1.\" Copyright (c) 1983, 1991, 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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" from: @(#)getdtablesize.2 8.1 (Berkeley) 6/4/93 29.\" $NetBSD: getdtablesize.3,v 1.14 2012/01/05 07:05:59 yamt Exp $ 30.\" 31.Dd January 5, 2012 32.Dt GETDTABLESIZE 3 33.Os 34.Sh NAME 35.Nm getdtablesize 36.Nd get descriptor table size 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft int 42.Fn getdtablesize void 43.Sh DESCRIPTION 44The 45.Nm 46function is an equivalent of 47.Fn sysconf 48with 49.Dv _SC_OPEN_MAX . 50.Sh SEE ALSO 51.Xr close 2 , 52.Xr dup 2 , 53.Xr getrlimit 2 , 54.Xr open 2 , 55.Xr select 2 , 56.Xr sysconf 3 57.Sh HISTORY 58The 59.Fn getdtablesize 60function call appeared in 61.Bx 4.2 . 62.Pp 63Historically, each process had a fixed size descriptor table, 64which is guaranteed to have at least 20 slots. 65The entries in 66the descriptor table are numbered with small integers starting at 0. 67The call 68.Fn getdtablesize 69used to return the size of this table. 70It doesn't make much sense these days because the size of the table is dynamic. 71