NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

NOTES

SEE ALSO

COLOPHON

## NAME

## SYNOPSIS

## DESCRIPTION

## RETURN VALUE

## ERRORS

## ATTRIBUTES

## CONFORMING TO

## NOTES

## SEE ALSO

## COLOPHON

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

NOTES

SEE ALSO

COLOPHON

ceil, ceilf, ceill − ceiling function: smallest integral value not less than argument

**#include
<math.h>**

**double
ceil(double** *x***);
float ceilf(float**

long double ceill(long double

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*

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.

These functions
return the ceiling of *x*.

If *x* is
integral, +0, −0, NaN, or infinite, *x* itself is
returned.

No errors occur. POSIX.1-2001 documents a range error for overflows, but see NOTES.

For an
explanation of the terms used in this section, see
**attributes**(7).

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

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

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.

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

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part of release 4.04 of the Linux *man-pages* project.
A description of the project, information about reporting
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http://www.kernel.org/doc/man−pages/.

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