ceil

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

NAME
       ceil, ceilf, ceill - ceiling function: smallest integral value not less
       than argument

SYNOPSIS
       #include <math.h>

       double ceil(double x);
       float ceilf(float x);
       long double ceill(long double x);

       Link with -lm.

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

       ceilf(), ceill():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       These functions return the smallest integral value  that  is  not  less
       than x.

       For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.

RETURN VALUE
       These functions return the ceiling of x.

       If x is integral, +0, -0, NaN, or infinite, x itself is returned.

ERRORS
       No  errors  occur.  POSIX.1-2001 documents a range error for overflows,
       but see NOTES.

ATTRIBUTES
       For an  explanation  of  the  terms  used  in  this  section,  see  at-
       tributes(7).

       +-------------------------+---------------+---------+
       |Interface                | Attribute     | Value   |
       +-------------------------+---------------+---------+
       |ceil(), ceilf(), ceill() | Thread safety | MT-Safe |
       +-------------------------+---------------+---------+
CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

NOTES
       SUSv2 and POSIX.1-2001 contain text about overflow (which might set er-
       rno to ERANGE, or raise an FE_OVERFLOW exception).   In  practice,  the
       result  cannot  overflow on any current machine, so this error-handling
       stuff is just nonsense.  (More precisely, overflow can happen only when
       the  maximum  value  of the exponent is smaller than the number of man-
       tissa bits.  For the IEEE-754 standard 32-bit and 64-bit floating-point
       numbers  the maximum value of the exponent is 128 (respectively, 1024),
       and the number of mantissa bits is 24 (respectively, 53).)

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

COLOPHON
       This page is part of release 5.05 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/.

                                  2017-09-15                           CEIL(3)