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signbit
<html> <head> <title>signbit</title> <META NAME="KEYWORDS" CONTENT="signbit"> </head> <body BGCOLOR="#ffffff" LINK="#0000ff" VLINK="#0000ff" ALINK="#0000ff" TEXT="#000000"> <center> <h1><b>signbit</b></h1></center> <PRE> <STRONG><A HREF="/man3/SIGNBIT">SIGNBIT(3)</A></STRONG> Linux Programmer's Manual <STRONG><A HREF="/man3/SIGNBIT">SIGNBIT(3)</A></STRONG> NAME signbit - test sign of a real floating-point number SYNOPSIS #include <math.h> int signbit(x); Link with -lm. Feature Test Macro Requirements for glibc (see <STRONG><A HREF="/man7/feature_test_macros">feature_test_macros(7)</A></STRONG>): 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 sign- bit(-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; oth- erwise it returns zero. ERRORS No errors occur. ATTRIBUTES For an explanation of the terms used in this section, see at- <STRONG><A HREF="/man7/tributes">tributes(7)</A></STRONG>. +----------+---------------+---------+ |Interface | Attribute | Value | +----------+---------------+---------+ |signbit() | Thread safety | MT-Safe | +----------+---------------+---------+ CONFORMING TO POSIX.1-2001, POSIX.1-2008, C99. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854). SEE ALSO <STRONG><A HREF="/man3/copysign">copysign(3)</A></STRONG> COLOPHON This page is part of release 5.05 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/. GNU 2017-09-15 <STRONG><A HREF="/man3/SIGNBIT">SIGNBIT(3)</A></STRONG></PRE> <center> <h6>Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2025 <a href="http://www.he.net">Hurricane Electric</a>. All Rights Reserved.</h6></center> </body> </html>