222 lines
7.2 KiB
Groff
222 lines
7.2 KiB
Groff
.\" $OpenBSD: sysconf.3,v 1.35 2019/08/11 15:48:08 deraadt Exp $
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.\"
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.\" 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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.\" 3. 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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.Dd $Mdocdate: August 11 2019 $
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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 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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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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.Pp
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The available values are as follows:
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.Bl -tag -width "123456"
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.It Li _SC_ARG_MAX
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The maximum bytes of arguments to
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.Xr execve 2
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(including the environment).
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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 number of clock ticks per second.
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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_OPEN_MAX
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The maximum number of open files per user ID.
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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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time zone.
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.It Li _SC_JOB_CONTROL
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Returns 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-ID 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 ISO/IEC 9945 (POSIX 1003.1) 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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parentheses 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 POSIX 1003.2 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 POSIX 1003.2, 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_PAGESIZE
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The size of a system page in bytes.
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.It Li _SC_FSYNC
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Return 1 if the system supports the File Synchronisation Option, otherwise \-1.
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.It Li _SC_XOPEN_SHM
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Return 1 if the system supports the Shared Memory Option, otherwise \-1.
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.It Li _SC_SEM_NSEMS_MAX
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The maximum number of semaphores in the system or \-1 if the system
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does not support the Semaphores Option.
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.It Li _SC_SEM_VALUE_MAX
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The maximum value a semaphore may have or \-1 if the system
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does not support the Semaphores Option.
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.It Li _SC_PHYS_PAGES
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The number of pages of physical memory.
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.It Li _SC_AVPHYS_PAGES
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The number of pages of physical memory not currently in use by the system.
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.It Li _SC_GETGR_R_SIZE_MAX
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The maximum size of the data buffer for the
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.Fn getgrgid_r
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and
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.Fn getgrnam_r
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functions.
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.It Li _SC_GETPW_R_SIZE_MAX
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The maximum size of the data buffer for the
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.Fn getpwuid_r
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and
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.Fn getpwnam_r
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functions.
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.It Li _SC_LOGIN_NAME_MAX
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The maximum length of a login name.
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.It Li _SC_THREAD_SAFE_FUNCTIONS
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The level of support for thread-safe (re-entrant) functions.
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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 online (capable of running processes).
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.It Li _SC_HOST_NAME_MAX
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The maximum size of a hostname, not counting NULL.
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.It Li _SC_MONOTONIC_CLOCK
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Return the POSIX version of the implementation of the Monotonic Clock
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option that this system conforms to, or \-1 if unavailable.
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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 2 .
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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 pathconf 2 ,
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.Xr sysctl 2
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.Sh STANDARDS
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The
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.Fn sysconf
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function conforms to
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.St -p1003.1-88 .
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The constants
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.Li _SC_NPROCESSORS_CONF
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and
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.Li _SC_NPROCESSORS_ONLN
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are not part of the standard, but are provided by many systems.
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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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