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.\" 4. 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.\" $FreeBSD$ 30.\" 31.Dd December 14, 2006 32.Dt SYSCONF 3 33.Os 34.Sh NAME 35.Nm sysconf 36.Nd get configurable system variables 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft long 42.Fn sysconf "int name" 43.Sh DESCRIPTION 44This interface is defined by 45.St -p1003.1-88 . 46A far more complete interface is available using 47.Xr sysctl 3 . 48.Pp 49The 50.Fn sysconf 51function provides a method for applications to determine the current 52value of a configurable system limit or option variable. 53The 54.Fa name 55argument specifies the system variable to be queried. 56Symbolic constants for each name value are found in the include file 57.In unistd.h . 58Shell programmers who need access to these parameters should use the 59.Xr getconf 1 60utility. 61.Pp 62The available values are as follows: 63.Bl -tag -width 6n 64.It Li _SC_ARG_MAX 65The maximum bytes of argument to 66.Xr execve 2 . 67.It Li _SC_CHILD_MAX 68The maximum number of simultaneous processes per user id. 69.It Li _SC_CLK_TCK 70The frequency of the statistics clock in ticks per second. 71.It Li _SC_IOV_MAX 72The maximum number of elements in the I/O vector used by 73.Xr readv 2 , 74.Xr writev 2 , 75.Xr recvmsg 2 , 76and 77.Xr sendmsg 2 . 78.It Li _SC_NGROUPS_MAX 79The maximum number of supplemental groups. 80.It Li _SC_NPROCESSORS_CONF 81The number of processors configured. 82.It Li _SC_NPROCESSORS_ONLN 83The number of processors currently online. 84.It Li _SC_OPEN_MAX 85The maximum number of open files per user id. 86.It Li _SC_PAGESIZE 87The size of a system page in bytes. 88.It Li _SC_STREAM_MAX 89The minimum maximum number of streams that a process may have open 90at any one time. 91.It Li _SC_TZNAME_MAX 92The minimum maximum number of types supported for the name of a 93timezone. 94.It Li _SC_JOB_CONTROL 95Return 1 if job control is available on this system, otherwise \-1. 96.It Li _SC_SAVED_IDS 97Returns 1 if saved set-group and saved set-user ID is available, 98otherwise \-1. 99.It Li _SC_VERSION 100The version of 101.St -p1003.1 102with which the system 103attempts to comply. 104.It Li _SC_BC_BASE_MAX 105The maximum ibase/obase values in the 106.Xr bc 1 107utility. 108.It Li _SC_BC_DIM_MAX 109The maximum array size in the 110.Xr bc 1 111utility. 112.It Li _SC_BC_SCALE_MAX 113The maximum scale value in the 114.Xr bc 1 115utility. 116.It Li _SC_BC_STRING_MAX 117The maximum string length in the 118.Xr bc 1 119utility. 120.It Li _SC_COLL_WEIGHTS_MAX 121The maximum number of weights that can be assigned to any entry of 122the LC_COLLATE order keyword in the locale definition file. 123.It Li _SC_EXPR_NEST_MAX 124The maximum number of expressions that can be nested within 125parenthesis by the 126.Xr expr 1 127utility. 128.It Li _SC_LINE_MAX 129The maximum length in bytes of a text-processing utility's input 130line. 131.It Li _SC_RE_DUP_MAX 132The maximum number of repeated occurrences of a regular expression 133permitted when using interval notation. 134.It Li _SC_2_VERSION 135The version of 136.St -p1003.2 137with which the system attempts 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.El 164.Pp 165These values also exist, but may not be standard: 166.Bl -tag -width 6n 167.It Li _SC_PHYS_PAGES 168The number of pages of physical memory. 169Note that it is possible that the product of this value and the value of 170.Li _SC_PAGESIZE 171will overflow a 172.Vt long 173in some configurations on a 32bit machine. 174.El 175.Sh RETURN VALUES 176If the call to 177.Fn sysconf 178is not successful, \-1 is returned and 179.Va errno 180is set appropriately. 181Otherwise, if the variable is associated with functionality that is not 182supported, \-1 is returned and 183.Va errno 184is not modified. 185Otherwise, the current variable value is returned. 186.Sh ERRORS 187The 188.Fn sysconf 189function may fail and set 190.Va errno 191for any of the errors specified for the library function 192.Xr sysctl 3 . 193In addition, the following error may be reported: 194.Bl -tag -width Er 195.It Bq Er EINVAL 196The value of the 197.Fa name 198argument is invalid. 199.El 200.Sh SEE ALSO 201.Xr getconf 1 , 202.Xr pathconf 2 , 203.Xr confstr 3 , 204.Xr sysctl 3 205.Sh STANDARDS 206Except for the fact that values returned by 207.Fn sysconf 208may change over the lifetime of the calling process, 209this function conforms to 210.St -p1003.1-88 . 211.Sh HISTORY 212The 213.Fn sysconf 214function first appeared in 215.Bx 4.4 . 216.Sh BUGS 217The value for _SC_STREAM_MAX is a minimum maximum, and required to be 218the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 219small and misleading number. 220