LIMITS(3)						   BSD Library Functions Manual 						 LIMITS(3)

NAME

     limits -- standard limits

SYNOPSIS

     #include <limits.h>

DESCRIPTION

     The <limits.h> header defines various compile-time and runtime limits.  These can be grouped into three categories:

	   1.	Compile-time limits defined in a header file.

	   2.	Runtime system limits that are not associated with a file or directory; see sysconf(3).

	   3.	Runtime limits that are associated with a file or directory; see pathconf(2).

     The <limits.h> header has been standardized by at least three entities.

   ISO Limits
     The limits defined by the ISO/IEC 9899:1999 (``ISO C99'') standard are all compile-time limits.  The numerical (integer) limits are:

	   Constant	  Type			  Minimum value
	   CHAR_BIT	  char			  8
	   SCHAR_MAX	  signed char		  127
	   SCHAR_MIN	  signed char		 -127
	   UCHAR_MAX	  unsigned char 	  255

	   INT_MAX	  int			  32767
	   INT_MIN	  int			 -32767
	   UINT_MAX	  unsigned int		  65535

	   SHRT_MIN	  short 		 -32767
	   SHRT_MAX	  short 		  32767
	   USHRT_MAX	  unsigned short	  65535

	   LONG_MAX	  long int		  2147483647
	   LONG_MIN	  long int		 -2147483647
	   ULONG_MAX	  unsigned long int	  4294967295

	   LLONG_MAX	  long long int 	  9223372036854775807
	   LLONG_MIN	  long long int 	 -9223372036854775807
	   ULLONG_MAX	  unsigned long long int  18446744073709551615

	   MB_LEN_MAX	  -			 1

     All listed limits may vary across machines and operating systems.	The standard guarantees only that the implementation-defined values are
     equal or greater in absolute value to those shown.  The values permit a system with 16-bit integers using one's complement arithmetic.

     Depending whether the system defines char as signed or unsigned, the maximum and minimum values are:

	   Constant	  Type			 Minimum value
	   CHAR_MAX	  char			 either SCHAR_MAX or UCHAR_MAX
	   CHAR_MIN	  char			 either SCHAR_MIN or 0

     The two special cases, CHAR_BIT and MB_LEN_MAX, define the number of bits in char and the maximum number of bytes in a multibyte character
     constant, respectively.

   POSIX Limits
     The POSIX.1 standard specifies numerous limits related to the operating system.  For each limit, a separate constant prefixed with
     ``_POSIX_'' defines the lowest value that the limit is allowed to have on any POSIX compliant system.  For instance, _POSIX_OPEN_MAX defines
     the minimum upper bound permitted by POSIX for the number of files that a single process may have open at any time.  This ensures that a por-
     table program can safely reach these limits without prior knowledge about the actual limits used in a particular system.

     As the limits are not necessary invariant, pathconf(2) and sysconf(3) should be used to determine the actual value of a limit at runtime.
     The manual pages of these two functions also contain a more detailed description of the limits available in NetBSD.

   XSI Limits
     Also the X/Open System Interface Extension (XSI) specifies few limits.  In NetBSD these are limited to LONG_BIT (the number of bits in long),
     WORD_BIT (the number of bits in a ``word''), and few limits related to float and double.

SEE ALSO

     getconf(1), pathconf(2), sysconf(3), types(3), unistd(3)

     Richard W. Stevens and Stephen A. Rago, Advanced Programming in the UNIX Environment, Addison-Wesley, Second Edition, 2005.

BSD
								  August 9, 2011							       BSD