1.\" $NetBSD: sysconf.3,v 1.37 2010/03/22 19:30:54 joerg 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 31.\" 32.Dd August 6, 2008 33.Dt SYSCONF 3 34.Os 35.Sh NAME 36.Nm sysconf 37.Nd get configurable system variables 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft long 43.Fn sysconf "int name" 44.Sh DESCRIPTION 45This interface is defined by 46.St -p1003.1-88 . 47A far more complete interface is available using 48.Xr sysctl 3 . 49.Pp 50The 51.Fn sysconf 52function provides a method for applications to determine the current 53value of a configurable system limit or option variable. 54The 55.Fa name 56argument specifies the system variable to be queried. 57Symbolic constants for each name value are found in the include file 58.In unistd.h . 59.Pp 60The available values are as follows: 61.Bl -tag -width "123456" 62.It Li _SC_ARG_MAX 63The maximum bytes of argument to 64.Xr execve 2 . 65.It Li _SC_ATEXIT_MAX 66The maxmimum number of functions that may be registered with 67.Xr atexit 3 . 68.It Li _SC_BARRIERS 69The version of 70.St -p1003.1 71and its 72Barriers 73option to which the system attempts to conform, 74otherwise \-1. 75.It Li _SC_CLOCK_SELECTION 76Return the 77.Tn POSIX 78version the implementation of the Clock Selection Option 79on this system conforms to, 80or \-1 if unavailable. 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_HOST_NAME_MAX 89The maximum size of a hostname, including NULL. 90.It Li _SC_IOV_MAX 91The maximum number of 92.Va iovec 93structures that a process has available for use with 94.Xr preadv 2 , 95.Xr pwritev 2 , 96.Xr readv 2 , 97.Xr recvmsg 2 , 98.Xr sendmsg 2 99or 100.Xr writev 2 . 101.It Li _SC_JOB_CONTROL 102Return 1 if job control is available on this system, otherwise \-1. 103.It Li _SC_LOGIN_NAME_MAX 104Returns the size of the storage required for a login name, in bytes, 105including the terminating NUL. 106.It Li _SC_MAPPED_FILES 107Return 1 if the Memory Mapped Files Option is available on this system, 108otherwise \-1. 109.It Li _SC_MEMLOCK 110Return 1 if the Process Memory Locking Option is available on this system, 111otherwise \-1. 112.It Li _SC_MEMLOCK_RANGE 113Return 1 if the Range Memory Locking Option is available on this system, 114otherwise \-1. 115.It Li _SC_MEMORY_PROTECTION 116Return 1 if the Memory Protection Option is available on this system, 117otherwise \-1. 118.It Li _SC_MONOTONIC_CLOCK 119Return the 120.Tn POSIX 121version the implementation of the Monotonic Clock Option 122on this system conforms to, 123or \-1 if unavailable. 124.It Li _SC_NGROUPS_MAX 125The maximum number of supplemental groups. 126.It Li _SC_OPEN_MAX 127The maximum number of open files per process. 128.It Li _SC_PAGESIZE 129The size of a system page in bytes. 130.It Li _SC_PASS_MAX 131The maximum length of the password, not counting NULL. 132.It Li _SC_READER_WRITER_LOCKS 133The version of 134.St -p1003.1 135and its 136Read-Write Locks 137option to which the system attempts to conform, 138otherwise \-1. 139.It Li _SC_REGEXP 140Return 1 if 141.Tn POSIX 142regular expressions are available on this system, otherwise \-1. 143.It Li _SC_SEMAPHORES 144The version of 145.St -p1003.1 146and its 147Semaphores 148option to which the system attempts to conform, 149otherwise \-1. 150.Pp 151Availability of the 152Semaphores 153option depends on the 154.Li P1003_1B_SEMAPHORE 155kernel option. 156.It Li _SC_SHELL 157Return 1 if 158.Tn POSIX 159shell is available on this system, otherwise \-1. 160.It Li _SC_SPIN_LOCKS 161The version of 162.St -p1003.1 163and its 164Spin Locks 165option to which the system attempts to conform, 166otherwise \-1. 167.It Li _SC_STREAM_MAX 168The minimum maximum number of streams that a process may have open 169at any one time. 170.It Li _SC_SYMLOOP_MAX 171The maximum number of symbolic links that may be expanded in a path name. 172.It Li _SC_SYNCHRONIZED_IO 173Return 1 if the Synchronized I/O Option is available on this system, 174otherwise \-1. 175.It Li _SC_THREADS 176The version of 177.St -p1003.1 178and its 179Threads 180option to which the system attempts to conform, 181otherwise \-1. 182.It Li _SC_TIMERS 183The version of 184.St -p1003.1 185and its 186Timers 187option to which the system attempts to conform, 188otherwise \-1. 189.It Li _SC_TZNAME_MAX 190The minimum maximum number of types supported for the name of a 191timezone. 192.It Li _SC_SAVED_IDS 193Returns 1 if saved set-group and saved set-user ID is available, 194otherwise \-1. 195.It Li _SC_VERSION 196The version of ISO/IEC 9945 (POSIX 1003.1) with which the system 197attempts to comply. 198.It Li _SC_XOPEN_SHM 199Return 1 if the 200.St -xpg4.2 201Shared Memory 202option is available on this system, 203otherwise \-1. 204.Pp 205Availability of the 206Shared Memory 207option depends on the 208.Li SYSVSHM 209kernel option. 210.It Li _SC_BC_BASE_MAX 211The maximum ibase/obase values in the 212.Xr bc 1 213utility. 214.It Li _SC_BC_DIM_MAX 215The maximum array size in the 216.Xr bc 1 217utility. 218.It Li _SC_BC_SCALE_MAX 219The maximum scale value in the 220.Xr bc 1 221utility. 222.It Li _SC_BC_STRING_MAX 223The maximum string length in the 224.Xr bc 1 225utility. 226.It Li _SC_COLL_WEIGHTS_MAX 227The maximum number of weights that can be assigned to any entry of 228the LC_COLLATE order keyword in the locale definition file. 229.It Li _SC_EXPR_NEST_MAX 230The maximum number of expressions that can be nested within 231parenthesis by the 232.Xr expr 1 233utility. 234.It Li _SC_LINE_MAX 235The maximum length in bytes of a text-processing utility's input 236line. 237.It Li _SC_RE_DUP_MAX 238The maximum number of repeated occurrences of a regular expression 239permitted when using interval notation. 240.It Li _SC_2_VERSION 241The version of POSIX 1003.2 with which the system attempts to comply. 242.It Li _SC_2_C_BIND 243Return 1 if the system's C-language development facilities support the 244C-Language Bindings Option, otherwise \-1. 245.It Li _SC_2_C_DEV 246Return 1 if the system supports the C-Language Development Utilities Option, 247otherwise \-1. 248.It Li _SC_2_CHAR_TERM 249Return 1 if the system supports at least one terminal type capable of 250all operations described in POSIX 1003.2, otherwise \-1. 251.It Li _SC_2_FORT_DEV 252Return 1 if the system supports the FORTRAN Development Utilities Option, 253otherwise \-1. 254.It Li _SC_2_FORT_RUN 255Return 1 if the system supports the FORTRAN Runtime Utilities Option, 256otherwise \-1. 257.It Li _SC_2_LOCALEDEF 258Return 1 if the system supports the creation of locales, otherwise \-1. 259.It Li _SC_2_SW_DEV 260Return 1 if the system supports the Software Development Utilities Option, 261otherwise \-1. 262.It Li _SC_2_UPE 263Return 1 if the system supports the User Portability Utilities Option, 264otherwise \-1. 265.It Li _SC_GETGR_R_SIZE_MAX 266The minimum size of the 267.Fa buffer 268passed to 269.Xr getgrgid_r 3 270and 271.Xr getgrnam_r 3 . 272.It Li _SC_GETPW_R_SIZE_MAX 273The minimum size of the 274.Fa buffer 275passed to 276.Xr getpwnam_r 3 277and 278.Xr getpwuid_r 3 . 279.It Li _SC_NPROCESSORS_CONF 280The number of processors configured. 281.It Li _SC_NPROCESSORS_ONLN 282The number of processors online (capable of running processes). 283.El 284.Sh RETURN VALUES 285If the call to 286.Nm sysconf 287is not successful, \-1 is returned and 288.Va errno 289is set appropriately. 290Otherwise, if the variable is associated with functionality that is not 291supported, \-1 is returned and 292.Va errno 293is not modified. 294Otherwise, the current variable value is returned. 295.Sh ERRORS 296The 297.Fn sysconf 298function may fail and set 299.Va errno 300for any of the errors specified for the library functions 301.Xr sysctl 3 . 302In addition, the following error may be reported: 303.Bl -tag -width Er 304.It Bq Er EINVAL 305The value of the 306.Fa name 307argument is invalid. 308.El 309.Sh SEE ALSO 310.Xr sysctl 3 311.Sh STANDARDS 312The 313.Fn sysconf 314function conforms to 315.St -p1003.1-90 . 316The constants 317.Li _SC_NPROCESSORS_CONF 318and 319.Li _SC_NPROCESSORS_ONLN 320are not part of the standard, but are provided by many systems. 321.Sh HISTORY 322The 323.Nm sysconf 324function first appeared in 325.Bx 4.4 . 326.Sh BUGS 327The value for _SC_STREAM_MAX is a minimum maximum, and required to be 328the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 329small and misleading number. 330