Provided by: manpages-posix-dev_2013a-1_all bug

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, provided 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  <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  implementations,  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  supported  by  the
             implementation.
             Minimum Acceptable Value: {_POSIX_AIO_LISTIO_MAX}

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

       {AIO_PRIO_DELTA_MAX}
             The maximum amount by which a process can decrease  its  asynchronous  I/O  priority
             level from its own scheduling priority.
             Minimum Acceptable Value: 0

       {ARG_MAX}
             Maximum length of argument to the exec functions including environment 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 implementation.
             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-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}
             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  simultaneously  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 implementation.
             Minimum Acceptable Value: {_POSIX_TIMER_MAX}

       {TRACE_EVENT_NAME_MAX}
             Maximum length of the trace event name (not including the terminating 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    predefined    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 Variables.

   Pathname Variable Values
       The values in the following list may be constants within an  implementation  or  may  vary
       from  one pathname to another. For example, file systems 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 specified 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 terminal input queue;
             therefore, the maximum number of bytes a conforming 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 the terminating 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  pathname  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   specific
       implementations.  An  application  should  assume  that the value of the symbolic constant
       defined 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 utility.
             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 Chapter 7, Locale.
             Minimum Acceptable Value: {_POSIX2_COLL_WEIGHTS_MAX}

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

       {LINE_MAX}
             Unless otherwise noted, the maximum length, in bytes,  of  a  utility'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  certain  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 certain 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 conforming 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 environment 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 implementation.
             Value: 32

       {_POSIX_NAME_MAX}
             Maximum  number  of  bytes  in  a  filename (not including the terminating 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 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  notation  {\(m,n\};  see  Section 9.3.6, 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_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 resolution 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 terminating 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 simultaneously 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 utility.
             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 Chapter 7, Locale.
             Value: 2

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

       {_POSIX2_LINE_MAX}
             Unless otherwise noted, the maximum length, in bytes,  of  a  utility'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  terminating  null  of  a
             filename string).
             Value: 255

       {_XOPEN_PATH_MAX}
             Minimum  number  the  implementation will accept as the maximum number 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 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_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 different 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  allowing  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 description 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 implementations, 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 Compilation 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  Electrical  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.kernel.org/doc/man-pages/reporting_bugs.html .