# finite(3) — Linux manual page

```finite(3)               Library Functions Manual               finite(3)
```

## NAME         top

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

## LIBRARY         top

```       Math library (libm, -lm)
```

## SYNOPSIS         top

```       #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():
/* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

isinf():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

isinff(), isinfl():
/* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

isnan():
_XOPEN_SOURCE || _ISOC99_SOURCE
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

isnanf(), isnanl():
_XOPEN_SOURCE >= 600
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION         top

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

The isnan(), isnanf(), and isnanl() functions return a nonzero
value if x is a NaN value, and 0 otherwise.

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

## ATTRIBUTES         top

```       For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface                           │ Attribute     │ Value   │
├─────────────────────────────────────┼───────────────┼─────────┤
│ finite(), finitef(), finitel(),     │ Thread safety │ MT-Safe │
│ isinf(), isinff(), isinfl(),        │               │         │
│ isnan(), isnanf(), isnanl()         │               │         │
└─────────────────────────────────────┴───────────────┴─────────┘
```

## NOTES         top

```       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         top

```       This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project.  Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.