Â¬â€  Â¬â€  Â¬â€  Â¬â€  Â¬â€

# FINITE

Section: Linux Programmer's Manual (3)
Updated: 2008-08-05

## NAME

finite, finitef, finitel, isinf, isinff, isinfl, isnan, isnanf, isnanl - BSD floating-point classification functions

## SYNOPSIS

```#include <math.h>

int finite(double x);

int finitef(float x);

int finitel(long double x);

int isinf(double x);

int isinff(float x);

int isinfl(long double x);

int isnan(double x);

int isnanf(float x);

int isnanl(long double x);
```

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

finite(), finitef(), finitel(): _BSD_SOURCE || _SVID_SOURCE
isinf(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; cc -std=c99
isinff(), isinfl(): _BSD_SOURCE || _SVID_SOURCE
isnan(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; cc -std=c99
isnanf(), isnanl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600

## DESCRIPTION

The finite() functions return a non-zero value if x is neither infinite nor a "not-a-number" (NaN) value, and 0 otherwise.

The isnan() functions return a non-zero value if x is a NaN value, and 0 otherwise.

The isinf() functions return 1 if x is positive infinity, -1 if x is negative infinity, and 0 otherwise.

## NOTES

Note that these functions are obsolete. C99 defines macros isfinite(), isinf(), and isnan() (for all types) replacing them. Further note that the C99 isinf() has weaker guarantees on the return value. See fpclassify(3).

fpclassify(3)

## COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

## Index

NAME
SYNOPSIS
DESCRIPTION
NOTES
COLOPHON

### Upcoming Linux Foundation Courses

05 Jan » 08 Jan - Virtual
2. LFD331 Developing Linux Device Drivers
12 Jan » 16 Jan - Virtual
3. LFS520 OpenStack Cloud Architecture and Deployment
12 Jan » 15 Jan - Virtual

View All Upcoming Courses

### Who we are ?

The Linux Foundation is a non-profit consortium dedicated to the growth of Linux.