ptrdiff_t(3type)

💖 ptrdiff_t(3type) — the whole vibe 💖

okay bestie, welcome to <ptrdiff_t>'s page, it lives in section 3type (that's the "here's a typedef, let me explain it" section, iykyk) and honestly? it's giving essential.

✨ NAME ✨

ptrdiff_t — count of elements or array index

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📚 LIBRARY 📚

Standard C library (libc) 🫶

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🌸 SYNOPSIS 🌸

#include <stddef.h>

typedef /* ... */  ptrdiff_t;

like. that's it. that's the whole declaration. typedef /* ... */ bestie, the real guts are up to your implementation 🙈

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🦋 DESCRIPTION 🦋

So what IS this queen? <pink>Used for a count of elements, or an array index.</pink> That's her whole job description 💅

She's also <cyan>the result of subtracting two pointers</cyan> — like, literally, subtract one pointer from another and boom, you get a ptrdiff_t (the name is not subtle, it's giving "pointer difference").

And the important part, no cap: <hotpink>it is a signed integer type capable of storing values in the range [PTRDIFF_MIN, PTRDIFF_MAX]</hotpink>. SIGNED. Which means she can go negative. Which means your pointer math can go negative. Which is exactly why she exists and why size_t can't do her job 👑

✨ the printf/scanf tea ✨

The length modifier for ptrdiff_t for the printf(3) and the scanf(3) families of functions is t, resulting commonly in %td or %ti for printing ptrdiff_t values. So next time you're printing one, don't be out here using %d like a menace — use %td or %ti 🎀

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👑 STANDARDS 👑

C11, POSIX.1-2024.

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🌈 HISTORY 🌈

C89, SUSv1, POSIX.1-2001.

she's been iconic since forever, fr fr 💀✨

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🎀 SEE ALSO 🎀

• size_t(3type) — her unsigned bestie, go say hi 🥰

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lowkey the cutest little typedef in <stddef.h>, tbh 🦋

this page came to you courtesy of Linux man-pages 6.20, dated 2026-02-08 💖 stay signed, bestie, and may all your pointer differences fit in range 🫶⭐