floor - calculate the floor of a number

floor, floorf, floorl - largest integral value not greater than argument

`#include <math.h>`

```
double floor(double x);
```

```
#include <math.h>
double floor(double x);
float floorf(float x);
long double floorl(long double x);
```

Link with `-lm`

.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

This function returns the floor of `x`

.

These functions return the largest integral value that is not greater than `x`

.

For example, `floor(0.5)`

is 0.0, and `floor(-0.5)`

is -1.0.

This function returns, as a `double`

, the largest integer that is not greater than `x`

. You may safely cast that value to a `long`

(or an `int`

if it fits).

These functions return the floor of `x`

.

If `x`

is integral, +0, -0, NaN, or an infinity, `x`

itself is returned.

`#include <math.h>`

#include <stdio.h>

int main(void)
{
printf("This is CS%i\n", (int) floor(50.1));
}

No errors occur. POSIX.1-2001 documents a range error for overflows, but see NOTES.

For an explanation of the terms used in this section, see attributes(7).

Interface | Attribute | Value |

floor(), floorf(), floorl() | Thread safety | MT-Safe |

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning `double`

also conforms to SVr4, 4.3BSD, C89.

SUSv2 and POSIX.1-2001 contain text about overflow (which might set `errno`

to **ERANGE**, or raise an **FE_OVERFLOW** exception). In practice, the result cannot overflow on any current machine, so this error-handling stuff is just nonsense. (More precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of mantissa bits. For the IEEE-754 standard 32-bit and 64-bit floating-point numbers the maximum value of the exponent is 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively, 53).)

This page is part of release 5.10 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/.