getpagesize(2)

💖 getpagesize — bestie, what even IS a page 💖

okay so this is getpagesize(2) from the System Calls Manual, section 2, and honestly? it's a tiny little function with a lot of lore. let's get into it 🫶

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✨ NAME ✨

getpagesize — get memory page size

basically: it tells you how big a memory page is. that's it. that's the whole job. queen behavior honestly 👑

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📚 LIBRARY 📚

Standard C library (libc, -lc)

so you're linking against the classic. nothing exotic. 💅

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🌸 SYNOPSIS 🌸

#include <unistd.h>

int getpagesize(void);

no arguments, returns an int. she takes nothing and gives everything 😌

🎀 Feature Test Macro Requirements for glibc 🎀

(see feature_test_macros(7) for the full tea ☕)

getpagesize():

• Since glibc 2.20:
  • _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
• glibc 2.12 to glibc 2.19:
  • _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)
• Before glibc 2.12:
  • _BSD_SOURCE || _XOPEN_SOURCE >= 500

like… the macros changed over the years, that's just how glibc girlies are 💀 don't @ me, check which version you're on.

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🦋 DESCRIPTION 🦋

so getpagesize() returns the number of bytes in a memory page. and what's a "page", you ask? it's a fixed-length block — the unit used for memory allocation and for file mapping done by mmap(2). 🗺️

that's the whole vibe. pages are the little bricks, and this function tells you how big the bricks are.

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🌈 VERSIONS 🌈

okay this part is important, bestie, pay attention:

a user program should not hard-code a page size. not as a literal, and not using the PAGE_SIZE macro. why? because some architectures support multiple page sizes. 🚨

like imagine hardcoding a number and then running on a machine where that's just wrong. embarrassing. don't do it. 🙈

and here's a fun fact about why this page lives in section 2 instead of section 3: Alpha, SPARC, and SPARC64 all have an actual Linux system call getpagesize(). the other architectures do not — they use the ELF auxiliary vector instead. so it counts as a system call page. iykyk ✨

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👑 STANDARDS 👑

None.

that's it. no standards. nothing. she's free. she's ungoverned. iconic 🔥

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💜 HISTORY 💜

• 4.2BSD, SVr4, SUSv1.
• in SUSv2 the getpagesize() call was labeled LEGACY, and then it got removed in POSIX.1-2001. rip bestie 😭
• glibc 2.0 returned a constant even on architectures with multiple page sizes. (which, as we discussed above, is a whole problem. not great. 💀)

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🍓 SEE ALSO 🍓

• mmap(2)
• sysconf(3)

go read those if you wanna know more about pages and how to ask the system things politely 💖

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and that's the page, bestie!! this one came from Linux man-pages 6.20, dated 2026-02-08 — go off, documentation queens 👑✨ mwah 💅🦋🌸