SQRT(3) Linux Programmer's Manual SQRT(3)

sqrt, sqrtf, sqrtl - square root function 

#include <math.h>
double sqrt(double x);
float sqrtf(float x);
long double sqrtl(long double x);

Link with -lm.

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

sqrtf(), sqrtl():

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

These functions return the nonnegative square root of x.

On success, these functions return the square root of x.

If x is a NaN, a NaN is returned.

If x is +0 (-0), +0 (-0) is returned.

If x is positive infinity, positive infinity is returned.

If x is less than -0, a domain error occurs, and a NaN is returned.

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: x less than -0
errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
sqrt (), sqrtf (), sqrtl () Thread safety MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.

cbrt(3), csqrt(3), hypot(3)

This page is part of release 5.13 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
2021-03-22