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:
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: