__ffs(9)

💅 NAME 💅

okay so this is __ffs — the kernel API manual page for it, bestie — and it does exactly one thing: find the first bit in a word. that's it. that's the whole vibe. ✨

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✨ SYNOPSIS ✨

unsigned int __ffs (unsigned long word );

like literally that's the entire signature, copy it exactly please, no freestyling 🙈

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🎀 ARGUMENTS 🎀

• word — the word you wanna search. that's the one. the word. the thing you're hunting through for that first lil bit 🦋

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🦋 DESCRIPTION 🦋

so you hand it a word and it goes looking for the first bit. cute, simple, main character energy.

but — and this is the part where you gotta listen to me, fr fr — the behaviour is undefined if no bit exists. like, not "returns 0", not "returns -1", undefined. 😭 so your code should check against 0 first before you even think about calling this. do the vibe check on zero. periodt. 💀

⚠️ no cap: no bit in the word = undefined behaviour. check against 0 first, always, i'm begging 🫶

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🌸 SEE ALSO 🌸

• Kernel file ./tools/include/asm-generic/bitops/__ffs.h — go read the source, iykyk 👑

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okay that's the whole page, you ate it, i'm obsessed 💖 and just so we're cute and complete: this came from the source file ./tools/include/asm-generic/bi... and the date on it is October 2026 — so yeah, __ffs(9), fresh off the kernel API manual, slay 🌈👑🎀