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

```
#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)):

```
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

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.

These functions return the floor of `x`

.

If `x`

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

itself is returned.

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).)

ceil(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)

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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/.