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

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 asyn-
              chronous 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
              implementation.
              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  pro-
              cess.
              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  pro-
              cess.
              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 pro-
              cess.
              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>(P)

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