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cbrt

Section: C Library Functions (3)
Updated: 2026-02-08
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NAME

cbrt, cbrtf, cbrtl - cube root function

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

#include <math.h>
double cbrt(double x);
float cbrtf(float x);
long double cbrtl(long double x);

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

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || _XOPEN_SOURCE >= 500
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

cbrtf(), cbrtl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

These functions return the (real) cube root of x. This function cannot fail; every representable real value has a real cube root, and rounding it to a representable value never causes overflow nor underflow.

RETURN VALUE

These functions return the cube root of x. If x is +0, -0, positive infinity, negative infinity, or NaN, x is returned.

ERRORS

No errors occur.

ATTRIBUTES

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

Interface	Attribute	Value
cbrt(), cbrtf(), cbrtl()	Thread safety	MT-Safe

STANDARDS

C11, POSIX.1-2008.

HISTORY

GNU, C99, POSIX.1-2001.