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<limits.h>(0P)		   POSIX Programmer's Manual		<limits.h>(0P)

NAME
       limits.h - implementation-defined constants

SYNOPSIS
       #include <limits.h>

DESCRIPTION
       Some  of the functionality described on this reference page extends the
       ISO C standard. Applications shall define the appropriate feature  test
       macro  (see  the System Interfaces volume of IEEE Std 1003.1-2001, Sec‐
       tion 2.2, The Compilation Environment)  to  enable  the	visibility  of
       these symbols in this header.

       Many   of   the	 symbols   listed   here   are	 not  defined  by  the
       ISO/IEC 9899:1999 standard. Such symbols are not shown as CX shaded.

       The <limits.h> header shall define various  symbolic  names.  Different
       categories of names are described below.

       The names represent various limits on resources that the implementation
       imposes on applications.

       Implementations may choose any appropriate value for each  limit,  pro‐
       vided  it  is  not  more restrictive than the Minimum Acceptable Values
       listed below. Symbolic constant names  beginning	 with  _POSIX  may  be
       found in <unistd.h> .

       Applications  should  not  assume  any particular value for a limit. To
       achieve maximum portability, an application  should  not	 require  more
       resource	 than  the  Minimum  Acceptable	 Value	quantity.  However, an
       application wishing to avail itself of the full amount  of  a  resource
       available on an implementation may make use of the value given in <lim‐
       its.h> on that particular implementation, by using the  symbolic	 names
       listed below. It should be noted, however, that many of the listed lim‐
       its are not invariant, and at runtime, the value of the limit may  dif‐
       fer from those given in this header, for the following reasons:

	* The limit is pathname-dependent.

	* The limit differs between the compile and runtime machines.

       For  these reasons, an application may use the fpathconf(), pathconf(),
       and sysconf() functions to determine the actual value  of  a  limit  at
       runtime.

       The items in the list ending in _MIN give the most negative values that
       the mathematical types are guaranteed to be  capable  of	 representing.
       Numbers	of  a more negative value may be supported on some implementa‐
       tions, as indicated by the <limits.h> header on the implementation, but
       applications  requiring	such numbers are not guaranteed to be portable
       to all implementations. For positive constants  ending  in  _MIN,  this
       indicates the minimum acceptable value.

   Runtime Invariant Values (Possibly Indeterminate)
       A  definition  of one of the symbolic names in the following list shall
       be omitted from <limits.h> on specific implementations where the corre‐
       sponding	 value	is equal to or greater than the stated minimum, but is
       unspecified.

       This indetermination might depend on the	 amount	 of  available	memory
       space  on a specific instance of a specific implementation.  The actual
       value supported by  a  specific	instance  shall	 be  provided  by  the
       sysconf() function.

       {AIO_LISTIO_MAX}

	      Maximum  number of I/O operations in a single list I/O call sup‐
	      ported by the implementation.
	      Minimum Acceptable Value: {_POSIX_AIO_LISTIO_MAX}

       {AIO_MAX}

	      Maximum number of outstanding asynchronous I/O  operations  sup‐
	      ported by the implementation.
	      Minimum Acceptable Value: {_POSIX_AIO_MAX}

       {AIO_PRIO_DELTA_MAX}

	      The maximum amount by which a process can decrease its asynchro‐
	      nous I/O priority level from its own scheduling priority.
	      Minimum Acceptable Value: 0

       {ARG_MAX}
	      Maximum length of argument to the exec functions including envi‐
	      ronment data.
	      Minimum Acceptable Value: {_POSIX_ARG_MAX}

       {ATEXIT_MAX}

	      Maximum	number	of  functions  that  may  be  registered  with
	      atexit().
	      Minimum Acceptable Value: 32

       {CHILD_MAX}
	      Maximum number of simultaneous processes per real user ID.
	      Minimum Acceptable Value: {_POSIX_CHILD_MAX}

       {DELAYTIMER_MAX}

	      Maximum number of timer expiration overruns.
	      Minimum Acceptable Value: {_POSIX_DELAYTIMER_MAX}

       {HOST_NAME_MAX}
	      Maximum length of a host name  (not  including  the  terminating
	      null) as returned from the gethostname() function.
	      Minimum Acceptable Value: {_POSIX_HOST_NAME_MAX}

       {IOV_MAX}

	      Maximum  number  of iovec structures that one process has avail‐
	      able for use with readv() or writev().
	      Minimum Acceptable Value: {_XOPEN_IOV_MAX}

       {LOGIN_NAME_MAX}
	      Maximum length of a login name.
	      Minimum Acceptable Value: {_POSIX_LOGIN_NAME_MAX}

       {MQ_OPEN_MAX}

	      The maximum number of open message queue descriptors  a  process
	      may hold.
	      Minimum Acceptable Value: {_POSIX_MQ_OPEN_MAX}

       {MQ_PRIO_MAX}

	      The maximum number of message priorities supported by the imple‐
	      mentation.
	      Minimum Acceptable Value: {_POSIX_MQ_PRIO_MAX}

       {OPEN_MAX}
	      Maximum number of files that one process can have	 open  at  any
	      one time.
	      Minimum Acceptable Value: {_POSIX_OPEN_MAX}

       {PAGESIZE}
	      Size in bytes of a page.
	      Minimum Acceptable Value: 1

       {PAGE_SIZE}

	      Equivalent to {PAGESIZE}. If either {PAGESIZE} or {PAGE_SIZE} is
	      defined, the other is defined with the same value.

       {PTHREAD_DESTRUCTOR_ITERATIONS}

	      Maximum number of attempts made to destroy  a  thread's  thread-
	      specific data values on thread exit.
	      Minimum Acceptable Value: {_POSIX_THREAD_DESTRUCTOR_ITERATIONS}

       {PTHREAD_KEYS_MAX}

	      Maximum number of data keys that can be created by a process.
	      Minimum Acceptable Value: {_POSIX_THREAD_KEYS_MAX}

       {PTHREAD_STACK_MIN}

	      Minimum size in bytes of thread stack storage.
	      Minimum Acceptable Value: 0

       {PTHREAD_THREADS_MAX}

	      Maximum number of threads that can be created per process.
	      Minimum Acceptable Value: {_POSIX_THREAD_THREADS_MAX}

       {RE_DUP_MAX}
	      The  number  of  repeated	 occurrences of a BRE permitted by the
	      regexec() and regcomp() functions when using the interval	 nota‐
	      tion {\(m,n\}; see BREs Matching Multiple Characters .
	      Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}

       {RTSIG_MAX}

	      Maximum  number of realtime signals reserved for application use
	      in this implementation.
	      Minimum Acceptable Value: {_POSIX_RTSIG_MAX}

       {SEM_NSEMS_MAX}

	      Maximum number of semaphores that a process may have.
	      Minimum Acceptable Value: {_POSIX_SEM_NSEMS_MAX}

       {SEM_VALUE_MAX}

	      The maximum value a semaphore may have.
	      Minimum Acceptable Value: {_POSIX_SEM_VALUE_MAX}

       {SIGQUEUE_MAX}

	      Maximum number of queued signals that a  process	may  send  and
	      have pending at the receiver(s) at any time.
	      Minimum Acceptable Value: {_POSIX_SIGQUEUE_MAX}

       {SS_REPL_MAX}

	      The  maximum  number  of	replenishment  operations  that may be
	      simultaneously pending for a particular sporadic	server	sched‐
	      uler.
	      Minimum Acceptable Value: {_POSIX_SS_REPL_MAX}

       {STREAM_MAX}
	      The  number  of  streams	that  one process can have open at one
	      time.  If defined, it has the same  value	 as  {FOPEN_MAX}  (see
	      <stdio.h> ).
	      Minimum Acceptable Value: {_POSIX_STREAM_MAX}

       {SYMLOOP_MAX}
	      Maximum  number of symbolic links that can be reliably traversed
	      in the resolution of a pathname in the absence of a loop.
	      Minimum Acceptable Value: {_POSIX_SYMLOOP_MAX}

       {TIMER_MAX}

	      Maximum number of timers per process supported by the  implemen‐
	      tation.
	      Minimum Acceptable Value: {_POSIX_TIMER_MAX}

       {TRACE_EVENT_NAME_MAX}

	      Maximum length of the trace event name.
	      Minimum Acceptable Value: {_POSIX_TRACE_EVENT_NAME_MAX}

       {TRACE_NAME_MAX}

	      Maximum  length of the trace generation version string or of the
	      trace stream name.
	      Minimum Acceptable Value: {_POSIX_TRACE_NAME_MAX}

       {TRACE_SYS_MAX}

	      Maximum number of trace streams that may simultaneously exist in
	      the system.
	      Minimum Acceptable Value: {_POSIX_TRACE_SYS_MAX}

       {TRACE_USER_EVENT_MAX}

	      Maximum  number  of  user	 trace event type identifiers that may
	      simultaneously exist in a traced process, including  the	prede‐
	      fined user trace event POSIX_TRACE_UNNAMED_USER_EVENT.
	      Minimum Acceptable Value: {_POSIX_TRACE_USER_EVENT_MAX}

       {TTY_NAME_MAX}
	      Maximum length of terminal device name.
	      Minimum Acceptable Value: {_POSIX_TTY_NAME_MAX}

       {TZNAME_MAX}
	      Maximum  number  of  bytes  supported for the name of a timezone
	      (not of the TZ variable).
	      Minimum Acceptable Value: {_POSIX_TZNAME_MAX}

       Note:  The length given by {TZNAME_MAX} does not	 include  the  quoting
	      characters mentioned in Other Environment Variables .

   Pathname Variable Values
       The values in the following list may be constants within an implementa‐
       tion or may vary from one pathname to another. For example,  file  sys‐
       tems or directories may have different characteristics.

       A  definition of one of the values shall be omitted from the <limits.h>
       header on specific implementations where	 the  corresponding  value  is
       equal  to  or  greater than the stated minimum, but where the value can
       vary depending on the file to which it is  applied.  The	 actual	 value
       supported  for  a specific pathname shall be provided by the pathconf()
       function.

       {FILESIZEBITS}
	      Minimum number of bits needed to represent, as a signed  integer
	      value,  the maximum size of a regular file allowed in the speci‐
	      fied directory.
	      Minimum Acceptable Value: 32

       {LINK_MAX}
	      Maximum number of links to a single file.
	      Minimum Acceptable Value: {_POSIX_LINK_MAX}

       {MAX_CANON}
	      Maximum number of bytes in a terminal canonical input line.
	      Minimum Acceptable Value: {_POSIX_MAX_CANON}

       {MAX_INPUT}
	      Minimum number of bytes for which space is available in a termi‐
	      nal  input  queue; therefore, the maximum number of bytes a con‐
	      forming application may require to  be  typed  as	 input	before
	      reading them.
	      Minimum Acceptable Value: {_POSIX_MAX_INPUT}

       {NAME_MAX}
	      Maximum number of bytes in a filename (not including terminating
	      null).
	      Minimum Acceptable Value: {_POSIX_NAME_MAX}
	      Minimum Acceptable Value: {_XOPEN_NAME_MAX}

       {PATH_MAX}
	      Maximum number of bytes in a pathname, including the terminating
	      null character.
	      Minimum Acceptable Value: {_POSIX_PATH_MAX}
	      Minimum Acceptable Value: {_XOPEN_PATH_MAX}

       {PIPE_BUF}
	      Maximum  number  of  bytes  that is guaranteed to be atomic when
	      writing to a pipe.
	      Minimum Acceptable Value: {_POSIX_PIPE_BUF}

       {POSIX_ALLOC_SIZE_MIN}

	      Minimum number of bytes of storage actually  allocated  for  any
	      portion of a file.
	      Minimum Acceptable Value: Not specified.

       {POSIX_REC_INCR_XFER_SIZE}

	      Recommended  increment  for  file	 transfer  sizes  between  the
	      {POSIX_REC_MIN_XFER_SIZE} and {POSIX_REC_MAX_XFER_SIZE} values.
	      Minimum Acceptable Value: Not specified.

       {POSIX_REC_MAX_XFER_SIZE}

	      Maximum recommended file transfer size.
	      Minimum Acceptable Value: Not specified.

       {POSIX_REC_MIN_XFER_SIZE}

	      Minimum recommended file transfer size.
	      Minimum Acceptable Value: Not specified.

       {POSIX_REC_XFER_ALIGN}

	      Recommended file transfer buffer alignment.
	      Minimum Acceptable Value: Not specified.

       {SYMLINK_MAX}
	      Maximum number of bytes in a symbolic link.
	      Minimum Acceptable Value: {_POSIX_SYMLINK_MAX}

   Runtime Increasable Values
       The magnitude limitations in the following list shall be fixed by  spe‐
       cific implementations. An application should assume that the value sup‐
       plied by <limits.h> in a specific implementation is  the	 minimum  that
       pertains	 whenever  the application is run under that implementation. A
       specific instance of a specific implementation may increase  the	 value
       relative	 to  that  supplied by <limits.h> for that implementation. The
       actual value supported by a specific instance shall be provided by  the
       sysconf() function.

       {BC_BASE_MAX}
	      Maximum obase values allowed by the bc utility.
	      Minimum Acceptable Value: {_POSIX2_BC_BASE_MAX}

       {BC_DIM_MAX}
	      Maximum number of elements permitted in an array by the bc util‐
	      ity.
	      Minimum Acceptable Value: {_POSIX2_BC_DIM_MAX}

       {BC_SCALE_MAX}
	      Maximum scale value allowed by the bc utility.
	      Minimum Acceptable Value: {_POSIX2_BC_SCALE_MAX}

       {BC_STRING_MAX}
	      Maximum length of a string constant accepted by the bc utility.
	      Minimum Acceptable Value: {_POSIX2_BC_STRING_MAX}

       {CHARCLASS_NAME_MAX}
	      Maximum number of bytes in a character class name.
	      Minimum Acceptable Value: {_POSIX2_CHARCLASS_NAME_MAX}

       {COLL_WEIGHTS_MAX}
	      Maximum number of weights that can be assigned to	 an  entry  of
	      the  LC_COLLATE order keyword in the locale definition file; see
	      Locale .
	      Minimum Acceptable Value: {_POSIX2_COLL_WEIGHTS_MAX}

       {EXPR_NEST_MAX}
	      Maximum number of expressions that can be nested	within	paren‐
	      theses by the expr utility.
	      Minimum Acceptable Value: {_POSIX2_EXPR_NEST_MAX}

       {LINE_MAX}
	      Unless otherwise noted, the maximum length, in bytes, of a util‐
	      ity's input line (either standard input or another  file),  when
	      the  utility  is	described as processing text files. The length
	      includes room for the trailing <newline>.
	      Minimum Acceptable Value: {_POSIX2_LINE_MAX}

       {NGROUPS_MAX}
	      Maximum number  of  simultaneous	supplementary  group  IDs  per
	      process.
	      Minimum Acceptable Value: {_POSIX_NGROUPS_MAX}

       {RE_DUP_MAX}
	      Maximum  number  of repeated occurrences of a regular expression
	      permitted when using the interval notation \{m,n\}; see  Regular
	      Expressions .
	      Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}

   Maximum Values
       The  symbolic constants in the following list shall be defined in <lim‐
       its.h> with the values shown. These are symbolic	 names	for  the  most
       restrictive  value for certain features on an implementation supporting
       the Timers option. A conforming implementation shall provide values  no
       larger  than  these values. A conforming application must not require a
       smaller value for correct operation.

       {_POSIX_CLOCKRES_MIN}

	      The resolution of the CLOCK_REALTIME clock, in nanoseconds.
	      Value: 20 000 000

       If the Monotonic Clock option  is  supported,  the  resolution  of  the
       CLOCK_MONOTONIC clock, in nanoseconds, is represented by {_POSIX_CLOCK‐
       RES_MIN}.

   Minimum Values
       The symbolic constants in the following list shall be defined in	 <lim‐
       its.h>  with  the  values  shown. These are symbolic names for the most
       restrictive value for certain features on an implementation  conforming
       to  this volume of IEEE Std 1003.1-2001. Related symbolic constants are
       defined elsewhere in this volume of IEEE Std 1003.1-2001 which  reflect
       the actual implementation and which need not be as restrictive.	A con‐
       forming implementation shall provide values  at	least  this  large.  A
       strictly	 conforming  application  must	not require a larger value for
       correct operation.

       {_POSIX_AIO_LISTIO_MAX}

	      The number of I/O operations that can be specified in a list I/O
	      call.
	      Value: 2

       {_POSIX_AIO_MAX}

	      The number of outstanding asynchronous I/O operations.
	      Value: 1

       {_POSIX_ARG_MAX}
	      Maximum length of argument to the exec functions including envi‐
	      ronment data.
	      Value: 4 096

       {_POSIX_CHILD_MAX}
	      Maximum number of simultaneous processes per real user ID.
	      Value: 25

       {_POSIX_DELAYTIMER_MAX}

	      The number of timer expiration overruns.
	      Value: 32

       {_POSIX_HOST_NAME_MAX}
	      Maximum length of a host name  (not  including  the  terminating
	      null) as returned from the gethostname() function.
	      Value: 255

       {_POSIX_LINK_MAX}
	      Maximum number of links to a single file.
	      Value: 8

       {_POSIX_LOGIN_NAME_MAX}
	      The  size	 of  the  storage required for a login name, in bytes,
	      including the terminating null.
	      Value: 9

       {_POSIX_MAX_CANON}
	      Maximum number of bytes in a terminal canonical input queue.
	      Value: 255

       {_POSIX_MAX_INPUT}
	      Maximum number of bytes allowed in a terminal input queue.
	      Value: 255

       {_POSIX_MQ_OPEN_MAX}

	      The number of message queues that	 can  be  open	for  a	single
	      process.
	      Value: 8

       {_POSIX_MQ_PRIO_MAX}

	      The maximum number of message priorities supported by the imple‐
	      mentation.
	      Value: 32

       {_POSIX_NAME_MAX}
	      Maximum number of bytes in a filename (not including terminating
	      null).
	      Value: 14

       {_POSIX_NGROUPS_MAX}
	      Maximum  number  of  simultaneous	 supplementary	group  IDs per
	      process.
	      Value: 8

       {_POSIX_OPEN_MAX}
	      Maximum number of files that one process can have	 open  at  any
	      one time.
	      Value: 20

       {_POSIX_PATH_MAX}
	      Maximum number of bytes in a pathname.
	      Value: 256

       {_POSIX_PIPE_BUF}
	      Maximum  number  of  bytes  that is guaranteed to be atomic when
	      writing to a pipe.
	      Value: 512

       {_POSIX_RE_DUP_MAX}
	      The number of repeated occurrences of a  BRE  permitted  by  the
	      regexec()	 and regcomp() functions when using the interval nota‐
	      tion {\(m,n\}; see BREs Matching Multiple Characters .
	      Value: 255

       {_POSIX_RTSIG_MAX}

	      The number of realtime signal numbers reserved  for  application
	      use.
	      Value: 8

       {_POSIX_SEM_NSEMS_MAX}

	      The number of semaphores that a process may have.
	      Value: 256

       {_POSIX_SEM_VALUE_MAX}

	      The maximum value a semaphore may have.
	      Value: 32 767

       {_POSIX_SIGQUEUE_MAX}

	      The  number  of  queued signals that a process may send and have
	      pending at the receiver(s) at any time.
	      Value: 32

       {_POSIX_SSIZE_MAX}
	      The value that can be stored in an object of type ssize_t.
	      Value: 32 767

       {_POSIX_STREAM_MAX}
	      The number of streams that one process  can  have	 open  at  one
	      time.
	      Value: 8

       {_POSIX_SS_REPL_MAX}

	      The  number  of  replenishment operations that may be simultane‐
	      ously pending for a particular sporadic server scheduler.
	      Value: 4

       {_POSIX_SYMLINK_MAX}
	      The number of bytes in a symbolic link.
	      Value: 255

       {_POSIX_SYMLOOP_MAX}
	      The number of symbolic links that can be traversed in the	 reso‐
	      lution of a pathname in the absence of a loop.
	      Value: 8

       {_POSIX_THREAD_DESTRUCTOR_ITERATIONS}

	      The  number  of  attempts made to destroy a thread's thread-spe‐
	      cific data values on thread exit.
	      Value: 4

       {_POSIX_THREAD_KEYS_MAX}

	      The number of data keys per process.
	      Value: 128

       {_POSIX_THREAD_THREADS_MAX}

	      The number of threads per process.
	      Value: 64

       {_POSIX_TIMER_MAX}

	      The per-process number of timers.
	      Value: 32

       {_POSIX_TRACE_EVENT_NAME_MAX}

	      The length in bytes of a trace event name.
	      Value: 30

       {_POSIX_TRACE_NAME_MAX}

	      The length in bytes of a trace generation version	 string	 or  a
	      trace stream name.
	      Value: 8

       {_POSIX_TRACE_SYS_MAX}

	      The number of trace streams that may simultaneously exist in the
	      system.
	      Value: 8

       {_POSIX_TRACE_USER_EVENT_MAX}

	      The number of user trace event type identifiers that may	simul‐
	      taneously	 exist	in  a traced process, including the predefined
	      user trace event POSIX_TRACE_UNNAMED_USER_EVENT.
	      Value: 32

       {_POSIX_TTY_NAME_MAX}
	      The size of the storage required for a terminal device name,  in
	      bytes, including the terminating null.
	      Value: 9

       {_POSIX_TZNAME_MAX}
	      Maximum  number  of  bytes  supported for the name of a timezone
	      (not of the TZ variable).
	      Value: 6

       Note:
	      The length given by {_POSIX_TZNAME_MAX}  does  not  include  the
	      quoting characters mentioned in Other Environment Variables .

       {_POSIX2_BC_BASE_MAX}
	      Maximum obase values allowed by the bc utility.
	      Value: 99

       {_POSIX2_BC_DIM_MAX}
	      Maximum number of elements permitted in an array by the bc util‐
	      ity.
	      Value: 2 048

       {_POSIX2_BC_SCALE_MAX}
	      Maximum scale value allowed by the bc utility.
	      Value: 99

       {_POSIX2_BC_STRING_MAX}
	      Maximum length of a string constant accepted by the bc utility.
	      Value: 1 000

       {_POSIX2_CHARCLASS_NAME_MAX}
	      Maximum number of bytes in a character class name.
	      Value: 14

       {_POSIX2_COLL_WEIGHTS_MAX}
	      Maximum number of weights that can be assigned to	 an  entry  of
	      the  LC_COLLATE order keyword in the locale definition file; see
	      Locale .
	      Value: 2

       {_POSIX2_EXPR_NEST_MAX}
	      Maximum number of expressions that can be nested	within	paren‐
	      theses by the expr utility.
	      Value: 32

       {_POSIX2_LINE_MAX}
	      Unless otherwise noted, the maximum length, in bytes, of a util‐
	      ity's input line (either standard input or another  file),  when
	      the  utility  is	described as processing text files. The length
	      includes room for the trailing <newline>.
	      Value: 2 048

       {_POSIX2_RE_DUP_MAX
	      Maximum number of repeated occurrences of a  regular  expression
	      permitted	 when using the interval notation \{m,n\}; see Regular
	      Expressions .
	      Value: 255

       {_XOPEN_IOV_MAX}

	      Maximum number of iovec structures that one process  has	avail‐
	      able for use with readv() or writev().
	      Value: 16

       {_XOPEN_NAME_MAX}

	      Maximum  number of bytes in a filename (not including the termi‐
	      nating null).
	      Value: 255

       {_XOPEN_PATH_MAX}

	      Maximum number of bytes in a pathname.
	      Value: 1024

   Numerical Limits
       The values in the following lists shall be defined  in  <limits.h>  and
       are  constant  expressions suitable for use in #if preprocessing direc‐
       tives.  Moreover,  except   for	 {CHAR_BIT},   {DBL_DIG},   {DBL_MAX},
       {FLT_DIG},  {FLT_MAX},  {LONG_BIT},  {WORD_BIT},	 and {MB_LEN_MAX}, the
       symbolic names are defined as expressions of the correct type.

       If the value of an object of type char is treated as a  signed  integer
       when used in an expression, the value of {CHAR_MIN} is the same as that
       of {SCHAR_MIN} and the value of {CHAR_MAX}  is  the  same  as  that  of
       {SCHAR_MAX}.  Otherwise,	 the value of {CHAR_MIN} is 0 and the value of
       {CHAR_MAX} is the same as that of {UCHAR_MAX}.

       {CHAR_BIT}
	      Number of bits in a type char.
	      Value: 8

       {CHAR_MAX}
	      Maximum value of type char.
	      Value: {UCHAR_MAX} or {SCHAR_MAX}

       {CHAR_MIN}
	      Minimum value of type char.
	      Value: {SCHAR_MIN} or 0

       {INT_MAX}
	      Maximum value of an int.
	      Minimum Acceptable Value: 2 147 483 647

       {LONG_BIT}

	      Number of bits in a long.
	      Minimum Acceptable Value: 32

       {LONG_MAX}
	      Maximum value of a long.
	      Minimum Acceptable Value: +2 147 483 647

       {MB_LEN_MAX}
	      Maximum number of	 bytes	in  a  character,  for	any  supported
	      locale.
	      Minimum Acceptable Value: 1

       {SCHAR_MAX}
	      Maximum value of type signed char.
	      Value: +127

       {SHRT_MAX}
	      Maximum value of type short.
	      Minimum Acceptable Value: +32 767

       {SSIZE_MAX}
	      Maximum value of an object of type ssize_t.
	      Minimum Acceptable Value: {_POSIX_SSIZE_MAX}

       {UCHAR_MAX}
	      Maximum value of type unsigned char.
	      Value: 255

       {UINT_MAX}
	      Maximum value of type unsigned.
	      Minimum Acceptable Value: 4 294 967 295

       {ULONG_MAX}
	      Maximum value of type unsigned long.
	      Minimum Acceptable Value: 4 294 967 295

       {USHRT_MAX}
	      Maximum value for a type unsigned short.
	      Minimum Acceptable Value: 65 535

       {WORD_BIT}

	      Number of bits in a word or type int.
	      Minimum Acceptable Value: 16

       {INT_MIN}
	      Minimum value of type int.
	      Maximum Acceptable Value: -2 147 483 647

       {LONG_MIN}
	      Minimum value of type long.
	      Maximum Acceptable Value: -2 147 483 647

       {SCHAR_MIN}
	      Minimum value of type signed char.
	      Value: -128

       {SHRT_MIN}
	      Minimum value of type short.
	      Maximum Acceptable Value: -32 767

       {LLONG_MIN}
	      Minimum value of type long long.
	      Maximum Acceptable Value: -9223372036854775807

       {LLONG_MAX}
	      Maximum value of type long long.
	      Minimum Acceptable Value: +9223372036854775807

       {ULLONG_MAX}
	      Maximum value of type unsigned long long.
	      Minimum Acceptable Value: 18446744073709551615

   Other Invariant Values
       The  following  constants  shall	 be  defined on all implementations in
       <limits.h>:

       {CHARCLASS_NAME_MAX}

	      Maximum number of bytes in a character class name.
	      Minimum Acceptable Value: 14

       {NL_ARGMAX}

	      Maximum value of digit in calls  to  the	printf()  and  scanf()
	      functions.
	      Minimum Acceptable Value: 9

       {NL_LANGMAX}

	      Maximum number of bytes in a LANG name.
	      Minimum Acceptable Value: 14

       {NL_MSGMAX}

	      Maximum message number.
	      Minimum Acceptable Value: 32 767

       {NL_NMAX}

	      Maximum number of bytes in an N-to-1 collation mapping.
	      Minimum  Acceptable  Value:  No guaranteed value across all con‐
	      forming implementations.

       {NL_SETMAX}

	      Maximum set number.
	      Minimum Acceptable Value: 255

       {NL_TEXTMAX}

	      Maximum number of bytes in a message string.
	      Minimum Acceptable Value: {_POSIX2_LINE_MAX}

       {NZERO}

	      Default process priority.
	      Minimum Acceptable Value: 20

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       A request was made to reduce the value of  {_POSIX_LINK_MAX}  from  the
       value  of  8  specified	for  it in the POSIX.1-1990 standard to 2. The
       standard developers decided to deny this request for several reasons:

	* They wanted to avoid making any changes to the standard  that	 could
	  break	 conforming  applications, and the requested change could have
	  that effect.

	* The use of multiple hard links to a file cannot always  be  replaced
	  with	use of symbolic links. Symbolic links are semantically differ‐
	  ent from hard links in that they associate a pathname	 with  another
	  pathname  rather  than a pathname with a file. This has implications
	  for access control, file permanence, and transparency.

	* The original standard developers had considered the issue of	allow‐
	  ing  for implementations that did not in general support hard links,
	  and decided that this would reduce consensus on the standard.

       Systems that support historical versions of the development  option  of
       the  ISO POSIX-2	 standard  retain  the name {_POSIX2_RE_DUP_MAX} as an
       alias for {_POSIX_RE_DUP_MAX}.

       {PATH_MAX}
	      IEEE PASC Interpretation 1003.1 #15 addressed the	 inconsistency
	      in the standard with the definition of pathname and the descrip‐
	      tion of {PATH_MAX}, allowing  application	 writers  to  allocate
	      either  {PATH_MAX}  or {PATH_MAX}+1 bytes. The inconsistency has
	      been removed by  correction  to  the  {PATH_MAX}	definition  to
	      include the null character.  With this change, applications that
	      previously allocated {PATH_MAX} bytes will continue to succeed.

       {SYMLINK_MAX}
	      This symbol refers to space for data that is stored in the  file
	      system,  as  opposed to {PATH_MAX} which is the length of a name
	      that can be passed to a function. In some	 existing  implementa‐
	      tions,  the filenames pointed to by symbolic links are stored in
	      the inodes of the links, so it is important  that	 {SYMLINK_MAX}
	      not be constrained to be as large as {PATH_MAX}.

FUTURE DIRECTIONS
       None.

SEE ALSO
       The  System  Interfaces	volume	of  IEEE Std 1003.1-2001, fpathconf(),
       pathconf(), sysconf()

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  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.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			<limits.h>(0P)
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