wcpncpy(3)

💖 wcpncpy(3) 💖

okay bestie, so this is wcpncpy(3) from the Library Functions Manual — yes, the Library Functions Manual, the one we all know and love 🎀. sit down, grab a boba, and let me tell you about the wide-character girlboss who copies strings and then points you to the end of her work. no cap.

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✨ NAME ✨

wcpncpy — copy a fixed-size string of wide characters, returning a pointer to its end

like, she copies a fixed-size string of wide characters AND hands you back a pointer to the end. multitasking queen 👑

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📚 LIBRARY 📚

Standard C library (libc, -lc)

the classic. the original. the one that raised us 🫶

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🌈 SYNOPSIS 🌈

#include <wchar.h>

wchar_t *wcpncpy(size_t n;
                 wchar_t dest[restrict n],
                 const wchar_t *restrict src,
                 size_t n);

🧚 Feature Test Macro Requirements for glibc 🧚

(peep feature_test_macros(7) if u wanna know more, bestie)

wcpncpy():
    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _GNU_SOURCE

so if ur on glibc 2.10 or later u need _POSIX_C_SOURCE >= 200809L, and if ur on something older than glibc 2.10 u need _GNU_SOURCE. the way glibc keeps receipts of its own history... iconic honestly 💅

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💅 DESCRIPTION 💅

so wcpncpy() is literally the wide-character equivalent of the stpncpy(3) function. that's the whole vibe. she's the wide-char sister 🦋

she copies at most n wide characters from the wide-character string pointed to by src — including the terminating null wide (L'\0') — over to the array pointed to by dest. and exactly n wide characters get written at dest. exactly. she does not do half measures, bestie ✨

here's the tea tho:

• if the length wcslen(src) is smaller than n, the remaining wide characters in the array pointed to by dest are filled with L'\0' characters. padding queen 🎀
• if the length wcslen(src) is greater than or equal to n, the string pointed to by dest will not be L'\0' terminated. 😭 no null terminator. she just... stops. it's giving cliffhanger.

⚠️ okay this is important — the strings may not overlap. do not make them overlap. that's cursed behaviour territory, and not the fun kind of cursed 💀

⚠️ and also — the programmer must ensure that there is room for at least n wide characters at dest. that's on YOU, bestie. she is not checking. she is trusting u. do not betray her trust 🙈

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🔥 RETURN VALUE 🔥

wcpncpy() returns a pointer to one past the last non-null wide character written — that is:

dest + wcsnlen(src, n)

so she walks u to the finish line. main character exit 🚶♀️✨

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👑 ATTRIBUTES 👑

for an explanation of the terms used in this section, peep attributes(7). it's required reading, iykyk.

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

translation: MT-Safe means she's thread-safe, so multiple threads can hang out with her at the same time and nobody's gonna start drama 🔥

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⭐ STANDARDS ⭐

POSIX.1-2008.

certified. official. no notes. periodt 💅

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🌸 SEE ALSO 🌸

• stpncpy(3) — the narrow-char sibling
• wcsncpy(3) — the other wide-char cousin

go read those too, bestie, the family is adorable 🫶

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and that's the whole page!! 🦋💖 this little baby lives in Linux man-pages 6.20, dated 2026-02-08. love that for her. go forth and copy wide characters responsibly, and remember: exactly n or nothing at all ✨🎀💜