PR_SET_KEEPCAPS(2const)

💖 PR_SET_KEEPCAPS 💖

okay bestie, so this is a <pink>2const</pink> page — aka a little slice of the prctl(2) universe, not a whole syscall of its own. It lives under the manual name PR_SET_KEEPCAPS, and honestly? It's giving "one job, does it well." 🎀

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✨ NAME ✨

PR_SET_KEEPCAPS — set the state of the "keep capabilities" flag 💅

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📚 LIBRARY 📚

Standard C library (libc, -lc) 🫶

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🌸 SYNOPSIS 🌸

#include <linux/prctl.h>  /* Definition of PR_* constants */
#include <sys/prctl.h>

int prctl(PR_SET_KEEPCAPS, long state);

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🦋 DESCRIPTION 🦋

So what are we actually doing here? You're setting the state of the calling thread's "keep capabilities" flag. That's the flag, yes, that specific one. 🙈

The whole effect of this flag? That's not explained here, bestie — it lives over in capabilities(7), so go read that if you want the lore. 📖✨

And state? It has to be exactly one of these two, no in-between, no vibes-based middle ground:

• 0L — clear the flag 🚫
• 1L — set the flag ✅

Heads up fr fr: the "keep capabilities" value gets reset to 0 on subsequent calls to execve(2). Every single time. No cap. So don't expect it to just linger around like a situationship. 💀

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🔥 RETURN VALUE 🔥

• On success, 0 is returned. slay. 👑
• On error, -1 is returned, and errno is set to indicate the error. 😭

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💀 ERRORS 💀

• EINVAL — state is not a valid value. Like, it wasn't 0L and it wasn't 1L. Pick a lane, bestie. 🙈
• EPERM — The caller's SECBIT_KEEP_CAPS_LOCKED flag is set (see capabilities(7)). You're locked out, the door is bolted, respectfully, no. 🚪🔒

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⭐ STANDARDS ⭐

Linux. Just Linux. That's the whole vibe. 🐧

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🕰️ HISTORY 🕰️

Linux 2.2.18 — a true elder, been iconic since day one. 💜

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🌈 SEE ALSO 🌈

• prctl(2)
• PR_GET_KEEPCAPS(2const)

(yes, the getter exists. they're a matching set. iykyk 🫶)

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okay that's the whole page!! mwah 💋 this one came from Linux man-pages 6.20, dated 2026-02-08, and it was PR_SET_KEEPCAPS(2const) the entire time. go keep some capabilities (or don't!) — either way, you ate. ✨💅🎀