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 June 18, 2001 36.Dt SYSCONF 3 37.Os BSD 4 38.Sh NAME 39.Nm sysconf 40.Nd get configurable system variables 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.Fd #include <unistd.h> 45.Ft long 46.Fn sysconf "int name" 47.Sh DESCRIPTION 48.Pp 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 . 63Shell programmers who need access to these parameters should use the 64.Xr getconf 1 65utility. 66.Pp 67The available values are as follows: 68.Pp 69.Bl -tag -width 6n 70.Pp 71.It Li _SC_ARG_MAX 72The maximum bytes of argument to 73.Xr execve 2 . 74.It Li _SC_CHILD_MAX 75The maximum number of simultaneous processes per user id. 76.It Li _SC_CLK_TCK 77The frequency of the statistics clock in ticks per second. 78.It Li _SC_IOV_MAX 79The maximum number of elements in the I/O vector used by 80.Xr readv 2 , 81.Xr writev 2 , 82.Xr recvmsg 2 , 83and 84.Xr sendmsg 2 . 85.It Li _SC_NGROUPS_MAX 86The maximum number of supplemental groups. 87.It Li _SC_OPEN_MAX 88The maximum number of open files per user id. 89.It Li _SC_STREAM_MAX 90The minimum maximum number of streams that a process may have open 91at any one time. 92.It Li _SC_TZNAME_MAX 93The minimum maximum number of types supported for the name of a 94timezone. 95.It Li _SC_JOB_CONTROL 96Return 1 if job control is available on this system, otherwise \-1. 97.It Li _SC_SAVED_IDS 98Returns 1 if saved set-group and saved set-user ID is available, 99otherwise \-1. 100.It Li _SC_VERSION 101The version of 102.St -p1003.1 103with which the system 104attempts to comply. 105.It Li _SC_BC_BASE_MAX 106The maximum ibase/obase values in the 107.Xr bc 1 108utility. 109.It Li _SC_BC_DIM_MAX 110The maximum array size in the 111.Xr bc 1 112utility. 113.It Li _SC_BC_SCALE_MAX 114The maximum scale value in the 115.Xr bc 1 116utility. 117.It Li _SC_BC_STRING_MAX 118The maximum string length in the 119.Xr bc 1 120utility. 121.It Li _SC_COLL_WEIGHTS_MAX 122The maximum number of weights that can be assigned to any entry of 123the LC_COLLATE order keyword in the locale definition file. 124.It Li _SC_EXPR_NEST_MAX 125The maximum number of expressions that can be nested within 126parenthesis by the 127.Xr expr 1 128utility. 129.It Li _SC_LINE_MAX 130The maximum length in bytes of a text-processing utility's input 131line. 132.It Li _SC_RE_DUP_MAX 133The maximum number of repeated occurrences of a regular expression 134permitted when using interval notation. 135.It Li _SC_2_VERSION 136The version of 137.St -p1003.2 138with which the system attempts to comply. 139.It Li _SC_2_C_BIND 140Return 1 if the system's C-language development facilities support the 141C-Language Bindings Option, otherwise \-1. 142.It Li _SC_2_C_DEV 143Return 1 if the system supports the C-Language Development Utilities Option, 144otherwise \-1. 145.It Li _SC_2_CHAR_TERM 146Return 1 if the system supports at least one terminal type capable of 147all operations described in 148.St -p1003.2 , 149otherwise \-1. 150.It Li _SC_2_FORT_DEV 151Return 1 if the system supports the FORTRAN Development Utilities Option, 152otherwise \-1. 153.It Li _SC_2_FORT_RUN 154Return 1 if the system supports the FORTRAN Runtime Utilities Option, 155otherwise \-1. 156.It Li _SC_2_LOCALEDEF 157Return 1 if the system supports the creation of locales, otherwise \-1. 158.It Li _SC_2_SW_DEV 159Return 1 if the system supports the Software Development Utilities Option, 160otherwise \-1. 161.It Li _SC_2_UPE 162Return 1 if the system supports the User Portability Utilities Option, 163otherwise \-1. 164.El 165.Sh RETURN VALUES 166If the call to 167.Fn sysconf 168is not successful, \-1 is returned and 169.Va errno 170is set appropriately. 171Otherwise, if the variable is associated with functionality that is not 172supported, \-1 is returned and 173.Va errno 174is not modified. 175Otherwise, the current variable value is returned. 176.Sh ERRORS 177The 178.Fn sysconf 179function may fail and set 180.Va errno 181for any of the errors specified for the library function 182.Xr sysctl 3 . 183In addition, the following error may be reported: 184.Bl -tag -width Er 185.It Bq Er EINVAL 186The value of the 187.Fa name 188argument is invalid. 189.El 190.Sh SEE ALSO 191.Xr getconf 1 , 192.Xr pathconf 2 , 193.Xr confstr 3 , 194.Xr sysctl 3 195.Sh BUGS 196The value for _SC_STREAM_MAX is a minimum maximum, and required to be 197the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 198small and misleading number. 199.Sh STANDARDS 200Except for the fact that values returned by 201.Fn sysconf 202may change over the lifetime of the calling process, 203this function conforms to 204.St -p1003.1-88 . 205.Sh HISTORY 206The 207.Fn sysconf 208function first appeared in 209.Bx 4.4 . 210