sched_getcpu(3)

💅 NAME 💅

sched_getcpu — bestie, this literally tells you which CPU your calling thread is running on right now. Like a "where am I" but for silicon. ✨

📚 LIBRARY 📚

Standard C library (libc, -lc). Miss thing lives in libc, so you already know her.

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🎀 SYNOPSIS 🎀

#include <sched.h>

int sched_getcpu(void);

🦋 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

_sched_getcpu():

• Since glibc 2.14: _GNU_SOURCE
• Before glibc 2.14:

_BSD_SOURCE || _SVID_SOURCE
    /* _GNU_SOURCE also suffices */

okay so yes, you have to define the right macro or glibc will simply not let you in the group chat. that's just how it is 🫶

🌸 DESCRIPTION 🌸

sched_getcpu() returns the number of the CPU on which the calling thread is currently executing.

that's it. that's the whole function. it's giving "one job and she ate" 👑

⭐ RETURN VALUE ⭐

• On success: a nonnegative CPU number. slay, you found out where you live. 🌈
• On error: -1 is returned and errno is set to indicate the error. 😭

💀 ERRORS 💀

• ENOSYS — this kernel does not implement getcpu(2). bestie the kernel said no, and honestly? rude.

🔥 ATTRIBUTES 🔥

For an explanation of the terms used in this section, see attributes(7).

• Interface: sched_getcpu()
• Attribute: Thread safety
• Value: MT-Safe

MT-Safe means multiple threads can call her at the same time with zero drama. iconic behavior, no notes. 🎀

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👑 STANDARDS 👑

GNU. we're doing GNU things. periodt.

🧚 HISTORY 🧚

glibc 2.6. so she's been here since 2007, aging like fine wine, lowkey a legend.

🍓 NOTES 🍓

okay so the call

cpu = sched_getcpu();

is equivalent to the following getcpu(2) call:

int c, s;
s = getcpu(&c, NULL);
cpu = (s == -1) ? s : c;

literally the same vibe, just a glow-up wrapper. iykyk 💜

🌟 SEE ALSO 🌟

• getcpu(2)
• sched(7)

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that's the whole page bestie, go forth and know which CPU loves you back 💖

Linux man-pages 6.20, dated 2025-05-17 — mwah, that's the source and the date, sign-off done, no cap 🫶✨