strlen(3)

💖 strlen(3) — string length, but make it cute 💖

okay so bestie, welcome to the glow-up of strlen(3) from the Library Functions Manual. yes we're doing libc today and yes you're gonna understand it. periodt.

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✨ NAME ✨

strlen — string length. that's it, that's the whole vibe. it counts. 💅

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📚 LIBRARY 📚

Standard C library (libc, -lc). the classic. the blueprint. the one you already linked without thinking about it. 🫶

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🌸 SYNOPSIS 🌸

#include <string.h>

size_t strlen(const char *s);

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🦋 DESCRIPTION 🦋

so like. strlen() calculates the length of the string pointed to by s, and the way that it does that is by excluding the terminating null byte ('\0'). that last part is the whole entire plot twist, bestie. the '\0' is the vibe-ruiner of the byte count. it does not get included. it does not get counted. it stays outside. 😌

it's equivalent to this, no cap:

strnul(s) - s

like it's literally just pointer maths wearing a cute little outfit. pointer to the null minus pointer to the start. iconic behaviour honestly.

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🎀 RETURN VALUE 🎀

strlen() returns the number of bytes in the string pointed to by s. bytes, not characters, not graphemes, not feelings. bytes. ✨

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💜 ATTRIBUTES 💜

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

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

yes bestie, MT-Safe. she's safe to call from multiple threads at once. multithreaded main character energy. 👑

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🌈 STANDARDS 🌈

C11, POSIX.1-2008.

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⭐ HISTORY ⭐

POSIX.1-2001, C89, SVr4, 4.3BSD. she's been around. she's seen things. she's still the moment. 💀✨

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👑 SEE ALSO 👑

• string(3)
• strnul(3)
• wcslen(3)

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fr fr, the only thing you have to remember: no null byte in the count. that's the whole tea. 🍓

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that's the page, bestie!! this one shipped as part of Linux man-pages 6.20, dated 2026-08-10, and honestly? she ate. mwah. 💖🎀🦋🧚‍♀️