# scalbln - Man Page

multiply floating-point number by integral power of radix

## Synopsis

#include <math.h> double scalbln(doublex, longexp); float scalblnf(floatx, longexp); long double scalblnl(long doublex, longexp); double scalbn(doublex, intexp); float scalbnf(floatx, intexp); long double scalbnl(long doublex, intexp);

`Link with `

*-lm*.

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

**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 *exp*, that is:

x * FLT_RADIX ** exp

The definition of **FLT_RADIX** can be obtained by including *<float.h>*.

## Return Value

On success, these functions return *x* * **FLT_RADIX** ** *exp*.

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) 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.

## Versions

These functions first appeared in glibc in version 2.1.

## Attributes

For an explanation of the terms used in this section, see attributes(7).

Interface | Attribute | Value |
---|---|---|

scalbn(), scalbnf(), scalbnl(), scalbln(), scalblnf(), scalblnl() | Thread safety | MT-Safe |

## Conforming to

C99, POSIX.1-2001, POSIX.1-2008.

## Notes

These functions differ from the obsolete functions described in scalb(3) 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) have a second argument of type *double*.

If **FLT_RADIX** equals 2 (which is usual), then **scalbn**() is equivalent to ldexp(3).

## Bugs

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

## See Also

## Colophon

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## Referenced By

The man pages scalblnf(3), scalblnl(3), scalbn(3), scalbnf(3) and scalbnl(3) are aliases of scalbln(3).