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
   feature_test_macros(7)):

       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
       format.

       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
       attributes(7).
       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │ 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

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Linux man-pages 6.15            2025-05-17                       trunc(3)

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

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