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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 33.\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.8.2.6 2001/12/14 18:33:51 ru Exp $ 34.\" $DragonFly: src/lib/libc/gen/sysconf.3,v 1.4 2006/02/17 19:35:06 swildner Exp $ 35.\" 36.Dd April 19, 1994 37.Dt SYSCONF 3 38.Os 39.Sh NAME 40.Nm sysconf 41.Nd get configurable system variables 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft long 47.Fn sysconf "int name" 48.Sh DESCRIPTION 49This interface is defined by 50.St -p1003.1-88 . 51A far more complete interface is available using 52.Xr sysctl 3 . 53.Pp 54The 55.Fn sysconf 56function provides a method for applications to determine the current 57value of a configurable system limit or option variable. 58The 59.Fa name 60argument specifies the system variable to be queried. 61Symbolic constants for each name value are found in the include file 62.Aq Pa unistd.h . 63.Pp 64The available values are as follows: 65.Pp 66.Bl -tag -width 6n 67.Pp 68.It Li _SC_ARG_MAX 69The maximum bytes of argument to 70.Xr execve 2 . 71.It Li _SC_CHILD_MAX 72The maximum number of simultaneous processes per user id. 73.It Li _SC_CLK_TCK 74The frequency of the statistics clock in ticks per second. 75.It Li _SC_IOV_MAX 76The maximum number of elements in the I/O vector used by 77.Xr readv 2 , 78.Xr writev 2 , 79.Xr recvmsg 2 , 80and 81.Xr sendmsg 2 . 82.It Li _SC_NGROUPS_MAX 83The maximum number of supplemental groups. 84.It Li _SC_OPEN_MAX 85The maximum number of open files per user id. 86.It Li _SC_STREAM_MAX 87The minimum maximum number of streams that a process may have open 88at any one time. 89.It Li _SC_TZNAME_MAX 90The minimum maximum number of types supported for the name of a 91timezone. 92.It Li _SC_JOB_CONTROL 93Return 1 if job control is available on this system, otherwise \-1. 94.It Li _SC_SAVED_IDS 95Returns 1 if saved set-group and saved set-user ID is available, 96otherwise \-1. 97.It Li _SC_VERSION 98The version of 99.St -p1003.1 100with which the system 101attempts to comply. 102.It Li _SC_BC_BASE_MAX 103The maximum ibase/obase values in the 104.Xr bc 1 105utility. 106.It Li _SC_BC_DIM_MAX 107The maximum array size in the 108.Xr bc 1 109utility. 110.It Li _SC_BC_SCALE_MAX 111The maximum scale value in the 112.Xr bc 1 113utility. 114.It Li _SC_BC_STRING_MAX 115The maximum string length in the 116.Xr bc 1 117utility. 118.It Li _SC_COLL_WEIGHTS_MAX 119The maximum number of weights that can be assigned to any entry of 120the LC_COLLATE order keyword in the locale definition file. 121.It Li _SC_EXPR_NEST_MAX 122The maximum number of expressions that can be nested within 123parenthesis by the 124.Xr expr 1 125utility. 126.It Li _SC_LINE_MAX 127The maximum length in bytes of a text-processing utility's input 128line. 129.It Li _SC_RE_DUP_MAX 130The maximum number of repeated occurrences of a regular expression 131permitted when using interval notation. 132.It Li _SC_2_VERSION 133The version of 134.St -p1003.2 135with which the system attempts to comply. 136.It Li _SC_2_C_BIND 137Return 1 if the system's C-language development facilities support the 138C-Language Bindings Option, otherwise \-1. 139.It Li _SC_2_C_DEV 140Return 1 if the system supports the C-Language Development Utilities Option, 141otherwise \-1. 142.It Li _SC_2_CHAR_TERM 143Return 1 if the system supports at least one terminal type capable of 144all operations described in 145.St -p1003.2 , 146otherwise \-1. 147.It Li _SC_2_FORT_DEV 148Return 1 if the system supports the FORTRAN Development Utilities Option, 149otherwise \-1. 150.It Li _SC_2_FORT_RUN 151Return 1 if the system supports the FORTRAN Runtime Utilities Option, 152otherwise \-1. 153.It Li _SC_2_LOCALEDEF 154Return 1 if the system supports the creation of locales, otherwise \-1. 155.It Li _SC_2_SW_DEV 156Return 1 if the system supports the Software Development Utilities Option, 157otherwise \-1. 158.It Li _SC_2_UPE 159Return 1 if the system supports the User Portability Utilities Option, 160otherwise \-1. 161.El 162.Sh RETURN VALUES 163If the call to 164.Fn sysconf 165is not successful, \-1 is returned and 166.Va errno 167is set appropriately. 168Otherwise, if the variable is associated with functionality that is not 169supported, \-1 is returned and 170.Va errno 171is not modified. 172Otherwise, the current variable value is returned. 173.Sh ERRORS 174The 175.Fn sysconf 176function may fail and set 177.Va errno 178for any of the errors specified for the library function 179.Xr sysctl 3 . 180In addition, the following error may be reported: 181.Bl -tag -width Er 182.It Bq Er EINVAL 183The value of the 184.Fa name 185argument is invalid. 186.El 187.Sh SEE ALSO 188.Xr sysctl 3 189.Sh STANDARDS 190Except for the fact that values returned by 191.Fn sysconf 192may change over the lifetime of the calling process, 193this function conforms to 194.St -p1003.1-88 . 195.Sh HISTORY 196The 197.Fn sysconf 198function first appeared in 199.Bx 4.4 . 200.Sh BUGS 201The value for _SC_STREAM_MAX is a minimum maximum, and required to be 202the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 203small and misleading number. 204