fdim - Man Page

positive difference


#include <math.h>

double fdim(double x, double y);
float fdimf(float x, float y);
long double fdiml(long double x, long double y);

Link with -lm.

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

fdimf(), fdiml():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L


These functions return the positive difference, max(x-y,0), between their arguments.

Return Value

On success, these functions return the positive difference.

If x or y is a NaN, a NaN 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: result overflow

errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised.


These functions first appeared in glibc in version 2.1.


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

fdim(), fdimf(), fdiml()Thread safetyMT-Safe

Conforming to

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


Before glibc version 2.24 on certain architectures (e.g., x86, but not x86_64) these functions did not set errno.

See Also



This page is part of release 5.13 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

fmax(3), fmin(3).

The man pages fdimf(3) and fdiml(3) are aliases of fdim(3).

2021-03-22 Linux Programmer's Manual