wcsnlen(3)

🌸 wcsnlen(3) — aka "how long is this wide string, but make it ✨bounded✨"

okay bestie, welcome to the wcsnlen page, from the Library Functions Manual 💖

LIBRARY: Standard C library (libc, -lc) 🫶

---

✨ SYNOPSIS ✨

#include <wchar.h>

size_t wcsnlen(const wchar_t s[], size_t maxlen);

🎀 Feature Test Macro Requirements for glibc

(psst, go look at feature_test_macros(7) if you don't know what these are, iykyk)

wcsnlen():

• Since glibc 2.10:
  • _POSIX_C_SOURCE >= 200809L
• Before glibc 2.10:
  • _GNU_SOURCE

---

💜 DESCRIPTION

So like… wcsnlen() is literally the wide-character version of strnlen(3). That's the whole vibe. 👑

It gives you back the number of wide-characters in the string that s points at — and not counting the terminating null wide character (L'\0') — but it caps out at maxlen wide characters.

⚠️ not me stressing this enough: maxlen is not a byte count. it's wide characters, bestie. do not get it twisted. 💅

And while it's doing all that, wcsnlen() only ever peeks at the first maxlen wide characters at s, and it never looks past s[maxlen-1]. no overstepping, no scrolling past the boundary, respectful queen behavior fr fr. 🦋

---

🌈 RETURN VALUE

wcsnlen() hands you back wcslen(s) — but only if that's less than maxlen. Otherwise (aka if there's no null wide character hanging out among those first maxlen wide characters that s points to) it just returns maxlen. Simple. Iconic. No drama. ⭐

---

👑 ATTRIBUTES

For the whole explanation of what these terms even mean, go check attributes(7). 🧚

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

yes bestie, MT-Safe — she's safe to call from multiple threads, periodt. 💖

---

🍓 STANDARDS

POSIX.1-2008. ✨ certified, official, on the list.

---

🦋 HISTORY

glibc 2.1. she's been here since forever, a true elder of the game.

---

💫 SEE ALSO

• strnlen(3)
• wcslen(3)

---

okay that's the whole page!! go forth and count your wide characters responsibly, bestie 💅🌸

Linux man-pages 6.20 — dated 2026-02-08 🎀 mwah, love u, bye!! 💖