kstrtol(9)

💅 kstrtol(9) — the manual page, but make it make sense

okay so bestie, this is kstrtol from the Kernel API Manual, and it's literally the glow-up version of turning a string into a long. no cap. let's get into it 🫶

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✨ NAME ✨

kstrtol — convert a string to a long. that's it. that's the whole vibe check. 🎀

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🌸 SYNOPSIS 🌸

int kstrtol (const char *s , unsigned int base , long *res );

look at her. three args, one int coming back. iconic. 👑

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🦋 ARGUMENTS 🦋

• s — the start of the string. this is the main character of the whole function ngl. she must be null-terminated, and she may also include a single newline before her terminating null (just one, don't get greedy 💀). and listen — the first character may also be a plus sign or a minus sign. yes bestie, she's flexible like that ✨
• base — the number base to use. the maximum supported base is 16, so don't come at her with base 17, she's not doing it 🙈. but here's the cute part: if base is given as 0, then the base of the string is automatically detected with the conventional semantics — like, she reads the room 💅:
  • if it begins with 0x the number will be parsed as a hexadecimal (case insensitive, she doesn't care if you scream 0X or whisper 0x)
  • if it otherwise begins with 0, it will be parsed as an octal number
  • otherwise it will be parsed as a decimal
• res — where to write the result of the conversion on success. this is the lil drop-off spot. she leaves the answer here 🎁

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💜 DESCRIPTION 💜

okay so here's the tea: returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error. those are the only three plot twists 🍓

this function is preferred over simple_strtol — she's the upgrade, the newer model, the one you actually want. and the return code must be checked. like, literally non-negotiable.

⚠️ bestie please. check that return code. i am begging. do not just call kstrtol and walk away like nothing happened 😭 the return code must be checked. that's not a suggestion, that's the whole point.

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🌈 SEE ALSO 🌈

• Kernel file: ./include/linux/kstrtox.h
• kstrtoul(9)

go read the header, she has lore 🧚

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and that's the page, bestie 💖 this gem lives with the rest of the kernel docs under ./include/linux, dated October 2026. slay, stay safe, and please check your return codes. periodt. 💅✨🦋