# floor 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.

floor, floorf, floorl — floor function

## Synopsis

```
#include <math.h>
double floor(double
```*x*);
float floorf(float *x*);
long double floorl(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.1‐2008 defers to the ISO C standard.

These functions shall compute the largest integral value not greater than *x*.

## Return Value

The result shall have the same sign as *x*.

Upon successful completion, these functions shall return the largest integral value not greater than *x*, expressed as a **double**, **float**, or **long double**, as appropriate for the return type of the function.

If *x* is NaN, a NaN shall be returned.

If *x* is ±0 or ±Inf, *x* shall be returned.

## Errors

No errors are defined.

*The following sections are informative.*

## Application Usage

The integral value returned by these functions might 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.

These functions may raise the inexact floating-point exception if the result differs in value from the argument.

## See Also

*ceil()*, *feclearexcept()*, *fetestexcept()*, *isnan()*

*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.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 Standard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .