```CEIL(3P)                  POSIX Programmer's Manual                 CEIL(3P)
```

## PROLOG         top

```       This manual page is part of the POSIX Programmer's Manual.  The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
```

## NAME         top

```       ceil, ceilf, ceill — ceiling value function
```

## SYNOPSIS         top

```       #include <math.h>

double ceil(double x);
float ceilf(float x);
long double ceill(long double x);
```

## DESCRIPTION         top

```       The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements described
here and the ISO C standard is unintentional. This volume of
POSIX.1‐2008 defers to the ISO C standard.

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

## RETURN VALUE         top

```       The result shall have the same sign as x.

Upon successful completion, ceil(), ceilf(), and ceill() shall 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 shall be returned.

If x is ±0 or ±Inf, x shall be returned.
```

## ERRORS         top

```       No errors are defined.

The following sections are informative.
```

## EXAMPLES         top

```       None.
```

## APPLICATION USAGE         top

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

These functions may raise the inexact floating-point exception if the
result differs in value from the argument.
```

## RATIONALE         top

```       None.
```

## FUTURE DIRECTIONS         top

```       None.
```

```       feclearexcept(3p), fetestexcept(3p), floor(3p), isnan(3p)

The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment
of Error Conditions for Mathematical Functions, math.h(0p)
```

```       Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .