# scalb - Man Page

multiply floating-point number by integral power of radix (OBSOLETE)

## Synopsis

#include <math.h> double scalb(doublex, doubleexp); float scalbf(floatx, floatexp); long double scalbl(long doublex, long doubleexp);

`Link with `

*-lm*.

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

**scalb**():

_XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

**scalbf**(), **scalbl**():

_XOPEN_SOURCE >= 600 || /* 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* or *exp* is a NaN, a NaN is returned.

If *x* is positive infinity (negative infinity), and *exp* is not negative infinity, positive infinity (negative infinity) is returned.

If *x* is +0 (-0), and *exp* is not positive infinity, +0 (-0) is returned.

If *x* is zero, and *exp* is positive infinity, a domain error occurs, and a NaN is returned.

If *x* is an infinity, and *exp* is negative infinity, a domain error occurs, and a NaN 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:

- Domain error:
*x*is 0, and*exp*is positive infinity, or*x*is positive infinity and*exp*is negative infinity and the other argument is not a NaN *errno*is set to**EDOM**. An invalid floating-point exception (**FE_INVALID**) is raised.- Range error, overflow
*errno*is set to**ERANGE**. 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).

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

scalb(), scalbf(), scalbl() | Thread safety | MT-Safe |

## Conforming to

**scalb**() is specified in POSIX.1-2001, but marked obsolescent. POSIX.1-2008 removes the specification of **scalb**(), recommending the use of scalbln(3), scalblnf(3), or scalblnl(3) instead. The **scalb**() function is from 4.3BSD.

**scalbf**() and **scalbl**() are unstandardized; **scalbf**() is nevertheless present on several other systems

## Bugs

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

## See Also

## Colophon

This page is part of release 5.11 of the Linux *man-pages* project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

## Referenced By

The man pages scalbf(3) and scalbl(3) are aliases of scalb(3).