CEIL(3P)                                            POSIX Programmer's Manual                                           CEIL(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       ceil, ceilf, ceill - ceiling value function

SYNOPSIS
       #include <math.h>

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


DESCRIPTION
       These functions shall compute the smallest integral value not less than x.

       An  application  wishing  to  check  for  error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)
       before calling these functions.  On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO |  FE_OVERFLOW
       | FE_UNDERFLOW) is non-zero, an error has occurred.

RETURN VALUE
       Upon  successful  completion,  ceil(),  ceilf(),  and  ceill()  shall return the smallest integral value not less than x,
       expressed as a type double, float, or long double, respectively.

       If x is NaN, a NaN shall be returned.

       If x is +-0 or +-Inf, x shall be returned.

       If the correct value would cause overflow, a range error shall occur and ceil(), ceilf(), and ceill()  shall  return  the
       value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.

ERRORS
       These functions shall fail if:

       Range Error
              The result overflows.

       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the inte-
       ger expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then  the  overflow  floating-point  exception  shall  be
       raised.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The  integral  value  returned  by  these functions need not be expressible as an int or long. The return value should be
       tested before assigning it to an integer type to avoid the undefined results of an integer overflow.

       The ceil() function can only overflow when the floating-point representation has DBL_MANT_DIG > DBL_MAX_EXP.

       On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each
       other, but at least one of them must be non-zero.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feclearexcept(),  fetestexcept(),  floor(),  isnan(),  the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18,
       Treatment of Error Conditions for Mathematical Functions, <math.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                      CEIL(3P)