t) is true.
  • Otherwise, if is_symlink(f), then:
    • If (options & copy_options​::​skip_symlinks) != copy_options​::​none then return.
    • Otherwise if !exists(t) && (options & copy_options::copy_symlinks) != copy_options::none then copy_symlink(from, to).
    • Otherwise report an error as specified in [fs.err.report].
  • Otherwise, if is_regular_file(f), then:
    • If (options & copy_options​::​directories_only) != copy_options​::​none, then return.
    • Otherwise, if (options & copy_options​::​create_symlinks) != copy_options​::​none, then create a symbolic link to the source file.
    • Otherwise, if (options & copy_options​::​create_hard_links) != copy_options​::​none, then create a hard link to the source file.
    • Otherwise, if is_directory(t), then copy_file(from, to/from.filename(), options).
    • Otherwise, copy_file(from, to, options).
  • Otherwise, if is_directory(f) && (options & copy_options::create_symlinks) != copy_options::none then report an error with an error_code argument equal to make_error_code(errc​::​is_a_directory).
  • Otherwise, if is_directory(f) && ((options & copy_options::recursive) != copy_options::none || options == copy_options::none) then:
    • If exists(t) is false, then create_directory(to, from).
    • Then, iterate over the files in from, as if by for (const directory_entry& x : directory_iterator(from)) copy(x.path(), to/x.path().filename(), options | copy_options::in-recursive-copy); where in-recursive-copy is a bitmask element of copy_options that is not one of the elements in [fs.enum.copy.opts].
  • Otherwise, for the signature with argument ec, ec.clear().
  • Otherwise, no effects.
Throws: As specified in [fs.err.report].
Remarks: For the signature with argument ec, any library functions called by the implementation shall have an error_code argument if applicable.
[Example 1: 
Given this directory structure:
/dir1
  file1
  file2
  dir2
    file3
Calling copy("/dir1", "/dir3") would result in:
/dir1
  file1
  file2
  dir2
    file3
/dir3
  file1
  file2
Alternatively, calling copy("/dir1", "/dir3", copy_options​::​recursive) would result in:
/dir1
  file1
  file2
  dir2
    file3
/dir3
  file1
  file2
  dir2
    file3
— end example]