# scalbln man page

scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl — multiply floating-point number by integral power of radix

## Synopsis

**#include <math.h>****double scalbln(double** *x***, long int** *exp***);****float scalblnf(float** *x***, long int** *exp***);****long double scalblnl(long double** *x***, long int** *exp***);****double scalbn(double** *x***, int** *exp***);****float scalbnf(float** *x***, int** *exp***);****long double scalbnl(long double** *x***, int** *exp***);**

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 versions <= 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
- An underflow floating-point exception (
**FE_UNDERFLOW**) is raised.

These functions do not set *errno*.

## 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).

## See Also

## Colophon

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## Referenced By

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