Add new rc keywords: enable, disable, delete

This adds new keywords to rc/service to enable/disable a service's
rc.conf(5) variable and "delete" to remove the variable.

When the "service_delete_empty" variable in rc.conf(5) is set to "YES"
(default is "NO") an rc.conf.d file (in /etc/ or /usr/local/etc) is
deleted if empty after modification using "service $foo delete".

Submitted by:	lme (modified)
Reviewed by:	0mp (previous version), lme, bcr
Relnotes:	yes
Sponsored by:	Smule, Inc.
Differential Revision:	https://reviews.freebsd.org/D17113

libexec/rc/rc.conf

@@ -617,6 +617,7 @@ savecore_enable="YES"	# Extract core from dump devices if any
 savecore_flags="-m 10"	# Used if dumpdev is enabled above, and present.
 			# By default, only the 10 most recent kernel dumps
 			# are saved.
+service_delete_empty="NO" # Have 'service delete' remove empty rc.conf.d files.
 crashinfo_enable="YES"	# Automatically generate crash dump summary.
 crashinfo_program="/usr/sbin/crashinfo"	# Script to generate crash dump summary.
 quota_enable="NO"	# turn on quotas on startup (or NO).

libexec/rc/rc.subr

@@ -922,7 +922,7 @@ run_rc_command()
 	eval _override_command=\$${name}_program
 	command=${_override_command:-$command}
 
-	_keywords="start stop restart rcvar enabled describe extracommands $extra_commands"
+	_keywords="start stop restart rcvar enable disable delete enabled describe extracommands $extra_commands"
 	rc_pid=
 	_pidcmd=
 	_procname=${procname:-${command}}
@@ -977,12 +977,13 @@ run_rc_command()
 		if [ "$_elem" != "$rc_arg" ]; then
 			continue
 		fi
-					# if ${rcvar} is set, $1 is not "rcvar" and not "describe"
-					# and ${rc_pid} is not set, then run
+					# if ${rcvar} is set, $1 is not "rcvar", "describe",
+					# "enable" or "delete", and ${rc_pid} is not set, run:
 					#	checkyesno ${rcvar}
 					# and return if that failed
 					#
 		if [ -n "${rcvar}" -a "$rc_arg" != "rcvar" -a "$rc_arg" != "stop" \
+		    -a "$rc_arg" != "delete" -a "$rc_arg" != "enable" \
 		    -a "$rc_arg" != "describe" ] ||
 		    [ -n "${rcvar}" -a "$rc_arg" = "stop" -a -z "${rc_pid}" ]; then
 			if ! checkyesno ${rcvar}; then
@@ -1030,6 +1031,31 @@ run_rc_command()
 			echo "$extra_commands"
 			;;
 
+		enable)
+			_out=$(/usr/sbin/sysrc -vs "$name" "$rcvar=YES") &&
+				echo "$name enabled in ${_out%%:*}"	
+			;;
+
+		disable)
+			_out=$(/usr/sbin/sysrc -vs "$name" "$rcvar=NO") &&
+				echo "$name disabled in ${_out%%:*}"	
+			;;
+
+		delete)
+			_files=
+			for _file in $(sysrc -lEs "$name"); do
+				_out=$(sysrc -Fif $_file "$rcvar") && _files="$_files $_file"
+			done
+			/usr/sbin/sysrc -x "$rcvar" && echo "$rcvar deleted in ${_files# }"
+				# delete file in rc.conf.d if desired and empty.
+			checkyesno service_delete_empty || _files=
+			for _file in $_files; do
+				[ "$_file" = "${_file#*/rc.conf.d/}" ] && continue
+				[ $(/usr/bin/stat -f%z $_file) -gt 0 ] && continue
+				/bin/rm "$_file" && echo "Empty file $_file removed"
+			done
+			;;
+
 		status)
 			_run_rc_precmd || return 1
 			if [ -n "$rc_pid" ]; then

share/man/man5/rc.conf.5

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 22, 2018
+.Dd October 24, 2018
 .Dt RC.CONF 5
 .Os
 .Sh NAME
@@ -4509,6 +4509,14 @@ at boot time.
 The directory where the files exported by USB LUN are located.
 The default directory is
 .Pa /var/cfumass .
+.It Va service_delete_empty
+.Pq Vt bool
+If set to
+.Dq Li YES ,
+.Ql Li service delete
+removes empty
+.Dq Li rc.conf.d
+files.
 .El
 .Sh FILES
 .Bl -tag -width ".Pa /etc/defaults/rc.conf" -compact
@@ -4597,6 +4605,7 @@ The default directory is
 .Xr rwhod 8 ,
 .Xr savecore 8 ,
 .Xr sdpd 8 ,
+.Xr service 8 ,
 .Xr sshd 8 ,
 .Xr swapon 8 ,
 .Xr sysctl 8 ,

share/man/man8/rc.8

@@ -31,7 +31,7 @@
 .\"     @(#)rc.8	8.2 (Berkeley) 12/11/93
 .\" $FreeBSD$
 .\"
-.Dd April 25, 2017
+.Dd September 18, 2018
 .Dt RC 8
 .Os
 .Sh NAME
@@ -327,6 +327,21 @@ If the script starts a process (rather than performing a one-off
 operation), show the status of the process.
 Otherwise it is not necessary to support this argument.
 Defaults to displaying the process ID of the program (if running).
+.It Cm enable
+Enable the service in
+.Xr rc.conf 5 .
+.It Cm disable
+Disable the service in
+.Xr rc.conf 5 .
+.It Cm delete
+Remove the service from
+.Xr rc.conf 5 .
+If
+.Ql Li service_delete_empty
+is set to
+.Dq Li YES ,
+.Pa /etc/rc.conf.d/$servicename
+will be deleted if empty after modification.
 .It Cm describe
 Print a short description of what the script does.
 .It Cm extracommands