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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 ||
           _POSIX_C_SOURCE >= 200112L;
           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  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 3.35 of the Linux man-pages project.  A description of the
       project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
       pages/.

                                            2010-09-20                                    CEIL(3)