Be robust to a bogus script specification or contents

when figuring out what the real interpreter is for an
interpreted command.  That is, check whether we can read
the script file in the first place and, if so, make sure
we got a valid shebang line from it.

etc/rc.subr

@@ -283,17 +283,30 @@ _find_processes()
 
 	_pref=
 	if [ $_interpreter != "." ]; then	# an interpreted script
-						# read interpreter name
-		read _interp < ${_chroot}${_chroot:+"/"}$_procname
-		_interp=${_interp#\#!}		# strip #!
-		set -- $_interp
-		case $1 in
-		*/bin/env)
-			shift			# drop env to get real name
-			;;
-		esac
-		if [ $_interpreter != $1 ]; then
-			warn "\$command_interpreter $_interpreter != $1"
+		_script=${_chroot}${_chroot:+"/"}$_procname
+		if [ -r $_script ]; then
+			read _interp < $_script	# read interpreter name
+			case "$_interp" in
+			\#!*)
+				_interp=${_interp#\#!}	# strip #!
+				set -- $_interp
+				case $1 in
+				*/bin/env)
+					shift	# drop env to get real name
+					;;
+				esac
+				if [ $_interpreter != $1 ]; then
+					warn "\$command_interpreter $_interpreter != $1"
+				fi
+				;;
+			*)
+				warn "no shebang line in $_script"
+				set -- $_interpreter
+				;;
+			esac
+		else
+			warn "cannot read shebang line from $_script"
+			set -- $_interpreter
 		fi
 		_interp="$* $_procname"		# cleanup spaces, add _procname
 		_interpbn=${1##*/}