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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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

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.

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

NOTES
       SUSv2  and  POSIX.1-2001  contain text about overflow (which might set errno 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 mantissa bits.  For the IEEE-754 standard 32-bit and 64-bit floating-point numbers the maxi-
       mum  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 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2008-08-05                           CEIL(3)