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.\" $FreeBSD$ 34.\" 35.Dd December 14, 2006 36.Dt SYSCONF 3 37.Os 38.Sh NAME 39.Nm sysconf 40.Nd get configurable system variables 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft long 46.Fn sysconf "int name" 47.Sh DESCRIPTION 48This interface is defined by 49.St -p1003.1-88 . 50A far more complete interface is available using 51.Xr sysctl 3 . 52.Pp 53The 54.Fn sysconf 55function provides a method for applications to determine the current 56value of a configurable system limit or option variable. 57The 58.Fa name 59argument specifies the system variable to be queried. 60Symbolic constants for each name value are found in the include file 61.In unistd.h . 62Shell programmers who need access to these parameters should use the 63.Xr getconf 1 64utility. 65.Pp 66The available values are as follows: 67.Pp 68.Bl -tag -width 6n 69.Pp 70.It Li _SC_ARG_MAX 71The maximum bytes of argument to 72.Xr execve 2 . 73.It Li _SC_CHILD_MAX 74The maximum number of simultaneous processes per user id. 75.It Li _SC_CLK_TCK 76The frequency of the statistics clock in ticks per second. 77.It Li _SC_IOV_MAX 78The maximum number of elements in the I/O vector used by 79.Xr readv 2 , 80.Xr writev 2 , 81.Xr recvmsg 2 , 82and 83.Xr sendmsg 2 . 84.It Li _SC_NGROUPS_MAX 85The maximum number of supplemental groups. 86.It Li _SC_NPROCESSORS_CONF 87The number of processors configured. 88.It Li _SC_NPROCESSORS_ONLN 89The number of processors currently online. 90.It Li _SC_OPEN_MAX 91The maximum number of open files per user id. 92.It Li _SC_PAGESIZE 93The size of a system page in bytes. 94.It Li _SC_STREAM_MAX 95The minimum maximum number of streams that a process may have open 96at any one time. 97.It Li _SC_TZNAME_MAX 98The minimum maximum number of types supported for the name of a 99timezone. 100.It Li _SC_JOB_CONTROL 101Return 1 if job control is available on this system, otherwise \-1. 102.It Li _SC_SAVED_IDS 103Returns 1 if saved set-group and saved set-user ID is available, 104otherwise \-1. 105.It Li _SC_VERSION 106The version of 107.St -p1003.1 108with which the system 109attempts to comply. 110.It Li _SC_BC_BASE_MAX 111The maximum ibase/obase values in the 112.Xr bc 1 113utility. 114.It Li _SC_BC_DIM_MAX 115The maximum array size in the 116.Xr bc 1 117utility. 118.It Li _SC_BC_SCALE_MAX 119The maximum scale value in the 120.Xr bc 1 121utility. 122.It Li _SC_BC_STRING_MAX 123The maximum string length in the 124.Xr bc 1 125utility. 126.It Li _SC_COLL_WEIGHTS_MAX 127The maximum number of weights that can be assigned to any entry of 128the LC_COLLATE order keyword in the locale definition file. 129.It Li _SC_EXPR_NEST_MAX 130The maximum number of expressions that can be nested within 131parenthesis by the 132.Xr expr 1 133utility. 134.It Li _SC_LINE_MAX 135The maximum length in bytes of a text-processing utility's input 136line. 137.It Li _SC_RE_DUP_MAX 138The maximum number of repeated occurrences of a regular expression 139permitted when using interval notation. 140.It Li _SC_2_VERSION 141The version of 142.St -p1003.2 143with which the system attempts to comply. 144.It Li _SC_2_C_BIND 145Return 1 if the system's C-language development facilities support the 146C-Language Bindings Option, otherwise \-1. 147.It Li _SC_2_C_DEV 148Return 1 if the system supports the C-Language Development Utilities Option, 149otherwise \-1. 150.It Li _SC_2_CHAR_TERM 151Return 1 if the system supports at least one terminal type capable of 152all operations described in 153.St -p1003.2 , 154otherwise \-1. 155.It Li _SC_2_FORT_DEV 156Return 1 if the system supports the FORTRAN Development Utilities Option, 157otherwise \-1. 158.It Li _SC_2_FORT_RUN 159Return 1 if the system supports the FORTRAN Runtime Utilities Option, 160otherwise \-1. 161.It Li _SC_2_LOCALEDEF 162Return 1 if the system supports the creation of locales, otherwise \-1. 163.It Li _SC_2_SW_DEV 164Return 1 if the system supports the Software Development Utilities Option, 165otherwise \-1. 166.It Li _SC_2_UPE 167Return 1 if the system supports the User Portability Utilities Option, 168otherwise \-1. 169.El 170.Pp 171These values also exist, but may not be standard: 172.Pp 173.Bl -tag -width 6n 174.Pp 175.It Li _SC_PHYS_PAGES 176The number of pages of physical memory. 177Note that it is possible that the product of this value and the value of 178.Li _SC_PAGESIZE 179will overflow a 180.Vt long 181in some configurations on a 32bit machine. 182.El 183.Sh RETURN VALUES 184If the call to 185.Fn sysconf 186is not successful, \-1 is returned and 187.Va errno 188is set appropriately. 189Otherwise, if the variable is associated with functionality that is not 190supported, \-1 is returned and 191.Va errno 192is not modified. 193Otherwise, the current variable value is returned. 194.Sh ERRORS 195The 196.Fn sysconf 197function may fail and set 198.Va errno 199for any of the errors specified for the library function 200.Xr sysctl 3 . 201In addition, the following error may be reported: 202.Bl -tag -width Er 203.It Bq Er EINVAL 204The value of the 205.Fa name 206argument is invalid. 207.El 208.Sh SEE ALSO 209.Xr getconf 1 , 210.Xr pathconf 2 , 211.Xr confstr 3 , 212.Xr sysctl 3 213.Sh STANDARDS 214Except for the fact that values returned by 215.Fn sysconf 216may change over the lifetime of the calling process, 217this function conforms to 218.St -p1003.1-88 . 219.Sh HISTORY 220The 221.Fn sysconf 222function first appeared in 223.Bx 4.4 . 224.Sh BUGS 225The value for _SC_STREAM_MAX is a minimum maximum, and required to be 226the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 227small and misleading number. 228