---
name: "scalbln"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/scalbln"
---

# scalbln(3)

scale by an integer power of radix

## NAME

scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl - scale by an integer power of radix

## LIBRARY

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

## SYNOPSIS

```
#include <math.h>
```

**double scalbln(double** *x***, long** *e***);** **float scalblnf(float** *x***, long** *e***);** **long double scalblnl(long double** *x***, long** *e***);**

**double scalbn(double** *x***, int** *e***);** **float scalbnf(float** *x***, int** *e***);** **long double scalbnl(long double** *x***, int** *e***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**scalbln**(), **scalblnf**(), **scalblnl**():

```
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
```

**scalbn**(), **scalbnf**(), **scalbnl**():

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

## DESCRIPTION

These functions multiply their first argument *x* by **FLT\_RADIX** (probably 2) to the power of *e*, that is:

```
    x * FLT_RADIX ** e
```

The definition of **FLT\_RADIX** can be obtained by including *\<float.h\>*.

## RETURN VALUE

On success, these functions return *x* \* **FLT\_RADIX** \*\* *e*.

If *x* is a NaN, a NaN is returned.

If *x* is positive infinity (negative infinity), positive infinity (negative infinity) is returned.

If *x* is +0 (-0), +0 (-0) is returned.

If the result overflows, a range error occurs, and the functions return **HUGE\_VAL**, **HUGE\_VALF**, or **HUGE\_VALL**, respectively, with a sign the same as *x*.

If the result underflows, a range error occurs, and the functions return zero, with a sign the same as *x*.

## ERRORS

See [**math\_error**(7)](/math_error/7.md) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

- Range error, overflow

  An overflow floating-point exception (**FE\_OVERFLOW**) is raised.

- Range error, underflow

  *errno* is set to **ERANGE**. An underflow floating-point exception (**FE\_UNDERFLOW**) is raised.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **scalbn**(), **scalbnf**(), **scalbnl**(), **scalbln**(), **scalblnf**(), **scalblnl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## HISTORY

These functions differ from the obsolete functions described in [**scalb**(3)](/scalb/3.md) in the type of their second argument. The functions described on this page have a second argument of an integral type, while those in [**scalb**(3)](/scalb/3.md) have a second argument of type *double*.

## NOTES

If **FLT\_RADIX** equals 2 (which is usual), then **scalbn**() is equivalent to [**ldexp**(3)](/ldexp/3.md).

## BUGS

Before glibc 2.20, these functions did not set *errno* for range errors.

## SEE ALSO

[**ldexp**(3)](/ldexp/3.md), [**scalb**(3)](/scalb/3.md)