errseq_set(9)

💖 errseq_set(9) — like, the kernel API manual, but make it make sense ✨

Hey bestie!! So this is from the Kernel API Manual (yes, that manual, the big serious one) and today's main character is errseq_set. Buckle up, it's short but it eats. 🫶

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🌸 NAME 🌸

errseq_set — set a errseq_t for later reporting 💅

⭐ SYNOPSIS ⭐

errseq_t errseq_set (errseq_t *eseq , int err );

Like, that's the whole vibe. Two args, one return, no drama. 🎀

🦋 ARGUMENTS 🦋

• eseq — the errseq_t field that should be set. This is the lil guy getting the update, okay? 👑
• err — the error to set, and it must be between -1 and -MAX_ERRNO. Not negotiable, bestie, that's the range. 🚨

💜 DESCRIPTION 💜

okay so here's what happens: this function sets the error in eseq, and it increments the sequence counter if the last sequence was sampled at some point in the past. That's the whole trick. ✨

And the golden rule — any error set will always overwrite an existing error. No merging, no "but what about the old one", it's giving replace-and-move-on. 💅

🌈 RETURN 🌈

It hands back the previous value, which is primarily for debugging purposes. Like, cute for snooping, that's it. 🙈

⚠️ Do not use the return value as a previously sampled value in later calls — it will not have the SEEN flag set. For real, don't do it. 😭

🔥 SEE ALSO 🔥

Kernel file ./lib/errseq.c — that's where the magic lives, iykyk — plus errseq_sample(9), errseq_check(9), and errseq_check_and_advance(9). The whole friend group fr fr. 🧚

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And that's the page!! Shoutout to ./lib for the source and October 2026 for the date — slay, iconic, periodt. 💀🌸⭐