std::filesystem::path::make_preferred(3)

NAME
std::filesystem::path::make_preferred - std::filesystem::path::make_preferred

Synopsis
   path& make_preferred(); (since C++17)
   Converts all directory separators in the generic-format view of the path to the
   preferred directory separator.
   For example, on Windows, where \ is the preferred separator, the path foo/bar will
   be converted to foo\bar.

Parameters
   (none)

Return value
   *this

Exceptions
   May throw implementation-defined exceptions.

Example
   Windows can use / as a separator, but prefers \, so make_preferred converts the
   forward slashes to backslashes. On the other hand, POSIX does not use \ as a
   separator, because backslashes are valid filename characters — the Windows path on
   POSIX actually refers to a file with the name "a\\b\\c". For this reason the
   "separators" are not converted. // Run this code
 #include <filesystem>
 #include <iostream>
 int main()
 {
     std::filesystem::path
         windows_path("a\\b\\c"),
         posix_path("a/b/c");
     std::cout
         << "Windows path: "
         << windows_path << " -> "
         << windows_path.make_preferred() << '\n'
         << "POSIX path: "
         << posix_path << " -> "
         << posix_path.make_preferred() << '\n';
 }

Output:
 // on Windows
 Windows path: "a\\b\\c" -> "a\\b\\c"
 POSIX path: "a/b/c" -> "a\\b\\c"
 // on POSIX
 Windows path: "a\\b\\c" -> "a\\b\\c"
 POSIX path: "a/b/c" -> "a/b/c"

See also
                        alternative directory separator which may be used in addition
   constexpr value_type to the portable /. On Windows, this is the backslash character
   preferred_separator \. On POSIX, this is the same forward slash / as the portable
   [static] separator
                        (public static member constant)