kstrtoull(9)

🦋 kstrtoull(9) 🦋

okay bestie, welcome to the kstrtoull(9) page from the Kernel API Manual 💖 this one is all about turning a string into an unsigned long long, and yes, the details matter fr fr.

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🌸 NAME 🌸

kstrtoull — convert a string to an unsigned long long ✨

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🎀 SYNOPSIS 🎀

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

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💅 ARGUMENTS 💅

• s — the start of the string, bestie. The string must be null-terminated, and it may also include a single newline before its terminating null. The first character may also be a plus sign, but not a minus sign 🙈
• base — the number base to use. The maximum supported base is 16. If base is given as 0, then the base of the string is automatically detected with the conventional semantics: if it begins with 0x the number will be parsed as a hexadecimal (case insensitive), 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 🫶

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🌈 DESCRIPTION 🌈

Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error. Preferred over simple_strtoull. Return code must be checked. no cap, do not skip that check 😭

bestie, this is the moment to be a responsible main character: check the return code. periodt 💀

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👑 SEE ALSO 👑

Kernel file ./lib/kstrtox.c — peep these icons:

• _parse_integer_limit(9)
• kstrtoll(9)
• kstrtouint(9)
• kstrtoint(9)
• kstrtobool(9)
• kstrtoudec64(9)
• kstrtodec64(9)

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mwah 💋 this lil page came from ./lib, dated October 2026, and it’s your girl kstrtoull(9) — slay and read the return code 💖✨