std::experi...em_complete(3)

Okay bestie, welcome to the std::experi...em_complete(3) page from the C++ Standard Libary manual 💖 (yes, that manual name is staying exactly as it is).

💅 NAME 💅

std::experimental::filesystem::absolute, std::experimental::filesystem::system_complete — that’s the duo, and the page is literally named std::experimental::filesystem::absolute,std::experimental::filesystem::system_complete (the comma is doing its thing, no cap).

🌸 Synopsis 🌸

Defined in header <experimental/filesystem>. Both overloads are (filesystem TS), bestie.

Defined in header <experimental/filesystem>
path absolute( const path& p, const path& base = current_path()  (1)
(filesystem TS)
);
path system_complete( const path& p );                           (2)
(filesystem TS)
path system_complete( const path& p, error_code& ec );

1. absolute (1) — returns the absolute path of p relative to base, according to these rules:
   • If p has both root name and root directory (like "C:\users"), the path is returned, unmodified.
   • If p has a root name not followed by a root directory (like "C:text.txt"), then base is inserted between p’s root name and the remainder of p. Formally, p.root_name() / fs::absolute(base).root_directory() / fs::absolute(base).relative_path() / p.relative_path() is returned.
   • If p has no root name but has a root directory (like "/var/tmp/file.txt" on a POSIX system or "\users\ABC\Document.doc" on Windows), then the root name of base, if it has one, is prepended to p. On a POSIX system, p is not modified; on a Windows system, "\users\ABC\Document.doc" becomes "C:\users\ABC\Document.doc". Formally, fs::absolute(base).root_name() / p is returned.
   • If p has no root name and no root directory (like "../file.txt"), then the entire base is prepended to p. Formally, absolute(base) / p is returned.
2. system_complete (2) — obtains the absolute path that identifies the file that the OS file opening API would access given the pathname p. On POSIX systems, this is equivalent to (1) with the default base (fs::current_path()). On Windows systems, each logical drive has its own current working directory, and so if p is not already absolute and has a root name component (like "E:filename.txt"), that drive’s current working directory is used, which may have been set by an earlier executed program.

💖 Parameters 💖

• p — path to convert to absolute form.
• base — path (not necessarily absolute) to serve as the starting location.
• ec — out-parameter for error reporting in the non-throwing overload.

🦋 Return value 🦋

Returns an absolute (although not necessarily canonical) path formed by combining p and base as described above.

😭 Exceptions 😭

The overload that does not take an error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p as the first argument, base as the second argument, and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails.

The overload taking an error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. This overload has noexcept specification:

noexcept

👑 Notes 👑

On systems that support root names (e.g. Windows), the result of calling absolute on a relative path that has a root name (e.g. "D:file.txt" when the root name of base is different) will usually result in a non-existent path.

🔥 Example 🔥

// Run this code

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

int main()
{
    fs::path p = "C:cl.exe";
    std::cout << "Current path is " << fs::current_path() << '\n'
              << "Absolute path for " << p << " is " << fs::absolute(p)
       << '\n'
              << "System complete path for " << p << " is "
              << fs::system_complete(p) << '\n';
}

🌈 Possible output 🌈

Current path is "D:/local/ConsoleApplication1"
Absolute path for "C:cl.exe" is "C:/local/ConsoleApplication1/cl.exe"
System complete path for "C:cl.exe" is "C:\Program Files
       (x86)\Microsoft Visual Studio 12.0\VC\bin\cl.exe"

💜 See also 💜

• canonical — composes a canonical path (function).

🎀 Categories 🎀

• Noindexed pages
• unconditionally noexcept

🙈 Hidden categories 🙈

• Pages with unreviewed unconditional noexcept template
• Pages with unreviewed noexcept template

💖 Cute little sign-off: this page is from http://cppreference.com, version/date 2024.06.10, and its title is std::experi...em_complete(3). Bye bestie, go make those paths absolute! 🎀✨