limits.h(3)                POSIX Programmer's Manual               limits.h(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.


NNAAMMEE
       limits.h -- implementation-defined constants

SSYYNNOOPPSSIISS
       #include <limits.h>

DDEESSCCRRIIPPTTIIOONN
       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, _S_e_c_t_i_o_n _2_._2,
       _T_h_e _C_o_m_p_i_l_a_t_i_o_n _E_n_v_i_r_o_n_m_e_n_t) 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 _<_l_i_m_i_t_s_._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 ##iiff 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 _<_u_n_i_s_t_d_._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
       _<_l_i_m_i_t_s_._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 _f_p_a_t_h_c_o_n_f(), _p_a_t_h_c_o_n_f(),
       and _s_y_s_c_o_n_f() 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 _<_l_i_m_i_t_s_._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.

   RRuunnttiimmee IInnvvaarriiaanntt VVaalluueess ((PPoossssiibbllyy IInnddeetteerrmmiinnaattee))
       A definition of one of the symbolic constants in the following list
       shall be omitted from _<_l_i_m_i_t_s_._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
       _s_y_s_c_o_n_f() 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 _e_x_e_c functions including
             environment data.
             Minimum Acceptable Value: {_POSIX_ARG_MAX}

       {ATEXIT_MAX}
             Maximum number of functions that may be registered with _a_t_e_x_i_t().
             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 _g_e_t_h_o_s_t_n_a_m_e() function.
             Minimum Acceptable Value: {_POSIX_HOST_NAME_MAX}

       {IOV_MAX}
             Maximum number of iioovveecc structures that one process has available
             for use with _r_e_a_d_v() or _w_r_i_t_e_v().
             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 _S_e_c_t_i_o_n _9_._3_._6, _B_R_E_s _M_a_t_c_h_i_n_g _M_u_l_t_i_p_l_e _C_h_a_r_a_c_t_e_r_s
             and _S_e_c_t_i_o_n _9_._4_._6, _E_R_E_s _M_a_t_c_h_i_n_g _M_u_l_t_i_p_l_e _C_h_a_r_a_c_t_e_r_s.
             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
             _<_s_t_d_i_o_._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 _T_Z variable).
             Minimum Acceptable Value: {_POSIX_TZNAME_MAX}

       NNoottee::     The length given by {TZNAME_MAX} does not include the quoting
                 characters mentioned in _S_e_c_t_i_o_n _8_._3, _O_t_h_e_r _E_n_v_i_r_o_n_m_e_n_t
                 _V_a_r_i_a_b_l_e_s.

   PPaatthhnnaammee VVaarriiaabbllee VVaalluueess
       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 _<_l_i_m_i_t_s_._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 _p_a_t_h_c_o_n_f() 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}

   RRuunnttiimmee IInnccrreeaassaabbllee VVaalluueess
       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 _<_l_i_m_i_t_s_._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
       _<_l_i_m_i_t_s_._h_> for that implementation. The actual value supported by a
       specific instance shall be provided by the _s_y_s_c_o_n_f() function.

       {BC_BASE_MAX}
             Maximum _o_b_a_s_e values allowed by the _b_c utility.
             Minimum Acceptable Value: {_POSIX2_BC_BASE_MAX}

       {BC_DIM_MAX}
             Maximum number of elements permitted in an array by the _b_c
             utility.
             Minimum Acceptable Value: {_POSIX2_BC_DIM_MAX}

       {BC_SCALE_MAX}
             Maximum _s_c_a_l_e value allowed by the _b_c utility.
             Minimum Acceptable Value: {_POSIX2_BC_SCALE_MAX}

       {BC_STRING_MAX}
             Maximum length of a string constant accepted by the _b_c 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
             _L_C___C_O_L_L_A_T_E oorrddeerr keyword in the locale definition file; see
             _C_h_a_p_t_e_r _7, _L_o_c_a_l_e.
             Minimum Acceptable Value: {_POSIX2_COLL_WEIGHTS_MAX}

       {EXPR_NEST_MAX}
             Maximum number of expressions that can be nested within
             parentheses by the _e_x_p_r 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 _C_h_a_p_t_e_r
             _9, _R_e_g_u_l_a_r _E_x_p_r_e_s_s_i_o_n_s.
             Minimum Acceptable Value: {_POSIX2_RE_DUP_MAX}

   MMaaxxiimmuumm VVaalluueess
       The _<_l_i_m_i_t_s_._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}.

   MMiinniimmuumm VVaalluueess
       The _<_l_i_m_i_t_s_._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 _e_x_e_c 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 _g_e_t_h_o_s_t_n_a_m_e() 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
             _r_e_g_e_x_e_c() and _r_e_g_c_o_m_p() functions when using the interval
             notation {\(_m,_n\}; see _S_e_c_t_i_o_n _9_._3_._6, _B_R_E_s _M_a_t_c_h_i_n_g _M_u_l_t_i_p_l_e
             _C_h_a_r_a_c_t_e_r_s.
             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 ssssiizzee__tt.
             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 _T_Z variable).
             Value: 6

             NNoottee::     The length given by {_POSIX_TZNAME_MAX} does not
                       include the quoting characters mentioned in _S_e_c_t_i_o_n
                       _8_._3, _O_t_h_e_r _E_n_v_i_r_o_n_m_e_n_t _V_a_r_i_a_b_l_e_s.

       {_POSIX2_BC_BASE_MAX}
             Maximum _o_b_a_s_e values allowed by the _b_c utility.
             Value: 99

       {_POSIX2_BC_DIM_MAX}
             Maximum number of elements permitted in an array by the _b_c
             utility.
             Value: 2 048

       {_POSIX2_BC_SCALE_MAX}
             Maximum _s_c_a_l_e value allowed by the _b_c utility.
             Value: 99

       {_POSIX2_BC_STRING_MAX}
             Maximum length of a string constant accepted by the _b_c 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
             _L_C___C_O_L_L_A_T_E oorrddeerr keyword in the locale definition file; see
             _C_h_a_p_t_e_r _7, _L_o_c_a_l_e.
             Value: 2

       {_POSIX2_EXPR_NEST_MAX}
             Maximum number of expressions that can be nested within
             parentheses by the _e_x_p_r 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 _C_h_a_p_t_e_r
             _9, _R_e_g_u_l_a_r _E_x_p_r_e_s_s_i_o_n_s.
             Value: 255

       {_XOPEN_IOV_MAX}
             Maximum number of iioovveecc structures that one process has available
             for use with _r_e_a_d_v() or _w_r_i_t_e_v().
             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

   NNuummeerriiccaall LLiimmiittss
       The _<_l_i_m_i_t_s_._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 cchhaarr 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 cchhaarr.
             Value: 8

       {CHAR_MAX}
             Maximum value for an object of type cchhaarr.
             Value: {UCHAR_MAX} or {SCHAR_MAX}

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

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

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

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

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

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

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

       {LONG_MIN}
             Minimum value for an object of type lloonngg.
             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 ssiiggnneedd cchhaarr.
             Value: +127

       {SCHAR_MIN}
             Minimum value for an object of type ssiiggnneedd cchhaarr.
             Value: -128

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

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

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

       {UCHAR_MAX}
             Maximum value for an object of type uunnssiiggnneedd cchhaarr.
             Value: 255

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

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

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

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

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

   OOtthheerr IInnvvaarriiaanntt VVaalluueess
       The _<_l_i_m_i_t_s_._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 _p_r_i_n_t_f() and _s_c_a_n_f() families of
             functions.
             Minimum Acceptable Value: 9

       {NL_LANGMAX}
             Maximum number of bytes in a _L_A_N_G 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

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       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 _i_n_o_d_es of the links, so it is important that
             {SYMLINK_MAX} not be constrained to be as large as {PATH_MAX}.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _C_h_a_p_t_e_r _7, _L_o_c_a_l_e, <<ssttddiioo..hh>>, <<uunniissttdd..hh>>

       The System Interfaces volume of POSIX.1-2008, _S_e_c_t_i_o_n _2_._2, _T_h_e
       _C_o_m_p_i_l_a_t_i_o_n _E_n_v_i_r_o_n_m_e_n_t, _f_p_a_t_h_c_o_n_f(), _s_y_s_c_o_n_f()

CCOOPPYYRRIIGGHHTT
       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 .



IEEE/The Open Group                  2013                          limits.h(3)
