id_t(3type)

✨ id_t(3type) ✨

okay so bestie, welcome to id_t(3type) 💖 this is the little page about all the "who even are you" types — the ones that hold every ID the kernel ever asks about. no cap, it's foundational.

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🎀 NAME 🎀

pid_t, uid_t, gid_t, id_t — process/user/group identifier 💅

📚 LIBRARY 📚

Standard C library (libc) 🫶

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✨ SYNOPSIS ✨

#include <sys/types.h>

typedef /* ... */ pid_t;
typedef /* ... */ uid_t;
typedef /* ... */ gid_t;
typedef /* ... */ id_t;

yes bestie, that's literally all you need — one include and boom, four types 💖 (the /* ... */ is real, the actual underlying type is left as a mystery on purpose, so don't come for me)

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💜 DESCRIPTION 💜

• pid_t — this one holds process IDs, process group IDs, and session IDs. it's a signed integer type, so it's giving "I can go negative if I'm feeling spicy" ✨
• uid_t — the type that carries user IDs. it's an integer type, periodt 🌸
• gid_t — the type that carries group IDs. also an integer type 🎀
• id_t — the main character of this page 👑 it's a general identifier type. it's an integer type, and it's wide/loose enough to hold a pid_t, a uid_t, or a gid_t inside it. it's giving "one type to rule them all" 🦋

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🌈 STANDARDS 🌈

POSIX.1-2024. 💅

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🕰️ HISTORY 🕰️

• pid_t
• uid_t
• gid_t

→ all three: POSIX.1-1988. the OGs fr fr 🌸

• id_t → SUSv1, POSIX.1-2001 XSI, POSIX.1-2008. it arrived later and lowkey ate ✨

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📝 NOTES 📝

y'all — the tea is that <sys/types.h> is not the only place these types show up. lots of other headers also hand them to you, so here's the full receipts list 🧾

pid_t also comes from these besties:

<fcntl.h>, <sched.h>, <signal.h>, <spawn.h>, <sys/msg.h>, <sys/sem.h>, <sys/shm.h>, <sys/wait.h>, <termios.h>, <time.h>, <unistd.h>, and <utmpx.h>.

uid_t also comes from:

<pwd.h>, <signal.h>, <stropts.h>, <sys/ipc.h>, <sys/stat.h>, and <unistd.h>.

gid_t also comes from:

<grp.h>, <pwd.h>, <signal.h>, <stropts.h>, <sys/ipc.h>, <sys/stat.h>, and <unistd.h>.

and id_t also comes from:

<sys/resource.h>.

ok so quick vibe check: <sys/resource.h> is the only extra one for id_t, while pid_t has a whole squad. iconic behavior honestly 💀

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👀 SEE ALSO 👀

chown(2), fork(2), getegid(2), geteuid(2), getgid(2), getgroups(2), getpgid(2), getpid(2), getppid(2), getpriority(2), getpwnam(3), getresgid(2), getresuid(2), getsid(2), gettid(2), getuid(2), kill(2), pidfd_open(2), sched_setscheduler(2), waitid(2), getgrnam(3), sigqueue(3), credentials(7)

go read credentials(7) if you wanna understand the whole permissions vibe iykyk 🔥

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🏁 and that's the page bestie!! this one's from Linux man-pages 6.20, dated 2026-02-08 💖 now go forth and getpid() responsibly, ily, bye!! ✨💅🫶