trunc(3) — Linux manual page


trunc(3)                Library Functions Manual                trunc(3)

NAME         top

       trunc, truncf, truncl - round to integer, toward zero

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #include <math.h>

       double trunc(double x);
       float truncf(float x);
       long double truncl(long double x);

   Feature Test Macro Requirements for glibc (see

       trunc(), truncf(), truncl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION         top

       These functions round x to the nearest integer value that is not
       larger in magnitude than x.

RETURN VALUE         top

       These functions return the rounded integer value, in floating

       If x is integral, infinite, or NaN, x itself is returned.

ERRORS         top

       No errors occur.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ trunc(), truncf(), truncl()         │ Thread safety │ MT-Safe │

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       glibc 2.1.  C99, POSIX.1-2001.

NOTES         top

       The integral value returned by these functions may be too large
       to store in an integer type (int, long, etc.).  To avoid an
       overflow, which will produce undefined results, an application
       should perform a range check on the returned value before
       assigning it to an integer type.

SEE ALSO         top

       ceil(3), floor(3), lrint(3), nearbyint(3), rint(3), round(3)

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨⟩.  If you have a bug report
       for this manual page, see
       This page was obtained from the tarball man-pages-6.9.1.tar.gz
       fetched from
       ⟨⟩ on
       2024-06-26.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
       to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to

Linux man-pages 6.9.1          2024-05-02                       trunc(3)

Pages that refer to this page: ceil(3)floor(3)rint(3)round(3)