Add a feature_present(3) function which checks to see if a named kernel
feature is present by checking the kern.features sysctl MIB. MFC after: 1 week
This commit is contained in:
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=175220
@ -480,6 +480,7 @@ int des_setkey(const char *key);
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void endusershell(void);
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void endusershell(void);
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int exect(const char *, char * const *, char * const *);
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int exect(const char *, char * const *, char * const *);
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int execvP(const char *, const char *, char * const *);
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int execvP(const char *, const char *, char * const *);
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int feature_present(const char *);
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char *fflagstostr(u_long);
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char *fflagstostr(u_long);
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int getdomainname(char *, int);
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int getdomainname(char *, int);
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int getgrouplist(const char *, gid_t, gid_t *, int *);
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int getgrouplist(const char *, gid_t, gid_t *, int *);
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@ -10,7 +10,7 @@ SRCS+= __getosreldate.c __xuname.c \
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clock.c closedir.c confstr.c \
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clock.c closedir.c confstr.c \
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crypt.c ctermid.c daemon.c devname.c dirname.c disklabel.c \
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crypt.c ctermid.c daemon.c devname.c dirname.c disklabel.c \
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dlfcn.c dlfunc.c drand48.c erand48.c err.c errlst.c errno.c \
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dlfcn.c dlfunc.c drand48.c erand48.c err.c errlst.c errno.c \
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exec.c fmtcheck.c fmtmsg.c fnmatch.c \
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exec.c feature_present.c fmtcheck.c fmtmsg.c fnmatch.c \
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fpclassify.c frexp.c fstab.c ftok.c fts.c ftw.c \
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fpclassify.c frexp.c fstab.c ftok.c fts.c ftw.c \
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getbootfile.c getbsize.c \
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getbootfile.c getbsize.c \
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getcap.c getcwd.c getdomainname.c getgrent.c getgrouplist.c \
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getcap.c getcwd.c getdomainname.c getgrent.c getgrouplist.c \
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@ -45,7 +45,8 @@ MAN+= alarm.3 arc4random.3 \
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basename.3 check_utility_compat.3 clock.3 \
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basename.3 check_utility_compat.3 clock.3 \
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confstr.3 ctermid.3 daemon.3 devname.3 directory.3 dirname.3 \
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confstr.3 ctermid.3 daemon.3 devname.3 directory.3 dirname.3 \
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dladdr.3 dlinfo.3 dllockinit.3 dlopen.3 \
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dladdr.3 dlinfo.3 dllockinit.3 dlopen.3 \
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err.3 exec.3 fmtcheck.3 fmtmsg.3 fnmatch.3 fpclassify.3 frexp.3 \
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err.3 exec.3 \
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feature_present.3 fmtcheck.3 fmtmsg.3 fnmatch.3 fpclassify.3 frexp.3 \
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ftok.3 fts.3 ftw.3 \
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ftok.3 fts.3 ftw.3 \
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getbootfile.3 getbsize.3 getcap.3 getcontext.3 getcwd.3 \
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getbootfile.3 getbsize.3 getcap.3 getcontext.3 getcwd.3 \
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getdiskbyname.3 getdomainname.3 getfsent.3 \
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getdiskbyname.3 getdomainname.3 getfsent.3 \
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72
lib/libc/gen/feature_present.3
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72
lib/libc/gen/feature_present.3
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@ -0,0 +1,72 @@
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.\" Copyright (c) 2008 Yahoo!, Inc.
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.\" All rights reserved.
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.\" Written by: John Baldwin <jhb@FreeBSD.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the author nor the names of any co-contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 8, 2008
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.Dt feature_present 3
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.Os
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.Sh NAME
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.Nm feature_present
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.Nd query presence of a kernel feature
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn feature_present "const char *feature"
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.Sh DESCRIPTION
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The
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.Fn feature_present
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function provides a method for an application to determine if a specific
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kernel feature is present in the currently running kernel.
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The
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.Fa feature
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argument specifies the name of the feature to check.
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The
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.Fn feature_present
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function will return 1 if the specified feature is present,
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otherwise it will return 0.
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If the
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.Fn feature_present
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function is not able to determine the presence of
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.Fa feature
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due to an internal error it will return 0.
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.Sh RETURN VALUES
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If
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.Fa feature
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is present then 1 is returned;
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otherwise 0 is returned.
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.Sh SEE ALSO
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.Xr sysconf 3 ,
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.Xr sysctl 3
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.Sh HISTORY
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The
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.Fn feature_present
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function first appeared in
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.Fx 8.0 .
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62
lib/libc/gen/feature_present.c
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62
lib/libc/gen/feature_present.c
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@ -0,0 +1,62 @@
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/*-
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* Copyright (c) 2008 Yahoo!, Inc.
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* All rights reserved.
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* Written by: John Baldwin <jhb@FreeBSD.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/sysctl.h>
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#include <stdio.h>
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#include <stdlib.h>
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/*
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* Returns true if the named feature is present in the currently
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* running kernel. A feature's presence is indicated by an integer
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* sysctl node called kern.feature.<feature> that is non-zero.
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*/
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int
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feature_present(const char *feature)
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{
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char *mib;
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size_t len;
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int i;
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if (asprintf(&mib, "kern.features.%s", feature) < 0)
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return (0);
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len = sizeof(i);
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if (sysctlbyname(mib, &i, &len, NULL, 0) < 0) {
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free(mib);
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return (0);
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}
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free(mib);
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if (len != sizeof(i))
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return (0);
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return (i != 0);
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}
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