ceil(3)			    Library Functions Manual			 ceil(3)

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

LIBRARY
     Math library (libm, -lm)

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():
	 _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
	     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
	     || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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.

ATTRIBUTES
     For an explanation of the terms used in this  section,  see  attributes(7).
     allbox; lbx lb lb l l l.  Interface Attribute Value T{ ceil(), ceilf(),
     ceill() T}	  Thread safety	 MT-Safe

STANDARDS
     C11, POSIX.1-2008.

HISTORY
     C99, POSIX.1-2001.

     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 was
     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 127 (respectively, 1023), and the number	of  man-
     tissa  bits including the implicit bit is 24 (respectively, 53).)	This was
     removed in POSIX.1-2008.

     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  pro-
     duce  undefined results, an application should perform a range check on the
     returned value before assigning it to an integer type.

SEE ALSO
     floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)

Linux man-pages 6.18		   2026-02-08				 ceil(3)