signbit(3) Library Functions Manual signbit(3) NAME signbit - test sign of a real floating-point number LIBRARY Math library (libm, -lm) SYNOPSIS #include int signbit(x); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): signbit(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L DESCRIPTION signbit() is a generic macro which can work on all real floating-point types. It returns a nonzero value if the value of x has its sign bit set. This is not the same as x < 0.0, because IEEE 754 floating point allows zero to be signed. The comparison -0.0 < 0.0 is false, but signbit(-0.0) will return a nonzero value. NaNs and infinities have a sign bit. RETURN VALUE The signbit() macro returns nonzero if the sign of x is negative; otherwise it returns zero. ERRORS No errors occur. ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). +--------------------------------------------+---------------+---------+ |Interface | Attribute | Value | +--------------------------------------------+---------------+---------+ |signbit () | Thread safety | MT-Safe | +--------------------------------------------+---------------+---------+ STANDARDS C11, POSIX.1-2008. HISTORY POSIX.1-2001, C99. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854). SEE ALSO copysign(3) Linux man-pages 6.9.1 2024-05-02 signbit(3)