lrint man page
Prolog
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
lrint, lrintf, lrintl — round to nearest integer value using current rounding direction
Synopsis
#include <math.h> long lrint(double x); long lrintf(float x); long lrintl(long double x);
Description
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.12008 defers to the ISO C standard.
These functions shall round their argument to the nearest integer value, rounding according to the current rounding direction.
An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is nonzero or fetestexcept(FE_INVALID  FE_DIVBYZERO  FE_OVERFLOW  FE_UNDERFLOW) is nonzero, an error has occurred.
Return Value
Upon successful completion, these functions shall return the rounded integer value.
If x is NaN, a domain error shall occur and an unspecified value is returned.
If x is +Inf, a domain error shall occur and an unspecified value is returned.
If x is Inf, a domain error shall occur and an unspecified value is returned.
If the correct value is positive and too large to represent as a long, an unspecified value shall be returned. On systems that support the IEC 60559 FloatingPoint option, a domain error shall occur; otherwise, a domain error may occur.
If the correct value is negative and too large to represent as a long, an unspecified value shall be returned. On systems that support the IEC 60559 FloatingPoint option, a domain error shall occur; otherwise, a domain error may occur.
Errors
These functions shall fail if:
 Domain Error

The x argument is NaN or ±Inf, or the correct value is not representable as an integer.
If the integer expression (math_errhandling & MATH_ERRNO) is nonzero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero, then the invalid floatingpoint exception shall be raised.
These functions may fail if:
 Domain Error

The correct value is not representable as an integer.
If the integer expression (math_errhandling & MATH_ERRNO) is nonzero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero, then the invalid floatingpoint exception shall be raised.
The following sections are informative.
Examples
None.
Application Usage
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be nonzero.
Rationale
These functions provide floatingtointeger conversions. They round according to the current rounding direction. If the rounded value is outside the range of the return type, the numeric result is unspecified and the invalid floatingpoint exception is raised. When they raise no other floatingpoint exception and the result differs from the argument, they raise the inexact floatingpoint exception.
Future Directions
None.
See Also
feclearexcept(), fetestexcept(), llrint()
The Base Definitions volume of POSIX.12008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, <math.h>
Copyright
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology  Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.12008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrepancy between this version 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 http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/manpages/reporting_bugs.html .