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

PROLOG
       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
       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 POSIX.1‐2008,	 Section  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,
       except under the heading ``Numerical Limits''.

       The <limits.h> header shall define macros and  symbolic	constants  for
       various	limits.	  Different  categories of limits are described below,
       representing  various  limits  on  resources  that  the	implementation
       imposes	on applications.  All macros and symbolic constants defined in
       this header shall be suitable for use in #if preprocessing directives.

       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 appli‐
       cation wishing to avail itself of the full amount of a resource	avail‐
       able on an implementation may make use of the value given in <limits.h>
       on that particular implementation, by using  the	 macros	 and  symbolic
       constants  listed  below. It should be noted, however, that many of the
       listed limits are not invariant, and at runtime, the value of the limit
       may differ 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 constants in the following list
       shall be omitted from <limits.h> on specific implementations where  the
       corresponding 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 available
	     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}
	     A	value  one  greater than the maximum value that the system may
	     assign to a newly-created file descriptor.
	     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-spe‐
	     cific 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}
	     Maximum number of repeated occurrences of a BRE or	 ERE  interval
	     expression;  see Section 9.3.6, BREs Matching Multiple Characters
	     and Section 9.4.6, EREs 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 simul‐
	     taneously pending for a particular sporadic server scheduler.
	     Minimum Acceptable Value: {_POSIX_SS_REPL_MAX}

       {STREAM_MAX}
	     Maximum  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 implementa‐
	     tion.
	     Minimum Acceptable Value: {_POSIX_TIMER_MAX}

       {TRACE_EVENT_NAME_MAX}
	     Maximum  length of the trace event name (not including the termi‐
	     nating null).
	     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 (not including the terminating null).
	     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 Section 8.3, Other Environment	 Vari‐
		 ables.

   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 symbolic constants in the following list
       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 read‐
	     ing them.
	     Minimum Acceptable Value: {_POSIX_MAX_INPUT}

       {NAME_MAX}
	     Maximum  number  of bytes in a filename (not including the termi‐
	     nating null of a filename string).
	     Minimum Acceptable Value: {_POSIX_NAME_MAX}
	     Minimum Acceptable Value: {_XOPEN_NAME_MAX}

       {PATH_MAX}
	     Maximum number of bytes the implementation will store as a	 path‐
	     name in a user-supplied buffer of unspecified size, including the
	     terminating null character.  Minimum  number  the	implementation
	     will accept as the maximum number of bytes in a pathname.
	     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 of
       the symbolic constant defined by <limits.h> in a	 specific  implementa‐
       tion 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 Chap‐
	     ter 7, Locale.
	     Minimum Acceptable Value: {_POSIX2_COLL_WEIGHTS_MAX}

       {EXPR_NEST_MAX}
	     Maximum number of expressions that can be nested within parenthe‐
	     ses 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  Chapter
	     9, Regular Expressions.
	     Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}

   Maximum Values
       The  <limits.h>	header	shall  define the following symbolic constants
       with the values shown. These are the most restrictive values  for  cer‐
       tain  features  on an implementation. 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_CLOCKRES_MIN}.

   Minimum Values
       The  <limits.h>	header	shall  define the following symbolic constants
       with the values shown. These are the most restrictive values  for  cer‐
       tain  features  on  an  implementation  conforming  to  this  volume of
       POSIX.1‐2008. Related symbolic constants are defined elsewhere in  this
       volume  of  POSIX.1‐2008	 which	reflect	 the actual implementation and
       which need not be as restrictive. For each of these limits, a  conform‐
       ing  implementation  shall provide a value at least this large or shall
       have no limit. 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 the termi‐
	     nating null of a filename string).
	     Value: 14

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

       {_POSIX_OPEN_MAX}
	     A	value  one  greater than the maximum value that the system may
	     assign to a newly-created file descriptor.
	     Value: 20

       {_POSIX_PATH_MAX}
	     Minimum number the implementation will accept as the maximum num‐
	     ber 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 Section 9.3.6, BREs Matching Multiple  Charac‐
	     ters.
	     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_SS_REPL_MAX}
	     The number of replenishment operations that may be simultaneously
	     pending for a particular sporadic server scheduler.
	     Value: 4

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

       {_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 resolu‐
	     tion 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-specific
	     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 (not including the ter‐
	     minating null).
	     Value: 30

       {_POSIX_TRACE_NAME_MAX}
	     The  length  in  bytes  of a trace generation version string or a
	     trace stream name (not including the terminating null).
	     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 simulta‐
	     neously 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  Section
		       8.3, 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 Chap‐
	     ter 7, Locale.
	     Value: 2

       {_POSIX2_EXPR_NEST_MAX}
	     Maximum number of expressions that can be nested within parenthe‐
	     ses 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 Chapter
	     9, Regular Expressions.
	     Value: 255

       {_XOPEN_IOV_MAX}
	     Maximum number of iovec structures that one process has available
	     for use with readv() or writev().
	     Value: 16

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

       {_XOPEN_PATH_MAX}
	     Minimum number the implementation will accept as the maximum num‐
	     ber of bytes in a pathname.
	     Value: 1024

   Numerical Limits
       The <limits.h> header shall define the following macros and, except for
       {CHAR_BIT}, {LONG_BIT}, {MB_LEN_MAX}, and  {WORD_BIT},  they  shall  be
       replaced	 by expressions that have the same type as would an expression
       that is an object of the corresponding type converted according to  the
       integer promotions.

       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 for an object of type char.
	     Value: {UCHAR_MAX} or {SCHAR_MAX}

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

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

       {INT_MIN}
	     Minimum value for an object of type int.
	     Maximum Acceptable Value: −2 147 483 647

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

       {LLONG_MIN}
	     Minimum value for an object of type long long.
	     Maximum Acceptable Value: −9223372036854775807

       {LONG_BIT}
	     Number of bits in an object of type long.
	     Minimum Acceptable Value: 32

       {LONG_MAX}
	     Maximum value for an object of type long.
	     Minimum Acceptable Value: +2 147 483 647

       {LONG_MIN}
	     Minimum value for an object of type long.
	     Maximum 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 for an object of type signed char.
	     Value: +127

       {SCHAR_MIN}
	     Minimum value for an object of type signed char.
	     Value: −128

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

       {SHRT_MIN}
	     Minimum value for an object of type short.
	     Maximum Acceptable Value: −32 767

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

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

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

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

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

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

       {WORD_BIT}
	     Number of bits in an object of type int.
	     Minimum Acceptable Value: 32

   Other Invariant Values
       The <limits.h> header shall define the following symbolic constants:

       {NL_ARGMAX}
	     Maximum  value  of n in conversion specifications using the "%n$"
	     sequence in calls to the printf() and scanf() families  of	 func‐
	     tions.
	     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_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 developers 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 pathnames 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
       Chapter 7, Locale, <stdio.h>, <unistd.h>

       The System Interfaces volume of POSIX.1‐2008, Section 2.2, The Compila‐
       tion Environment, fpathconf(), sysconf()

COPYRIGHT
       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 Electri‐
       cal  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 .

       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,	 see  https://www.ker‐
       nel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2013			  limits.h(0P)
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