ecvt_r(3)

✨ ecvt_r(3) ✨ — the <rainbow>convert a float to a string, but make it thread-safe-ish</rainbow> page

okay bestie, sit down, hydrate, because we're talking about ecvt_r(3) from the Library Functions Manual 💖

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🌸 NAME 🌸

ecvt_r, fcvt_r, qecvt_r, qfcvt_r — convert a floating-point number to a string 💅

📚 LIBRARY 📚

Standard C library (libc, -lc) 🎀

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✨ SYNOPSIS ✨

#include <stdlib.h>

[[deprecated]] int ecvt_r(double number, int ndigits,
                          int *restrict decpt, int *restrict sign,
                          char *restrict buf, size_t size);
[[deprecated]] int fcvt_r(double number, int ndigits,
                          int *restrict decpt, int *restrict sign,
                          char *restrict buf, size_t size);

[[deprecated]] int qecvt_r(long double number, int ndigits,
                           int *restrict decpt, int *restrict sign,
                           char *restrict buf, size_t size);
[[deprecated]] int qfcvt_r(long double number, int ndigits,
                           int *restrict decpt, int *restrict sign,
                           char *restrict buf, size_t size);

👀 notice the [[deprecated]] on literally every single one of these, bestie. the compiler is screaming at you. listen to it.

🧚 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

ecvt_r(), fcvt_r(), qecvt_r(), qfcvt_r():
    /* glibc >= 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

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💖 DESCRIPTION 💖

so like. ecvt_r(), fcvt_r(), qecvt_r(), and qfcvt_r() are identical to ecvt(3), fcvt(3), qecvt(3), and qfcvt(3) respectively — except for one lil glow-up: they do not return their result in a static buffer 🙈. instead they use the buf you supply, which is size big. that's the whole vibe. go read ecvt(3) and qecvt(3) for the actual deets 💫

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🫶 RETURN VALUE 🫶

• 0 — slay, success ✨
• -1 — otherwise 😭

👑 ATTRIBUTES 👑

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

• Interface: ecvt_r(), fcvt_r(), qecvt_r(), qfcvt_r()
• Attribute: Thread safety
• Value: MT-Safe 💅

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📜 STANDARDS 📜

GNU. yeah. GNU. that's it. that's the standard.

💀 NOTES 💀

okay so real talk: these functions are obsolete. like, they're giving "still works but everyone's side-eyeing you" energy. instead, sprintf(3) is recommended. periodt. 🎀

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🌈 SEE ALSO 🌈

• ecvt(3)
• qecvt(3)
• sprintf(3)

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okay that's the whole page, bestie, you ate that 🍓💜 — this was Linux man-pages 6.20, dated 2026-02-08, and it's the ecvt_r(3) page, so go call sprintf(3) instead, ily, bye 👑🦋