std::filesy...::path::path(3)

💅 std::filesystem::path::path — the one and only

okay so this is std::filesystem::path::path(3), straight out of the C++ Standard Libary manual, and bestie, it's a lot — but it's literally just "how do I make a path object" and honestly? iconic. every single one of these is (since C++17), no cap. let's get into it 🌸

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✨ Synopsis ✨

eight overloads. eight. and yes you're gonna learn all of them 💖

path() noexcept;
(1) (since C++17)
   path( const path& p );
(2) (since C++17)
   path( path&& p ) noexcept;
(3) (since C++17)
   path( string_type&& source, format fmt = auto_format );
(4) (since C++17)
   template< class Source >
(5) (since C++17)
   path( const Source& source, format fmt = auto_format );
   template< class InputIt >
(6) (since C++17)
   path( InputIt first, InputIt last, format fmt = auto_format );
   template< class Source >
   path( const Source& source, const std::locale& loc, format fmt =
(7) (since C++17)
   auto_format );
   template< class InputIt >
   path( InputIt first, InputIt last, const std::locale& loc, format
(8) (since C++17)
   fmt = auto_format );

so what does this whole thing do? it constructs a new path object. that's the vibe 🦋

1. Constructs an empty path. blank. empty. nothing. a clean slate ✨
2. Copy constructor. Constructs a path whose pathname — in both native and generic formats — is the same as that of p. twin energy 👯
3. Move constructor. Constructs a path whose pathname, in both native and generic formats, is the same as that of p, and p is left in a valid but unspecified state. it's giving "no thoughts head empty" but like, legally 💀
4. 4–6) Constructs the path from a character sequence (format interpreted as specified by fmt) provided by source (4, 5), which is a pointer or an input iterator to a null-terminated character/wide character sequence, an std::basic_string or an std::basic_string_view, or represented as a pair of input iterators [first, last) (6). Any of the character types char, char8_t (since C++20), char16_t, char32_t, wchar_t is allowed, and the method of conversion to the native character set depends on the character type used by source. 🧚
   • If the source character type is char, the encoding of the source is assumed to be the native narrow encoding (so no conversion takes place on POSIX systems).
   • If the source character type is char8_t (since C++20), conversion from UTF-8 to native filesystem encoding is used.
   • If the source character type is char16_t, conversion from UTF-16 to native filesystem encoding is used.
   • If the source character type is char32_t, conversion from UTF-32 to native filesystem encoding is used.
   • If the source character type is wchar_t, the input is assumed to be the native wide encoding (so no conversion takes places on Windows). 🍓
5. 7, 8) Constructs the path from a character sequence (format interpreted as specified by fmt) provided by source (7), which is a pointer or an input iterator to a null-terminated character sequence, an std::string, an std::string_view, or represented as a pair of input iterators [first, last) (8). The only character type allowed is char. Uses loc to perform the character encoding conversion. If value_type is wchar_t, converts from to wide using the std::codecvt<wchar_t, char, std::mbstate_t> facet of loc. Otherwise, first converts to wide using the std::codecvt<wchar_t, char, std::mbstate_t> facet and then converts to filesystem native character type using std::codecvt<wchar_t,value_type> facet of loc. 😭 (yes that sentence is a marathon, i don't make the rules)

(5) and (7) participate in overload resolution only if Source and path are not the same type, and either: - Source is a specialization of std::basic_string or std::basic_string_view, or - std::iterator_traits<std::decay_t<Source>>::value_type is valid and denotes a possibly const-qualified encoding character type (char, char8_t (since C++20), char16_t, char32_t, or wchar_t).

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💜 Parameters 💜

• p — a path to copy
• source — std::basic_string, std::basic_string_view, pointer to a null-terminated character string, or input iterator with a character value type that points to a null-terminated character sequence (the character type must be char for overload (7))
• first, last — pair of LegacyInputIterators that specify a character sequence
• fmt — enumerator of type path::format which specifies how pathname format is to be interpreted
• loc — locale that defines encoding conversion to use

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🎀 Type requirements 🎀

• InputIt must meet the requirements of LegacyInputIterator.
• The value type of InputIt must be one of the character types char, wchar_t, char8_t (since C++20), char16_t and char32_t to use the overload (6).
• The value type of InputIt must be char to use the overload (8).

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🔥 Exceptions 🔥

2, 4–8) May throw implementation-defined exceptions. (not me warning you twice 💀)

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🌈 Notes 🌈

For portable pathname generation from Unicode strings, see u8path. (until C++20)

(since C++20) the path constructor supports creation from UTF-8 string when the source is a sequence of char8_t. slay ✨

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👑 Example 👑

// Run this code

#include <filesystem>
#include <iostream>
namespace fs = std::filesystem;

int main()
{
    fs::path p1 = "/usr/lib/sendmail.cf"; // portable format
    fs::path p2 = "C:\\users\\abcdef\\AppData\\Local\\Temp\\"; // native format
    fs::path p3 = U"D:/猫.txt"; // UTF-32 string
    fs::path p4 = u8"~/狗.txt"; // UTF-8 string

    std::cout << "p1 = " << p1 << '\n'
              << "p2 = " << p2 << '\n'
              << "p3 = " << p3 << '\n'
              << "p4 = " << p4 << '\n';
}

✨ Output ✨

p1 = "/usr/lib/sendmail.cf"
p2 = "C:\\users\\abcdef\\AppData\\Local\\Temp\\"
p3 = "D:/猫.txt"
p4 = "~/狗.txt"

look at those paths go 😭🫶 so clean.

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🦋 Defect reports 🦋

The following behavior-changing defect reports were applied retroactively to previously published C++ standards. (yes, they literally went back in time to fix stuff — main character energy 👑)

• LWG 3244 — applied to C++17 — behavior as published: constraint that Source cannot be path was missing → correct behavior: constraint that Source cannot be path was added ✅

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💫 See also 💫

• u8path — creates a path from a UTF-8 encoded source (C++17) (deprecated in C++20) (function)

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and that's the whole page, bestie — you ate that 🍓💅

source + version: http://cppreference.com, dated 2024.06.10 — go forth and construct paths, ily 💖