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

💅 std::filesystem::path::stem — the C++ Standard Library glow-up

okay so bestie, you clicked on std::filesy...::path::stem(3) from the C++ Standard Libary and honestly? iconic choice. this is the page that teaches you how to peel the extension off a filename and keep the good part. slay. 🎀

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✨ NAME ✨

std::filesystem::path::stem — literally just std::filesystem::path::stem, no cap, that's the whole name 🫶

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🌸 Synopsis 🌸

path stem() const;  (since C++17)

so here's the vibe: this bad boy returns the filename identified by the generic-format path stripped of its extension. that's it. that's the whole job. 💅

more specifically — and this is the part people always get wrong, so pay attention — it returns the substring from the beginning of filename() up to and not including the last period (.) character, with the following exceptions:

• 🦋 If the first character in the filename is a period, that period is ignored (a filename like ".profile" is not treated as an extension). so dotfiles keep their dot. we respect the dotfiles here.
• 🦋 If the filename is one of the special filesystem components dot or dot-dot, or if it has no periods, the function returns the entire filename(). no periods? no problem, you get everything back.

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🧚 Parameters 🧚

(none) — she takes nothing. she needs nothing. main character energy fr. ✨

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👑 Return value 👑

The stem of the filename identified by the path (i.e. the filename without the final extension). lowkey the most useful little string you'll ever grab. 🔥

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💀 Exceptions 💀

May throw implementation-defined exceptions. so like... it might be messy, and it's up to your implementation to tell you how. not me being vague, that's just what the page says 🙈

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🌈 Example 🌈

// Run this code

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

int main()
{
    for (const fs::path p : {"/foo/bar.txt", "/foo/.bar", "foo.bar.baz.tar"})
        std::cout << "path: " << p << ", stem: " << p.stem() << '\n';

    std::cout << '\n';

    for (fs::path p = "foo.bar.baz.tar"; !p.extension().empty(); p = p.stem())
        std::cout << "path: " << p << ", extension: " << p.extension() << '\n';
}

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⭐ Output ⭐

path: "/foo/bar.txt", stem: "bar"
path: "/foo/.bar", stem: ".bar"
path: "foo.bar.baz.tar", stem: "foo.bar.baz"

path: "foo.bar.baz.tar", extension: ".tar"
path: "foo.bar.baz", extension: ".baz"
path: "foo.bar", extension: ".bar"

look at that second loop bestie — it just keeps calling stem() on itself until extension() is empty, and you get to watch the extension peel off one layer at a time. it's giving onion. it's giving satisfying. obsessed. 🧅✨

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🫶 See also 🫶

• filename — returns the filename path component (public member function)
• extension — returns the file extension path component (public member function)

the little trio: filename() gives you the whole name, extension() gives you the tail, and stem() gives you everything but the tail. iykyk 💜

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real talk though: exceptions are implementation-defined, so don't come crying to me if your compiler has opinions. go read its docs. 🎀

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and that's the page, babe! brought to you by http://cppreference.com, dated 2024.06.10 — mwah, go write something slay 💅🌸🦋