EXP(3) Linux Programmer's Manual EXP(3)

exp, expf, expl - base-e exponential function

#include <math.h>
double exp(double x);
float expf(float x);
long double expl(long double x);
Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
expf(), expl():
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

These functions return the value of e (the base of natural logarithms) raised to the power of x.

On success, these functions return the exponential value of x.
If x is a NaN, a NaN is returned.
If x is positive infinity, positive infinity is returned.
If x is negative infinity, +0 is returned.
If the result underflows, a range error occurs, and zero is returned.
If the result overflows, a range error occurs, and the functions return +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL, respectively.

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
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.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
exp (), expf (), expl () Thread safety MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.

cbrt(3), cexp(3), exp10(3), exp2(3), expm1(3), sqrt(3)