RINT(3P) POSIX Programmer's Manual RINT(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
rint, rintf, rintl -- round-to-nearest integral value
double rint(double x);
float rintf(float x);
long double rintl(long double x);
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.1-2008 defers to the ISO C standard.
These functions shall return the integral value (represented as a double) nearest x in the direction of the current rounding mode. The cur-
rent rounding mode is implementation-defined.
If the current rounding mode rounds toward negative infinity, then rint() shall be equivalent to floor(). If the current rounding mode
rounds toward positive infinity, then rint() shall be equivalent to ceil(). If the current rounding mode rounds towards zero, then rint()
shall be equivalent to trunc(). If the current rounding mode rounds towards nearest, then rint() differs from round() in that halfway
cases are rounded to even rather than away from zero.
These functions differ from the nearbyint(), nearbyintf(), and nearbyintl() functions only in that they may raise the inexact floating-
point exception if the result differs in value from the argument.
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 non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
Upon successful completion, these functions shall return the integer (represented as a double precision number) nearest x in the direction
of the current rounding mode. The result shall have the same sign as x.
If x is NaN, a NaN shall be returned.
If x is +-0 or +-Inf, x shall be returned.
No errors are defined.
The following sections are informative.
The integral value returned by these functions need not be expressible as an intmax_t. The return value should be tested before assigning
it to an integer type to avoid the undefined results of an integer overflow.
abs(), ceil(), feclearexcept(), fetestexcept(), floor(), isnan(), nearbyint()
The Base Definitions volume of POSIX.1-2008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, <math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
ogy -- 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.1-2008 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 Stan-
dard 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/man-pages/reporting_bugs.html .
/The Open Group 2013 RINT(3P)