## Linux and UNIX Man Pages

Test Your Knowledge in Computers #583
Difficulty: Easy
Buffered input/output is used because I/O operations can slow the system down.
True or False?

# ceil(3m) [opensolaris man page]

```ceil(3M)						  Mathematical Library Functions						  ceil(3M)

NAME
ceil, ceilf, ceill - ceiling value function

SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double ceil(double x);

float ceilf(float x);

long double ceill(long double x);

DESCRIPTION
These functions compute the smallest integral value not less than x.

RETURN VALUES
Upon  successful  completion, the ceil(), ceilf(), and ceill() functions return the smallest integral value not less than x, expressed as a
type double, float, or long double, respectively.

If x is NaN, a NaN is returned.

If x is +-0 or +-Inf, x is returned.

USAGE
The integral value returned by these functions need not be expressible as an int or long int. The return  value	should	be  tested  before
assigning it to an integer type to avoid the undefined results of an integer overflow.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+

feclearexcept(3M), fetestexcept(3M), floor(3M), isnan(3M), math.h(3HEAD), attributes(5), standards(5)

SunOS 5.11							    12 Jul 2006 							  ceil(3M)```

## Check Out this Related Man Page

```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 || _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
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 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)

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)```