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#### 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 ||
_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.

```

#### RETURNVALUE

```       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.

```

#### CONFORMINGTO

```       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  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.

```

#### SEEALSO

```       floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)

```

#### COLOPHON

```       This  page  is  part of release 3.35 of the Linux man-pages project.  A description of the
project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
pages/.

2010-09-20                                    CEIL(3)
```