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+.\" Copyright (c) 1993
+.\" The Regents of the University of California. All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94
+.\" $FreeBSD$
+.\"
+.Dd June 18, 2001
+.Dt SYSCONF 3
+.Os
+.Sh NAME
+.Nm sysconf
+.Nd get configurable system variables
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In unistd.h
+.Ft long
+.Fn sysconf "int name"
+.Sh DESCRIPTION
+This interface is defined by
+.St -p1003.1-88 .
+A far more complete interface is available using
+.Xr sysctl 3 .
+.Pp
+The
+.Fn sysconf
+function provides a method for applications to determine the current
+value of a configurable system limit or option variable.
+The
+.Fa name
+argument specifies the system variable to be queried.
+Symbolic constants for each name value are found in the include file
+.In unistd.h .
+Shell programmers who need access to these parameters should use the
+.Xr getconf 1
+utility.
+.Pp
+The available values are as follows:
+.Pp
+.Bl -tag -width 6n
+.Pp
+.It Li _SC_ARG_MAX
+The maximum bytes of argument to
+.Xr execve 2 .
+.It Li _SC_CHILD_MAX
+The maximum number of simultaneous processes per user id.
+.It Li _SC_CLK_TCK
+The frequency of the statistics clock in ticks per second.
+.It Li _SC_IOV_MAX
+The maximum number of elements in the I/O vector used by
+.Xr readv 2 ,
+.Xr writev 2 ,
+.Xr recvmsg 2 ,
+and
+.Xr sendmsg 2 .
+.It Li _SC_NGROUPS_MAX
+The maximum number of supplemental groups.
+.It Li _SC_NPROCESSORS_CONF
+The number of processors configured.
+.It Li _SC_NPROCESSORS_ONLN
+The number of processors currently online.
+.It Li _SC_OPEN_MAX
+The maximum number of open files per user id.
+.It Li _SC_STREAM_MAX
+The minimum maximum number of streams that a process may have open
+at any one time.
+.It Li _SC_TZNAME_MAX
+The minimum maximum number of types supported for the name of a
+timezone.
+.It Li _SC_JOB_CONTROL
+Return 1 if job control is available on this system, otherwise \-1.
+.It Li _SC_SAVED_IDS
+Returns 1 if saved set-group and saved set-user ID is available,
+otherwise \-1.
+.It Li _SC_VERSION
+The version of
+.St -p1003.1
+with which the system
+attempts to comply.
+.It Li _SC_BC_BASE_MAX
+The maximum ibase/obase values in the
+.Xr bc 1
+utility.
+.It Li _SC_BC_DIM_MAX
+The maximum array size in the
+.Xr bc 1
+utility.
+.It Li _SC_BC_SCALE_MAX
+The maximum scale value in the
+.Xr bc 1
+utility.
+.It Li _SC_BC_STRING_MAX
+The maximum string length in the
+.Xr bc 1
+utility.
+.It Li _SC_COLL_WEIGHTS_MAX
+The maximum number of weights that can be assigned to any entry of
+the LC_COLLATE order keyword in the locale definition file.
+.It Li _SC_EXPR_NEST_MAX
+The maximum number of expressions that can be nested within
+parenthesis by the
+.Xr expr 1
+utility.
+.It Li _SC_LINE_MAX
+The maximum length in bytes of a text-processing utility's input
+line.
+.It Li _SC_RE_DUP_MAX
+The maximum number of repeated occurrences of a regular expression
+permitted when using interval notation.
+.It Li _SC_2_VERSION
+The version of
+.St -p1003.2
+with which the system attempts to comply.
+.It Li _SC_2_C_BIND
+Return 1 if the system's C-language development facilities support the
+C-Language Bindings Option, otherwise \-1.
+.It Li _SC_2_C_DEV
+Return 1 if the system supports the C-Language Development Utilities Option,
+otherwise \-1.
+.It Li _SC_2_CHAR_TERM
+Return 1 if the system supports at least one terminal type capable of
+all operations described in
+.St -p1003.2 ,
+otherwise \-1.
+.It Li _SC_2_FORT_DEV
+Return 1 if the system supports the FORTRAN Development Utilities Option,
+otherwise \-1.
+.It Li _SC_2_FORT_RUN
+Return 1 if the system supports the FORTRAN Runtime Utilities Option,
+otherwise \-1.
+.It Li _SC_2_LOCALEDEF
+Return 1 if the system supports the creation of locales, otherwise \-1.
+.It Li _SC_2_SW_DEV
+Return 1 if the system supports the Software Development Utilities Option,
+otherwise \-1.
+.It Li _SC_2_UPE
+Return 1 if the system supports the User Portability Utilities Option,
+otherwise \-1.
+.El
+.Sh RETURN VALUES
+If the call to
+.Fn sysconf
+is not successful, \-1 is returned and
+.Va errno
+is set appropriately.
+Otherwise, if the variable is associated with functionality that is not
+supported, \-1 is returned and
+.Va errno
+is not modified.
+Otherwise, the current variable value is returned.
+.Sh ERRORS
+The
+.Fn sysconf
+function may fail and set
+.Va errno
+for any of the errors specified for the library function
+.Xr sysctl 3 .
+In addition, the following error may be reported:
+.Bl -tag -width Er
+.It Bq Er EINVAL
+The value of the
+.Fa name
+argument is invalid.
+.El
+.Sh SEE ALSO
+.Xr getconf 1 ,
+.Xr pathconf 2 ,
+.Xr confstr 3 ,
+.Xr sysctl 3
+.Sh STANDARDS
+Except for the fact that values returned by
+.Fn sysconf
+may change over the lifetime of the calling process,
+this function conforms to
+.St -p1003.1-88 .
+.Sh HISTORY
+The
+.Fn sysconf
+function first appeared in
+.Bx 4.4 .
+.Sh BUGS
+The value for _SC_STREAM_MAX is a minimum maximum, and required to be
+the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
+small and misleading number.
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