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.Pp 64.Bl -tag -width 6n 65.Pp 66.It Li _SC_ARG_MAX 67The maximum bytes of argument to 68.Xr execve 2 . 69.It Li _SC_CHILD_MAX 70The maximum number of simultaneous processes per user id. 71.It Li _SC_CLK_TCK 72The frequency of the statistics clock in ticks per second. 73.It Li _SC_IOV_MAX 74The maximum number of elements in the I/O vector used by 75.Xr readv 2 , 76.Xr writev 2 , 77.Xr recvmsg 2 , 78and 79.Xr sendmsg 2 . 80.It Li _SC_NGROUPS_MAX 81The maximum number of supplemental groups. 82.It Li _SC_NPROCESSORS_CONF 83The number of processors configured. 84.It Li _SC_NPROCESSORS_ONLN 85The number of processors currently online. 86.It Li _SC_OPEN_MAX 87The maximum number of open files per user id. 88.It Li _SC_PAGESIZE 89The size of a system page in bytes. 90.It Li _SC_STREAM_MAX 91The minimum maximum number of streams that a process may have open 92at any one time. 93.It Li _SC_TZNAME_MAX 94The minimum maximum number of types supported for the name of a 95timezone. 96.It Li _SC_JOB_CONTROL 97Return 1 if job control is available on this system, otherwise \-1. 98.It Li _SC_SAVED_IDS 99Returns 1 if saved set-group and saved set-user ID is available, 100otherwise \-1. 101.It Li _SC_VERSION 102The version of 103.St -p1003.1 104with which the system 105attempts to comply. 106.It Li _SC_BC_BASE_MAX 107The maximum ibase/obase values in the 108.Xr bc 1 109utility. 110.It Li _SC_BC_DIM_MAX 111The maximum array size in the 112.Xr bc 1 113utility. 114.It Li _SC_BC_SCALE_MAX 115The maximum scale value in the 116.Xr bc 1 117utility. 118.It Li _SC_BC_STRING_MAX 119The maximum string length in the 120.Xr bc 1 121utility. 122.It Li _SC_COLL_WEIGHTS_MAX 123The maximum number of weights that can be assigned to any entry of 124the LC_COLLATE order keyword in the locale definition file. 125.It Li _SC_EXPR_NEST_MAX 126The maximum number of expressions that can be nested within 127parenthesis by the 128.Xr expr 1 129utility. 130.It Li _SC_LINE_MAX 131The maximum length in bytes of a text-processing utility's input 132line. 133.It Li _SC_RE_DUP_MAX 134The maximum number of repeated occurrences of a regular expression 135permitted when using interval notation. 136.It Li _SC_2_VERSION 137The version of 138.St -p1003.2 139with which the system attempts to comply. 140.It Li _SC_2_C_BIND 141Return 1 if the system's C-language development facilities support the 142C-Language Bindings Option, otherwise \-1. 143.It Li _SC_2_C_DEV 144Return 1 if the system supports the C-Language Development Utilities Option, 145otherwise \-1. 146.It Li _SC_2_CHAR_TERM 147Return 1 if the system supports at least one terminal type capable of 148all operations described in 149.St -p1003.2 , 150otherwise \-1. 151.It Li _SC_2_FORT_DEV 152Return 1 if the system supports the FORTRAN Development Utilities Option, 153otherwise \-1. 154.It Li _SC_2_FORT_RUN 155Return 1 if the system supports the FORTRAN Runtime Utilities Option, 156otherwise \-1. 157.It Li _SC_2_LOCALEDEF 158Return 1 if the system supports the creation of locales, otherwise \-1. 159.It Li _SC_2_SW_DEV 160Return 1 if the system supports the Software Development Utilities Option, 161otherwise \-1. 162.It Li _SC_2_UPE 163Return 1 if the system supports the User Portability Utilities Option, 164otherwise \-1. 165.El 166.Pp 167These values also exist, but may not be standard: 168.Pp 169.Bl -tag -width 6n 170.Pp 171.It Li _SC_PHYS_PAGES 172The number of pages of physical memory. 173Note that it is possible that the product of this value and the value of 174.Li _SC_PAGESIZE 175will overflow a 176.Vt long 177in some configurations on a 32bit machine. 178.El 179.Sh RETURN VALUES 180If the call to 181.Fn sysconf 182is not successful, \-1 is returned and 183.Va errno 184is set appropriately. 185Otherwise, if the variable is associated with functionality that is not 186supported, \-1 is returned and 187.Va errno 188is not modified. 189Otherwise, the current variable value is returned. 190.Sh ERRORS 191The 192.Fn sysconf 193function may fail and set 194.Va errno 195for any of the errors specified for the library function 196.Xr sysctl 3 . 197In addition, the following error may be reported: 198.Bl -tag -width Er 199.It Bq Er EINVAL 200The value of the 201.Fa name 202argument is invalid. 203.El 204.Sh SEE ALSO 205.Xr getconf 1 , 206.Xr pathconf 2 , 207.Xr confstr 3 , 208.Xr sysctl 3 209.Sh STANDARDS 210Except for the fact that values returned by 211.Fn sysconf 212may change over the lifetime of the calling process, 213this function conforms to 214.St -p1003.1-88 . 215.Sh HISTORY 216The 217.Fn sysconf 218function first appeared in 219.Bx 4.4 . 220.Sh BUGS 221The value for _SC_STREAM_MAX is a minimum maximum, and required to be 222the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 223small and misleading number. 224