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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 || _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.
ATTRIBUTES
   Multithreading (see pthreads(7))
       The ceil(), ceilf(), and ceill() functions are thread-safe.
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  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 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2013-06-21                           CEIL(3)