Sun Microsystems, Inc. gratefully acknowledges The Open Group for
permission to reproduce portions of its copyrighted documentation.
Original documentation from The Open Group can be obtained online at

The Institute of Electrical and Electronics Engineers and The Open
Group, have given us permission to reprint portions of their

In the following statement, the phrase ``this text'' refers to portions
of the system documentation.

Portions of this text are reprinted and reproduced in electronic form
in the SunOS Reference Manual, from IEEE Std 1003.1, 2004 Edition,
Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6,
Copyright (C) 2001-2004 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy
between these versions and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at

This notice shall appear on any product containing this material.

The Berkeley software License Agreement specifies the terms and conditions
for redistribution.

Copyright (c) 1985 Regents of the University of California.
All rights reserved.
Copyright (c) 1992, X/Open Company Limited. All Rights Reserved.
Copyright (c) 2001, The IEEE and The Open Group. All Rights Reserved.
Portions Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved.

SQRT 3M "Jul 12, 2006" "SunOS 5.11" "Mathematical Library Functions"
sqrt, sqrtf, sqrtl - square root function

c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double sqrt(double x);

float sqrtf(float x);

long double sqrtl(long double x);

These functions compute the square root of their argument x.


Upon successful completion, these functions return the square root of x.

For finite values of x < -0, a domain error occurs and either a NaN (if supported) or an implementation-defined value is returned.

If x is NaN, a NaN is returned.

If x is \(+-0 or +Inf, x is returned.

If x is -Inf, a domain error occurs and a NaN is returned.


These functions will fail if:

Domain Error

The finite value of x is < -0 or x is -Inf. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised. The sqrt() function sets errno to EDOM if the value of x is negative.


An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling sqrt(). On return, if errno is non-zero, an error has occurred. The sqrtf() and sqrtl() functions do not set errno.


See attributes(5) for descriptions of the following attributes:

Interface Stability Standard
MT-Level MT-Safe

feclearexcept(3M), fetestexcept(3M), isnan(3M), math.h(3HEAD), attributes(5), standards(5)