1.\" $NetBSD: sysconf.3,v 1.25 2003/05/01 13:58:03 wiz 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 February 2, 2003 37.Dt SYSCONF 3 38.Os 39.Sh NAME 40.Nm sysconf 41.Nd get configurable system variables 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft long 47.Fn sysconf "int name" 48.Sh DESCRIPTION 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 . 63.Pp 64The available values are as follows: 65.Pp 66.Bl -tag -width "123456" 67.Pp 68.It Li _SC_ARG_MAX 69The maximum bytes of argument to 70.Xr execve 2 . 71.It Li _SC_ATEXIT_MAX 72The maxmimum number of functions that may be registered with 73.Xr atexit 3 . 74.It Li _SC_BARRIERS 75The version of 76.St -p1003.1 77and its 78Barriers 79option to which the system attempts to conform, 80otherwise \-1. 81.It Li _SC_CHILD_MAX 82The maximum number of simultaneous processes per user id. 83.It Li _SC_CLK_TCK 84The number of clock ticks per second. 85.It Li _SC_FSYNC 86Return 1 if the File Synchronization Option is available on this system, 87otherwise \-1. 88.It Li _SC_IOV_MAX 89The maximum number of 90.Va iovec 91structures that a process has available for use with 92.Xr preadv 2 , 93.Xr pwritev 2 , 94.Xr readv 2 , 95.Xr recvmsg 2 , 96.Xr sendmsg 2 97or 98.Xr writev 2 . 99.It Li _SC_JOB_CONTROL 100Return 1 if job control is available on this system, otherwise \-1. 101.It Li _SC_LOGIN_NAME_MAX 102Returns the size of the storage required for a login name, in bytes, 103including the terminating NUL. 104.It Li _SC_MAPPED_FILES 105Return 1 if the Memory Mapped Files Option is available on this system, 106otherwise \-1. 107.It Li _SC_MEMLOCK 108Return 1 if the Process Memory Locking Option is available on this system, 109otherwise \-1. 110.It Li _SC_MEMLOCK_RANGE 111Return 1 if the Range Memory Locking Option is available on this system, 112otherwise \-1. 113.It Li _SC_MEMORY_PROTECTION 114Return 1 if the Memory Protection Option is available on this system, 115otherwise \-1. 116.It Li _SC_MONOTONIC_CLOCK 117Return the 118.Tn POSIX 119version the implementation of the Monotonic Clock Option 120on this system conforms to, 121or \-1 if unavailable. 122.It Li _SC_NGROUPS_MAX 123The maximum number of supplemental groups. 124.It Li _SC_OPEN_MAX 125The maximum number of open files per process. 126.It Li _SC_PAGESIZE 127The size of a system page in bytes. 128.It Li _SC_READER_WRITER_LOCKS 129The version of 130.St -p1003.1 131and its 132Read-Write Locks 133option to which the system attempts to conform, 134otherwise \-1. 135.It Li _SC_SEMAPHORES 136The version of 137.St -p1003.1 138and its 139Semaphores 140option to which the system attempts to conform, 141otherwise \-1. 142.It Li _SC_SPIN_LOCKS 143The version of 144.St -p1003.1 145and its 146Spin Locks 147option to which the system attempts to conform, 148otherwise \-1. 149.It Li _SC_STREAM_MAX 150The minimum maximum number of streams that a process may have open 151at any one time. 152.It Li _SC_SYNCHRONIZED_IO 153Return 1 if the Synchronized I/O Option is available on this system, 154otherwise \-1. 155.It Li _SC_THREADS 156The version of 157.St -p1003.1 158and its 159Threads 160option to which the system attempts to conform, 161otherwise \-1. 162.It Li _SC_TIMERS 163The version of 164.St -p1003.1 165and its 166Timers 167option to which the system attempts to conform, 168otherwise \-1. 169.It Li _SC_TZNAME_MAX 170The minimum maximum number of types supported for the name of a 171timezone. 172.It Li _SC_SAVED_IDS 173Returns 1 if saved set-group and saved set-user ID is available, 174otherwise \-1. 175.It Li _SC_VERSION 176The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 177attempts to comply. 178.It Li _SC_XOPEN_SHM 179Return 1 of the system supports System V style shared memory, 180otherwise \-1. 181.It Li _SC_BC_BASE_MAX 182The maximum ibase/obase values in the 183.Xr bc 1 184utility. 185.It Li _SC_BC_DIM_MAX 186The maximum array size in the 187.Xr bc 1 188utility. 189.It Li _SC_BC_SCALE_MAX 190The maximum scale value in the 191.Xr bc 1 192utility. 193.It Li _SC_BC_STRING_MAX 194The maximum string length in the 195.Xr bc 1 196utility. 197.It Li _SC_COLL_WEIGHTS_MAX 198The maximum number of weights that can be assigned to any entry of 199the LC_COLLATE order keyword in the locale definition file. 200.It Li _SC_EXPR_NEST_MAX 201The maximum number of expressions that can be nested within 202parenthesis by the 203.Xr expr 1 204utility. 205.It Li _SC_LINE_MAX 206The maximum length in bytes of a text-processing utility's input 207line. 208.It Li _SC_RE_DUP_MAX 209The maximum number of repeated occurrences of a regular expression 210permitted when using interval notation. 211.It Li _SC_2_VERSION 212The version of POSIX 1003.2 with which the system attempts to comply. 213.It Li _SC_2_C_BIND 214Return 1 if the system's C-language development facilities support the 215C-Language Bindings Option, otherwise \-1. 216.It Li _SC_2_C_DEV 217Return 1 if the system supports the C-Language Development Utilities Option, 218otherwise \-1. 219.It Li _SC_2_CHAR_TERM 220Return 1 if the system supports at least one terminal type capable of 221all operations described in POSIX 1003.2, otherwise \-1. 222.It Li _SC_2_FORT_DEV 223Return 1 if the system supports the FORTRAN Development Utilities Option, 224otherwise \-1. 225.It Li _SC_2_FORT_RUN 226Return 1 if the system supports the FORTRAN Runtime Utilities Option, 227otherwise \-1. 228.It Li _SC_2_LOCALEDEF 229Return 1 if the system supports the creation of locales, otherwise \-1. 230.It Li _SC_2_SW_DEV 231Return 1 if the system supports the Software Development Utilities Option, 232otherwise \-1. 233.It Li _SC_2_UPE 234Return 1 if the system supports the User Portability Utilities Option, 235otherwise \-1. 236.El 237.Sh RETURN VALUES 238If the call to 239.Nm sysconf 240is not successful, \-1 is returned and 241.Va errno 242is set appropriately. 243Otherwise, if the variable is associated with functionality that is not 244supported, \-1 is returned and 245.Va errno 246is not modified. 247Otherwise, the current variable value is returned. 248.Sh ERRORS 249The 250.Fn sysconf 251function may fail and set 252.Va errno 253for any of the errors specified for the library functions 254.Xr sysctl 3 . 255In addition, the following error may be reported: 256.Bl -tag -width Er 257.It Bq Er EINVAL 258The value of the 259.Fa name 260argument is invalid. 261.El 262.Sh SEE ALSO 263.Xr sysctl 3 264.Sh STANDARDS 265The 266.Fn sysconf 267function conforms to 268.St -p1003.1-90 . 269.Sh HISTORY 270The 271.Nm sysconf 272function first appeared in 273.Bx 4.4 . 274.Sh BUGS 275The value for _SC_STREAM_MAX is a minimum maximum, and required to be 276the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 277small and misleading number. 278