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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
   attributes(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
   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 4.09 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/.

                              2016-03-15                           CEIL(3)



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