strtoimax(3)

💖 strtoimax(3) — bestie edition 💖

okay so you know strtol(3)? this is literally that but the number gets to be huge. we're in the Library Functions Manual today, and the manual name is strtoimax — say hi bestie 🫶

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✨ NAME ✨

strtoimax, strtoumax — string to [u]intmax_t

like. you hand it a string. it hands you back the biggest integer type the C library can give you. it's giving glow up for your parsing code 💅

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📚 LIBRARY 📚

Standard C library (libc, -lc)

the classic. the blueprint. the one and only 👑

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🌸 SYNOPSIS 🌸

#include <inttypes.h>

intmax_t strtoimax(const char *restrict nptr, char **restrict endptr,
                   int base);
uintmax_t strtoumax(const char *restrict nptr, char **restrict endptr,
                    int base);

two functions, one header, zero drama ✨

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🦋 DESCRIPTION 🦋

okay so the tea:

these two are literally just like strtol(3) and strtoul(3), except — and this is the whole plot twist — they return a value of type intmax_t and uintmax_t, respectively.

that's it. that's the function. same behavior, biggest-possible-integer energy. no cap 🔥

so like, if you already know how strtol(3) works (which you do, because you're a genius), you already know how this works. go off 💜

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💫 RETURN VALUE 💫

• it worked? — you get the converted value back. slay.
• nothing was found to convert? — zero. that's it. that's the answer. 🙈
• overflow or underflow? — you get back INTMAX_MAX or INTMAX_MIN or UINTMAX_MAX (depending on which way it went off the rails), and errno is set to ERANGE.

⚠️ bestie. pay attention to errno. it is not fooling around. check it before you trust the number. INTMAX_MAX could mean "the actual answer is INTMAX_MAX" or it could mean "we blew past the limit, sorry girl." set errno to 0 first, always, fr fr 💀

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🎀 ATTRIBUTES 🎀

for an explanation of the terms used in this section, see attributes(7).

• strtoimax(), strtoumax() — Thread safety: MT-Safe locale

translation: it's MT-Safe locale, which means the safety depends on your locale vibe. you can thread it, just mind the locale, iykyk 🧚

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🌈 STANDARDS 🌈

C11, POSIX.1-2008.

certified. standardized. iconic. officially canon ✨

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🍓 HISTORY 🍓

POSIX.1-2001, C99.

so it's been around. it's not new here. it's a veteran, and it ate every single time 👑

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👑 SEE ALSO 👑

• imaxabs(3) — absolute value, but max
• imaxdiv(3) — division, but max
• strtol(3) — the blueprint
• strtoul(3) — the unsigned blueprint
• wcstoimax(3) — the wide-character cousin 🦋

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that's the whole page bestie, no notes 💅

signing off from Linux man-pages 6.20, dated 2026-07-26 — catch you in the next strtoimax(3) glow up ✨🫶💖