limits(5)

NAME

limits — implementation-specific constants

SYNOPSIS

#include <limits.h>

DESCRIPTION

The following symbols are defined in <limits.h> and are used throughout the descriptive text of this manual. The column headed HP-UX Value lists the values that application writers should assume for portability across all HP-UX systems.

Symbols after values are interpreted as follows:

+: Actual limit might be greater than specified value on certain HP-UX systems.
++: Actual limit might be greater than value specified in <limits.h> on certain HP-UX systems.
-: Actual limit might be less than the specified value on certain HP-UX systems.
=: Actual limit is always equal to the specified value and does not vary across HP-UX systems.
*: The name of this limit is defined only if the preprocessor macro _XPG2 is defined, either by the compilation flag -D_XPG2, or by a #define directive in the source before <limits.h> is included in the source.
#: The value defined for this limit might not be a compile-time constant. The value defined always evaluates to an integer expression at run time.

Some of these limits vary with system configuration, and can be determined dynamically by using sysconf(2). Others can vary according to file system or device associated with a specific file, and can be determined with pathconf(2). Others are obsolescent because they are redundant with other limits or not useful in portable applications. They are provided only for importability of applications from other systems, to support applications that comply with the X/Open Portability Guide, Issue 2, and for backward compatibility with earlier versions of HP-UX. The _XPG2 flag should not be defined in new applications.

By including the <limits.h> file in the compilation an application can test the appropriate limits to determine whether it can operate on a particular system, or it might even alter its behavior to match the system to increase its portability across a varying range of limit settings and systems.

Constant	Description	HP-UX Value	Sym
`ARG_MAX`	Max length of arguments to exec(2) in bytes, including environment data	5120	+*
`CHAR_BIT`	Number of bits in a `char`	8	=
`CHAR_MAX`	Max integer value of a `char`	127	=
`CHAR_MIN`	Min integer value of a `char`	-128	=
`CHILD_MAX`	Max number of simultaneous processes per user ID	25	+-*
`CLK_TCK`	Number of clock ticks per second	50	+#
`DBL_DIG`	Digits of precision of a `double`	15	+
`DBL_MAX`	Max positive value of a `double`	1.7976931348623157e+308	+
`DBL_MIN`	Min positive value of a `double`	4.94065645841246544e-324	-
`FCHR_MAX`	Max file offset in bytes	INT_MAX	+-*
`FLT_DIG`	Digits of precision of a `float`	6	+
`FLT_MAX`	Max positive value of a `float`	3.40282346638528860e+38	+
`FLT_MIN`	Min positive value of a `float`	1.40129846432481707e-45	-
`INT_MAX`	Max decimal value of an `int`	2147483647	+
`INT_MIN`	Min decimal value of an `int`	-2147483648	-
`LINE_MAX`	Max number of characters in a single line	2048	=
`LINK_MAX`	Max number of links to a single file	32767	+*
`LOCK_MAX`	Max number of entries in system lock table	32	+-*
`LONG_BIT`	Number of bits in a `long`	32	+
`LONG_MAX`	Max decimal value of a `long`	2147483647	+
`LONG_MIN`	Min decimal value of a `long`	-2147483648	-
`MAX_CANON`	Max number of bytes in terminal canonical input line	512	+*
`MAX_CHAR`	Max number of bytes in terminal input queue	MAX_INPUT	=*
`MAX_INPUT`	Max number of bytes in terminal input queue	512	+*
`NAME_MAX`	Max number of bytes in a path name component	14	+*
`NL_ARGMAX`	Max value of "digits" in calls to the NLS printf(3S) and scanf(3S) functions	9	=
`NL_MSGMAX`	Max message number in an NLS message catalog	32767	+
`NL_SETMAX`	Max set number in an NLS message catalog	255	+
`NL_TEXTMAX`	Max number of bytes in an NLS message string	8192	+
`NGROUPS_MAX`	Max number of supplementary groups per process	20	++
`OPEN_MAX`	Max number of files a process can have open	60	+*
`PASS_MAX`	Max number of chars in a password	8	+
`PATH_MAX`	Max number of characters in a path name excluding the null terminator	1023	+*
`PID_MAX`	Max value for a process ID	30000	+
`PIPE_BUF`	Max number of bytes atomic in write to a pipe	8192	+*
`PIPE_MAX`	Max number of bytes writable to a pipe in one write	INT_MAX	+
`PROC_MAX`	Max number of simultaneous processes on system	84	+-*
`SCHAR_MAX`	Max integer value of a `signed char`	127	=
`SCHAR_MIN`	Min integer value of a `signed char`	-128	=
`SHRT_MAX`	Max decimal value of a `short`	32767	+
`SHRT_MIN`	Min decimal value of a `short`	-32768	-
`STD_BLK`	Number of bytes in a physical I/O block	512	+
`SYSPID_MAX`	Max process ID of system processes	4	+-*
`SYS_NMLN`	Length of strings returned by uname(2)	8	+*
`SYS_OPEN`	Max number of files open on system	120	+-*
`TMP_MAX`	Max number of unique names generated by tmpnam(3S)	17576	+
`UCHAR_MAX`	Max integer value of an `unsigned char`	255	=
`UID_MAX`	Smallest unattainable value for a user or group ID	2147483647	+
`UINT_MAX`	Max decimal value of an `unsigned int`	4294967295	+
`ULONG_MAX`	Max decimal value of an `unsigned long`	4294967295	+
`USHRT_MAX`	Max decimal value of an `unsigned short`	65535	+
`USI_MAX`	Max decimal value of an `unsigned int`	UINT_MAX	=*
`WORD_BIT`	Number of bits in a "word" (`int`)	32	+

EXAMPLES

UID_MAX has an HP-UX value of 2147483647 +, which means that on all HP-UX systems the smallest unattainable value for a user or group ID is at least 2147483647. A particular system might be capable of supporting more than 2147483647 user or group IDs, in which case its <limits.h> file sets UID_MAX to a higher value; however, any application assuming such a higher value is not guaranteed to be portable to all HP-UX systems.

NGROUPS_MAX has an HP-UX value of 20 ++, which means that on all HP-UX systems the smallest maximum number of supplementary groups per process is at least 20. A particular system might be capable of supporting more than 20 supplementary groups per process, in which case sysconf(_SC_NGROUPS_MAX) will return a larger value than that specified in <limits.h>; however, any application assuming such a higher value is not guaranteed to be portable to all HP-UX systems.

AUTHOR

limits was developed by HP.

STANDARDS CONFORMANCE

<limits.h>: AES, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, POSIX.2, ANSI C

limits(5)

Technical documentation

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