CEIL(3)                   (2017-09-15)                    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).     allbox;    lbw24    lb    lb   l   l   l.
          Interface Attribute Value  T{   ceil(),   ceilf(),   ceill()
          T}   Thread safety  MT-Safe

     CONFORMING TO
          C99, POSIX.1-2001, POSIX.1-2008.

          The variant returning double also conforms to SVr4,  4.3BSD,
          C89.

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     CEIL(3)                   (2017-09-15)                    CEIL(3)

     NOTES
          SUSv2 and POSIX.1-2001 contain text  about  overflow  (which
          might  set  errno  to ERANGE, or raise an FE_OVERFLOW excep-
          tion).  In practice, the result cannot overflow on any  cur-
          rent 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 5.10  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/.

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