finitef3
Bsd floating-point classification functions
Part of finite(3).
Usage
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);
_XOPEN_SOURCE {>=
600 | | _ISOC99_SOURCE}
_XOPEN_SOURCE { | | _ISOC99_SOURCE}
_XOPEN_SOURCE >=
600
Library
Math library (libm, -lm)
Overview
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
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| finite(), finitef(), finitel(), isinf(), isinff(), isinfl(), isnan(), isnanf(), isnanl() | Thread safety | MT-Safe |
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).
History
- Arch Linux 2026-11-01: the text shown here
- Debian 13 (Trixie)
- Debian 12 (Bookworm)
- Debian 11 (Bullseye)
- Debian 10 (Buster)
- Debian 9 (Stretch)
- Debian 8 (Jessie)
- Debian 7 (Wheezy)
- Debian 6.0 (Squeeze)
- Debian 5.0 (Lenny)
- Debian 4.0 (Etch)
- Debian 3.1 (Sarge)