1.\" Copyright (c) 2008 Yahoo!, Inc. 2.\" All rights reserved. 3.\" Written by: John Baldwin <jhb@FreeBSD.org> 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. Neither the name of the author nor the names of any co-contributors 14.\" may be used to endorse or promote products derived from this software 15.\" without specific prior written permission. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.Dd January 8, 2008 30.Dt FEATURE_PRESENT 3 31.Os 32.Sh NAME 33.Nm feature_present 34.Nd query presence of a kernel feature 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In unistd.h 39.Ft int 40.Fn feature_present "const char *feature" 41.Sh DESCRIPTION 42The 43.Fn feature_present 44function provides a method for an application to determine if a specific 45kernel feature is present in the currently running kernel. 46The 47.Fa feature 48argument specifies the name of the feature to check. 49The 50.Fn feature_present 51function will return 1 if the specified feature is present, 52otherwise it will return 0. 53If the 54.Fn feature_present 55function is not able to determine the presence of 56.Fa feature 57due to an internal error it will return 0. 58.Sh RETURN VALUES 59If 60.Fa feature 61is present then 1 is returned; 62otherwise 0 is returned. 63.Sh SEE ALSO 64.Xr sysconf 3 , 65.Xr sysctl 3 66.Sh HISTORY 67The 68.Fn feature_present 69function first appeared in 70.Fx 8.0 . 71