PRISON_CHECK(9)

✨ PRISON_CHECK(9) ✨

okay so bestie, we're in the Kernel Developer's Manual section 9 today and the vibes are immaculate 💅 this one's a little function that does exactly one thing and does it slayfully: it tells you whether two credentials are living in the same jail or not. jail as in FreeBSD jail, not jail jail, don't be weird about it 🙈

🎀 NAME 🎀

prison_check — determine if two credentials belong to the same jail

like literally that's it, that's the whole job description, she's a one-trick pony and her trick is iconic 🦋

🌸 SYNOPSIS 🌸

#include <sys/jail.h>

int
prison_check(struct ucred *cred1, struct ucred *cred2);

💖 DESCRIPTION 💖

okay so here's the tea 🍓 — this function can be used to determine if the two credentials cred1 and cred2 belong to the same jail.

that's it. that's the function. she looks at two struct ucred * pointers, and she tells you if they're jail-mates or not. main character energy, zero drama, no cap 👑

🔥 RETURN VALUES 🔥

okay this is the part where you actually have to pay attention, bestie, because the return value is a lil quirky 😭

• ESRCH — returned if cred1 has been jailed, and cred1 and cred2 do not belong to the same jail. so like: one of them is in a jail, and the two of them aren't in the same one. that's the sad path 💀
• zero — in all other cases, prison_check() returns zero. yes, all of them. every single other combination. zero. that's your happy path 🫶

⚠️ read that again slowly: it's not a simple true/false. the error only fires when cred1 is jailed and the two aren't in the same jail. everything else — including cred1 not being jailed at all — is a zero. iykyk ✨

🦋 SEE ALSO 🦋

• jail(2)

and that's the whole page, bestie, you ate that 💖

this lil masterpiece comes from the Debian crew, dated December 11, 2003 — yeah she's an elder but she's still serving looks ✨ 🎀🌈👑