pr_fmt(9)

💅 pr_fmt(9) — the Kernel API Manual, bestie edition 🎀

okay so like, quick vibe check: this is a page from the Kernel API Manual and it's about pr_fmt, which is genuinely one of those tiny things that makes a whole file look put-together. main character macro energy fr fr ✨

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🌸 NAME 🌸

pr_fmt — the lil macro the pr_*() macros use to generate the printk format string 💖

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🦋 SYNOPSIS 🦋

pr_fmt (fmt );

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✨ ARGUMENTS ✨

• fmt — the format string that got passed in from a pr_*() macro. that's it. that's the whole argument 🫶

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💜 DESCRIPTION 💜

okay so here's the tea: this macro is how you generate a unified format string for all the pr_*() macros. like, one string to rule them all, no cap 👑

the classic use case — the one everybody does — is prefixing every single pr_*() message in a file with a common string. so instead of your logs looking like a chaotic group chat with no names, every message is tagged. iconic behaviour tbh.

for example, defining this at the top of a source file:

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

would prefix all pr_info, pr_emerg... messages in the file with the module name. literally all of them. slay 🔥

ngl this is the kind of one-liner that makes debugging at 3am feel slightly less cursed. slightly. 😭

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🌈 SEE ALSO 🌈

• Kernel file ./include/linux/printk.h
• printk_cpu_sync_get_irqsave(9), printk_cpu_sync_put_irqrestore(9), printk(9), pr_emerg(9), pr_alert(9), pr_crit(9), pr_err(9), pr_warn(9), pr_notice(9), pr_info(9), pr_cont(9), pr_devel(9), pr_debug(9), print_hex_dump_bytes(9)

the whole pr_* friend group, assembled 💅🍓

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aaaand that's the page bestie 🧚💫 huge shoutout to ./include/linux for hosting this one, dated October 2026 — go forth and prefix your logs, you're gonna eat 💖👑