xbc_snprint_cmdline(9)

💅 xbc_snprint_cmdline — the Kernel API Manual, bestie edition 🎀

okay so you know how bootconfig keys are just sitting there being all tree-shaped and mysterious? ✨ This is the function that takes them and turns them into one (1) cute lil cmdline string. It's xbc_snprint_cmdline, and it lives in the Kernel API Manual (xbc_snprint_cmdline(9)) — yes, section 9, we love a kernel-internals moment. 🫶

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✨ NAME ✨

xbc_snprint_cmdline — renders bootconfig keys under @root as a cmdline string 💖

🌸 SYNOPSIS 🌸

int xbc_snprint_cmdline (char *buf , size_t size , struct xbc_node *root
);

🦋 ARGUMENTS 🦋

• buf — your destination buffer, bestie. And get this: it can totally be NULL when size is 0, because that's the little query-the-length hack — you're just asking "how much room do I need" without writing a single byte. 🎀
• size — how big buf is, in bytes. that's it, that's the whole vibe check. 📏
• root — the subtree root whose key=value pairs should be rendered. this is the main character of the whole operation ngl 👑

💜 DESCRIPTION 💜

So the whole thing is a walk — it walks all the key/value pairs under root and emits them as a space-separated cmdline string into buf. iconique. 🌈

Values that contain whitespace? Those get quoted with double quotes, because obviously we're not letting a space break the whole cmdline. " around it and we move on. 💅

And it returns — okay this part is so important — the number of bytes that would be written if buf were large enough. matching snprintf semantics, iykyk. So even when the buffer is too small you still get the real length back, which is exactly how you're supposed to do the two-pass thing. ✨

🫶 friendly heads up: on failure it returns a negative errno. so like, if the return is negative, it's not a length, it's a scream. check it. 😭

🧚 SEE ALSO 🧚

Kernel file ./lib/bootconfig.c — and honestly the whole friend group shows up here:

• xbc_prepend_embedded_cmdline(9)
• xbc_embedded_cmdline_applied(9)
• bootconfig_cmdline_requested(9)
• xbc_get_info(9)
• xbc_root_node(9)
• xbc_node_index(9)
• xbc_node_get_parent(9)
• xbc_node_get_child(9)
• xbc_node_get_next(9)
• xbc_node_get_data(9)
• xbc_node_find_subkey(9)
• xbc_node_find_value(9)
• xbc_node_compose_key_after(9)
• xbc_node_find_next_leaf(9)
• xbc_node_find_next_key_value(9)
• _xbc_exit(9)
• xbc_init(9)

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that's the whole page, no crumbs left 💀✨ go render some keys, you're gonna ate it up. 🔥

sign-off szn 🎀 — this page came from ./lib, dated October 2026, and it's xbc_snprint_cmdline(9) in the Kernel API Manual. mwah 💋