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std::filesystem::path::make_preferred

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.

#include <filesystem>
#include <iostream>
#include <iomanip>
 
int main()
{
  std::filesystem::path windows_path{"a\\b\\c"};
  std::filesystem::path posix_path{"a/b/c"};
  std::cout << "Windows path: " 
            << std::quoted(windows_path.string()) << " -> " 
            << std::quoted(windows_path.make_preferred().string()) << '\n'
            << "POSIX path: "
            << std::quoted(posix_path.string()) << " -> " 
            << std::quoted(posix_path.make_preferred().string()) << '\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

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

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