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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);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

ceilf(), ceill(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; 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 maxi-
mum  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.