1.\" $NetBSD: sysconf.3,v 1.10 1999/03/09 19:45:09 erh Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 35.\" 36.Dd April 19, 1994 37.Dt SYSCONF 3 38.Os BSD 4 39.Sh NAME 40.Nm sysconf 41.Nd get configurable system variables 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include <unistd.h> 46.Ft long 47.Fn sysconf "int name" 48.Sh DESCRIPTION 49.Pp 50This interface is defined by 51.St -p1003.1-88 . 52A far more complete interface is available using 53.Xr sysctl 3 . 54.Pp 55The 56.Fn sysconf 57function provides a method for applications to determine the current 58value of a configurable system limit or option variable. 59The 60.Fa name 61argument specifies the system variable to be queried. 62Symbolic constants for each name value are found in the include file 63.Li <unistd.h> . 64.Pp 65The available values are as follows: 66.Pp 67.Bl -tag -width "123456" 68.Pp 69.It Li _SC_ARG_MAX 70The maximum bytes of argument to 71.Xr execve 2 . 72.It Li _SC_CHILD_MAX 73The maximum number of simultaneous processes per user id. 74.It Li _SC_CLK_TCK 75The number of clock ticks per second. 76.It Li _SC_FSYNC 77Return 1 if the File Synchronization Option is available on this system, 78otherwise \-1. 79.It Li _SC_IOV_MAX 80The maximum number of 81.Va iovec 82structures that a process has available for use with 83.Xr preadv 2 , 84.Xr pwritev 2 , 85.Xr readv 2 , 86.Xr recvmsg 2 , 87.Xr sendmsg 2 88or 89.Xr writev 2 . 90.It Li _SC_JOB_CONTROL 91Return 1 if job control is available on this system, otherwise \-1. 92.It Li _SC_NGROUPS_MAX 93The maximum number of supplemental groups. 94.It Li _SC_OPEN_MAX 95The maximum number of open files per user id. 96.It Li _SC_PAGESIZE 97The size of a system page in bytes. 98.It Li _SC_STREAM_MAX 99The minimum maximum number of streams that a process may have open 100at any one time. 101.It Li _SC_SYNCHRONIZED_IO 102Return 1 if the Synchronized I/O Option is available on this system, 103otherwise \-1. 104.It Li _SC_TZNAME_MAX 105The minimum maximum number of types supported for the name of a 106timezone. 107.It Li _SC_SAVED_IDS 108Returns 1 if saved set-group and saved set-user ID is available, 109otherwise \-1. 110.It Li _SC_VERSION 111The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 112attempts to comply. 113.It Li _SC_BC_BASE_MAX 114The maximum ibase/obase values in the 115.Xr bc 1 116utility. 117.It Li _SC_BC_DIM_MAX 118The maximum array size in the 119.Xr bc 1 120utility. 121.It Li _SC_BC_SCALE_MAX 122The maximum scale value in the 123.Xr bc 1 124utility. 125.It Li _SC_BC_STRING_MAX 126The maximum string length in the 127.Xr bc 1 128utility. 129.It Li _SC_COLL_WEIGHTS_MAX 130The maximum number of weights that can be assigned to any entry of 131the LC_COLLATE order keyword in the locale definition file. 132.It Li _SC_EXPR_NEST_MAX 133The maximum number of expressions that can be nested within 134parenthesis by the 135.Xr expr 1 136utility. 137.It Li _SC_LINE_MAX 138The maximum length in bytes of a text-processing utility's input 139line. 140.It Li _SC_RE_DUP_MAX 141The maximum number of repeated occurrences of a regular expression 142permitted when using interval notation. 143.It Li _SC_2_VERSION 144The version of POSIX 1003.2 with which the system attempts to comply. 145.It Li _SC_2_C_BIND 146Return 1 if the system's C-language development facilities support the 147C-Language Bindings Option, otherwise \-1. 148.It Li _SC_2_C_DEV 149Return 1 if the system supports the C-Language Development Utilities Option, 150otherwise \-1. 151.It Li _SC_2_CHAR_TERM 152Return 1 if the system supports at least one terminal type capable of 153all operations described in POSIX 1003.2, otherwise \-1. 154.It Li _SC_2_FORT_DEV 155Return 1 if the system supports the FORTRAN Development Utilities Option, 156otherwise \-1. 157.It Li _SC_2_FORT_RUN 158Return 1 if the system supports the FORTRAN Runtime Utilities Option, 159otherwise \-1. 160.It Li _SC_2_LOCALEDEF 161Return 1 if the system supports the creation of locales, otherwise \-1. 162.It Li _SC_2_SW_DEV 163Return 1 if the system supports the Software Development Utilities Option, 164otherwise \-1. 165.It Li _SC_2_UPE 166Return 1 if the system supports the User Portability Utilities Option, 167otherwise \-1. 168.It Li _SC_XOPEN_SHM 169Return 1 of the system supports System V style shared memory, 170otherwise \-1. 171.El 172.Sh RETURN VALUES 173If the call to 174.Nm sysconf 175is not successful, \-1 is returned and 176.Va errno 177is set appropriately. 178Otherwise, if the variable is associated with functionality that is not 179supported, \-1 is returned and 180.Va errno 181is not modified. 182Otherwise, the current variable value is returned. 183.Sh ERRORS 184The 185.Fn sysconf 186function may fail and set 187.Va errno 188for any of the errors specified for the library functions 189.Xr sysctl 3 . 190In addition, the following error may be reported: 191.Bl -tag -width Er 192.It Bq Er EINVAL 193The value of the 194.Fa name 195argument is invalid. 196.El 197.Sh SEE ALSO 198.Xr sysctl 3 199.Sh BUGS 200The value for _SC_STREAM_MAX is a minimum maximum, and required to be 201the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 202small and misleading number. 203.Sh STANDARDS 204The 205.Fn sysconf 206function conforms to 207.St -p1003.1-90 . 208.Sh HISTORY 209The 210.Nm sysconf 211function first appeared in 212.Bx 4.4 . 213