#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():

_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;

or cc -std=c99

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


or cc -std=c99


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>.


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.


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.


These functions first appeared in glibc in version 2.1.


Multithreading (see pthreads(7))

The scalbn(), scalbnf(), scalbnl(), scalbln(), scalblnf(), and scalblnl() functions are thread-safe.


C99, POSIX.1-2001.


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).

RELATED TO scalbnl…


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