277 lines
8.7 KiB
Groff
277 lines
8.7 KiB
Groff
.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd February 13, 2011
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.Dt SYSCONF 3
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.Os
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.Sh NAME
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.Nm sysconf
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.Nd get configurable system variables
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft long
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.Fn sysconf "int name"
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.Sh DESCRIPTION
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This interface is defined by
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.St -p1003.1-88 .
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A far more complete interface is available using
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.Xr sysctl 3 .
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.Pp
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The
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.Fn sysconf
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function provides a method for applications to determine the current
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value of a configurable system limit or option variable.
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The
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.Fa name
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argument specifies the system variable to be queried.
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Symbolic constants for each name value are found in the include file
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.In unistd.h .
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Shell programmers who need access to these parameters should use the
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.Xr getconf 1
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utility.
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.Pp
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The available values are as follows:
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.Bl -tag -width 6n
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.It Li _SC_ARG_MAX
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The maximum bytes of argument to
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.Xr execve 2 .
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.It Li _SC_CHILD_MAX
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The maximum number of simultaneous processes per user id.
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.It Li _SC_CLK_TCK
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The frequency of the statistics clock in ticks per second.
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.It Li _SC_IOV_MAX
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The maximum number of elements in the I/O vector used by
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.Xr readv 2 ,
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.Xr writev 2 ,
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.Xr recvmsg 2 ,
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and
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.Xr sendmsg 2 .
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.It Li _SC_NGROUPS_MAX
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The maximum number of supplemental groups.
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.It Li _SC_NPROCESSORS_CONF
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The number of processors configured.
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.It Li _SC_NPROCESSORS_ONLN
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The number of processors currently online.
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.It Li _SC_OPEN_MAX
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The maximum number of open files per user id.
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.It Li _SC_PAGESIZE
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The size of a system page in bytes.
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.It Li _SC_PAGE_SIZE
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Equivalent to
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.Li _SC_PAGESIZE .
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.It Li _SC_STREAM_MAX
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The minimum maximum number of streams that a process may have open
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at any one time.
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.It Li _SC_TZNAME_MAX
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The minimum maximum number of types supported for the name of a
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timezone.
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.It Li _SC_JOB_CONTROL
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Return 1 if job control is available on this system, otherwise \-1.
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.It Li _SC_SAVED_IDS
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Returns 1 if saved set-group and saved set-user ID is available,
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otherwise \-1.
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.It Li _SC_VERSION
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The version of
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.St -p1003.1
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with which the system
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attempts to comply.
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.It Li _SC_BC_BASE_MAX
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The maximum ibase/obase values in the
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.Xr bc 1
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utility.
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.It Li _SC_BC_DIM_MAX
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The maximum array size in the
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.Xr bc 1
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utility.
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.It Li _SC_BC_SCALE_MAX
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The maximum scale value in the
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.Xr bc 1
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utility.
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.It Li _SC_BC_STRING_MAX
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The maximum string length in the
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.Xr bc 1
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utility.
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.It Li _SC_COLL_WEIGHTS_MAX
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The maximum number of weights that can be assigned to any entry of
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the LC_COLLATE order keyword in the locale definition file.
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.It Li _SC_EXPR_NEST_MAX
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The maximum number of expressions that can be nested within
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parenthesis by the
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.Xr expr 1
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utility.
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.It Li _SC_LINE_MAX
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The maximum length in bytes of a text-processing utility's input
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line.
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.It Li _SC_RE_DUP_MAX
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The maximum number of repeated occurrences of a regular expression
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permitted when using interval notation.
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.It Li _SC_2_VERSION
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The version of
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.St -p1003.2
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with which the system attempts to comply.
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.It Li _SC_2_C_BIND
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Return 1 if the system's C-language development facilities support the
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C-Language Bindings Option, otherwise \-1.
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.It Li _SC_2_C_DEV
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Return 1 if the system supports the C-Language Development Utilities Option,
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otherwise \-1.
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.It Li _SC_2_CHAR_TERM
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Return 1 if the system supports at least one terminal type capable of
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all operations described in
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.St -p1003.2 ,
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otherwise \-1.
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.It Li _SC_2_FORT_DEV
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Return 1 if the system supports the FORTRAN Development Utilities Option,
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otherwise \-1.
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.It Li _SC_2_FORT_RUN
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Return 1 if the system supports the FORTRAN Runtime Utilities Option,
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otherwise \-1.
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.It Li _SC_2_LOCALEDEF
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Return 1 if the system supports the creation of locales, otherwise \-1.
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.It Li _SC_2_SW_DEV
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Return 1 if the system supports the Software Development Utilities Option,
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otherwise \-1.
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.It Li _SC_2_UPE
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Return 1 if the system supports the User Portability Utilities Option,
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otherwise \-1.
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.It Li _SC_AIO_LISTIO_MAX
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Maximum number of I/O operations in a single list I/O call supported.
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.It Li _SC_AIO_MAX
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Maximum number of outstanding asynchronous I/O operations supported.
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.It Li _SC_AIO_PRIO_DELTA_MAX
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The maximum amount by which a process can decrease its asynchronous I/O
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priority level from its own scheduling priority.
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.It Li _SC_DELAYTIMER_MAX
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Maximum number of timer expiration overruns.
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.It Li _SC_MQ_OPEN_MAX
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The maximum number of open message queue descriptors a process may hold.
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.It Li _SC_RTSIG_MAX
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Maximum number of realtime signals reserved for application use.
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.It Li _SC_SEM_NSEMS_MAX
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Maximum number of semaphores that a process may have.
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.It Li _SC_SEM_VALUE_MAX
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The maximum value a semaphore may have.
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.It Li _SC_SIGQUEUE_MAX
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Maximum number of queued signals that a process may send and have pending at
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the receiver(s) at any time.
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.It Li _SC_TIMER_MAX
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Maximum number of timers per process supported.
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.It Li _SC_GETGR_R_SIZE_MAX
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Suggested initial value for the size of the group entry buffer.
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.It Li _SC_GETPW_R_SIZE_MAX
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Suggested initial value for the size of the password entry buffer.
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.It Li _SC_HOST_NAME_MAX
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Maximum length of a host name (not including the terminating null) as
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returned from the
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.Fn gethostname
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function.
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.It Li _SC_LOGIN_NAME_MAX
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Maximum length of a login name.
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.It Li _SC_THREAD_STACK_MIN
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Minimum size in bytes of thread stack storage.
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.It Li _SC_THREAD_THREADS_MAX
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Maximum number of threads that can be created per process.
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.It Li _SC_TTY_NAME_MAX
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Maximum length of terminal device name.
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.It Li _SC_SYMLOOP_MAX
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Maximum number of symbolic links that can be reliably traversed in the
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resolution of a pathname in the absence of a loop.
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.It Li _SC_ATEXIT_MAX
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Maximum number of functions that may be registered with
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.Fn atexit .
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.It Li _SC_XOPEN_VERSION
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An integer value greater than or equal to 4,
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indicating the version of the X/Open Portability Guide to which this
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system conforms.
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.It Li _SC_XOPEN_XCU_VERSION
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An integer value indicating the version of the XCU Specification to which
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this system conforms.
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.El
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.Pp
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These values also exist, but may not be standard:
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.Bl -tag -width 6n
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.It Li _SC_CPUSET_SIZE
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Size of the kernel cpuset.
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.It Li _SC_PHYS_PAGES
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The number of pages of physical memory.
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Note that it is possible that the product of this value and the value of
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.Li _SC_PAGESIZE
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will overflow a
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.Vt long
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in some configurations on a 32bit machine.
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.El
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.Sh RETURN VALUES
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If the call to
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.Fn sysconf
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is not successful, \-1 is returned and
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.Va errno
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is set appropriately.
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Otherwise, if the variable is associated with functionality that is not
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supported, \-1 is returned and
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.Va errno
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is not modified.
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Otherwise, the current variable value is returned.
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.Sh ERRORS
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The
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.Fn sysconf
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function may fail and set
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.Va errno
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for any of the errors specified for the library function
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.Xr sysctl 3 .
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In addition, the following error may be reported:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value of the
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.Fa name
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argument is invalid.
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.El
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.Sh SEE ALSO
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.Xr getconf 1 ,
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.Xr pathconf 2 ,
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.Xr confstr 3 ,
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.Xr sysctl 3
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.Sh STANDARDS
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Except for the fact that values returned by
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.Fn sysconf
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may change over the lifetime of the calling process,
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this function conforms to
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.St -p1003.1-88 .
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.Sh HISTORY
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The
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.Fn sysconf
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function first appeared in
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.Bx 4.4 .
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.Sh BUGS
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The value for _SC_STREAM_MAX is a minimum maximum, and required to be
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the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
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small and misleading number.
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