vscnprintf(9)

💅 vscnprintf(9) — or, "how to format a string into a buffer, the va_list way" 🎀

okay so real talk, this is a page from the Kernel API Manual and honestly? she's a little niche but she serves. if you're already holding a va_list and you need to slam a formatted string into a buffer without yeeting past the end, bestie, this is literally your girl. ✨

---

✨ SYNOPSIS ✨

int vscnprintf (char *buf , size_t size , const char *fmt , va_list args
);

---

🫶 ARGUMENTS 🫶

• buf — the buffer where the result is gonna live. it's giving "put the string here please." ✨
• size — how big the buffer is, and yes that count includes the trailing null space. don't forget the null, i'm begging 😭
• fmt — the format string you're using. the blueprint. the vibe setter. 💅
• args — the arguments for that format string. the whole reason you're here. 🎀

---

🌸 DESCRIPTION 🌸

okay so the return value is literally the number of characters that have been written into buf, and that count does not include the trailing ' '. periodt. 💖

and if size is == 0? the function returns 0. that's it. that's the whole interaction. no cap. 🦋

if you're not already dealing with a va_list, bestie, consider using scnprintf instead — that's the move, fr fr. 🔥

also!! see the vsnprintf documentation for format string extensions over C99. go read it, i'll wait. 👑

---

🌈 SEE ALSO 🌈

• Kernel file ./lib/vsprintf.c — the source, the origin story, the main character 👑
• simple_strtoull(9)
• simple_strtoul(9)
• simple_strtol(9)
• simple_strtoll(9)
• vsnprintf(9)
• snprintf(9)
• scnprintf(9)
• vsprintf(9)
• sprintf(9)
• vbin_printf(9)
• bstr_printf(9)
• vsscanf(9)
• sscanf(9)

---

okay that's the whole page, go format responsibly and don't forget the null space 💀

---

and that's a wrap!! this came at you from ./lib, dated October 2026, filed under vscnprintf(9) — slay, stay formatted, mwah 🧚💜