1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 29.\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.8.2.6 2001/12/14 18:33:51 ru Exp $ 30.\" $DragonFly: src/lib/libc/gen/sysconf.3,v 1.7 2008/05/02 02:05:03 swildner Exp $ 31.\" 32.Dd November 7, 2009 33.Dt SYSCONF 3 34.Os 35.Sh NAME 36.Nm sysconf 37.Nd get configurable system variables 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft long 43.Fn sysconf "int name" 44.Sh DESCRIPTION 45This interface is defined by 46.St -p1003.1-88 . 47A far more complete interface is available using 48.Xr sysctl 3 . 49.Pp 50The 51.Fn sysconf 52function provides a method for applications to determine the current 53value of a configurable system limit or option variable. 54The 55.Fa name 56argument specifies the system variable to be queried. 57Symbolic constants for each name value are found in the include file 58.In unistd.h . 59.Pp 60The available values are as follows: 61.Bl -tag -width 6n 62.It Li _SC_ARG_MAX 63The maximum bytes of argument to 64.Xr execve 2 . 65.It Li _SC_BC_BASE_MAX 66The maximum ibase/obase values in the 67.Xr bc 1 68utility. 69.It Li _SC_BC_DIM_MAX 70The maximum array size in the 71.Xr bc 1 72utility. 73.It Li _SC_BC_SCALE_MAX 74The maximum scale value in the 75.Xr bc 1 76utility. 77.It Li _SC_BC_STRING_MAX 78The maximum string length in the 79.Xr bc 1 80utility. 81.It Li _SC_CHILD_MAX 82The maximum number of simultaneous processes per user id. 83.It Li _SC_CLK_TCK 84The frequency of the statistics clock in ticks per second. 85.It Li _SC_COLL_WEIGHTS_MAX 86The maximum number of weights that can be assigned to any entry of 87the LC_COLLATE order keyword in the locale definition file. 88.It Li _SC_EXPR_NEST_MAX 89The maximum number of expressions that can be nested within 90parenthesis by the 91.Xr expr 1 92utility. 93.It Li _SC_IOV_MAX 94The maximum number of elements in the I/O vector used by 95.Xr readv 2 , 96.Xr writev 2 , 97.Xr recvmsg 2 , 98and 99.Xr sendmsg 2 . 100.It Li _SC_JOB_CONTROL 101Return 1 if job control is available on this system, otherwise \-1. 102.It Li _SC_LINE_MAX 103The maximum length in bytes of a text-processing utility's input 104line. 105.It Li _SC_MESSAGE_PASSING 106Whether Message Passing option is supported. 107.It Li _SC_MQ_OPEN_MAX 108The maximum number of open message queue descriptors per process. 109.It Li _SC_MQ_PRIO_MAX 110The maximum number of message priorities supported by the implementation. 111.It Li _SC_NGROUPS_MAX 112The maximum number of supplemental groups. 113.It Li _SC_NPROCESSORS_CONF 114The number of processors configured. 115.It Li _SC_NPROCESSORS_ONLN 116The number of processors online. 117.It Li _SC_OPEN_MAX 118The maximum number of open files per user id. 119.It Li _SC_PAGESIZE 120The size of a system page in bytes. 121.It Li _SC_RE_DUP_MAX 122The maximum number of repeated occurrences of a regular expression 123permitted when using interval notation. 124.It Li _SC_SAVED_IDS 125Returns 1 if saved set-group and saved set-user ID is available, 126otherwise \-1. 127.It Li _SC_STREAM_MAX 128The minimum maximum number of streams that a process may have open 129at any one time. 130.It Li _SC_TZNAME_MAX 131The minimum maximum number of types supported for the name of a 132timezone. 133.It Li _SC_VERSION 134The version of 135.St -p1003.1 136with which the system 137attempts to comply. 138.It Li _SC_2_C_BIND 139Return 1 if the system's C-language development facilities support the 140C-Language Bindings Option, otherwise \-1. 141.It Li _SC_2_C_DEV 142Return 1 if the system supports the C-Language Development Utilities Option, 143otherwise \-1. 144.It Li _SC_2_CHAR_TERM 145Return 1 if the system supports at least one terminal type capable of 146all operations described in 147.St -p1003.2 , 148otherwise \-1. 149.It Li _SC_2_FORT_DEV 150Return 1 if the system supports the FORTRAN Development Utilities Option, 151otherwise \-1. 152.It Li _SC_2_FORT_RUN 153Return 1 if the system supports the FORTRAN Runtime Utilities Option, 154otherwise \-1. 155.It Li _SC_2_LOCALEDEF 156Return 1 if the system supports the creation of locales, otherwise \-1. 157.It Li _SC_2_SW_DEV 158Return 1 if the system supports the Software Development Utilities Option, 159otherwise \-1. 160.It Li _SC_2_UPE 161Return 1 if the system supports the User Portability Utilities Option, 162otherwise \-1. 163.It Li _SC_2_VERSION 164The version of 165.St -p1003.2 166with which the system attempts to comply. 167.El 168.Sh RETURN VALUES 169If the call to 170.Fn sysconf 171is not successful, \-1 is returned and 172.Va errno 173is set appropriately. 174Otherwise, if the variable is associated with functionality that is not 175supported, \-1 is returned and 176.Va errno 177is not modified. 178Otherwise, the current variable value is returned. 179.Sh ERRORS 180The 181.Fn sysconf 182function may fail and set 183.Va errno 184for any of the errors specified for the library function 185.Xr sysctl 3 . 186In addition, the following error may be reported: 187.Bl -tag -width Er 188.It Bq Er EINVAL 189The value of the 190.Fa name 191argument is invalid. 192.El 193.Sh SEE ALSO 194.Xr sysctl 3 195.Sh STANDARDS 196Except for the fact that values returned by 197.Fn sysconf 198may change over the lifetime of the calling process, 199this function conforms to 200.St -p1003.1-88 . 201.Pp 202_SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are nonstandard, but implemented 203in many systems. 204.Sh HISTORY 205The 206.Fn sysconf 207function first appeared in 208.Bx 4.4 . 209.Sh BUGS 210The value for _SC_STREAM_MAX is a minimum maximum, and required to be 211the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 212small and misleading number. 213