add serv exists for check of service existence

bin/serv

@@ -145,6 +145,7 @@ set_service_type
 
 verbose=
 quiet=
+short=
 non_interactive=
 show_command_only=
 serv_cmd=
@@ -194,6 +195,9 @@ check_command()
     cat)                      # HELPCMD: print out service file for the service
         serv_cmd=cat
         ;;
+    exists)                   # HELPCMD: check if the service is installed on the system
+        serv_cmd=exists
+        ;;
     edit)                     # HELPCMD: edit service file overload (use --full to edit full file)
         serv_cmd=edit
         ;;

bin/serv-exists

+#!/bin/sh
+#
+# Copyright (C) 2021  Etersoft
+# Copyright (C) 2021  Vitaly Lipatov <lav@etersoft.ru>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+serv_exists()
+{
+	local SERVICE="$1"
+	shift
+
+	case $SERVICETYPE in
+		systemd)
+			# too direct way: test -s /lib/systemd/system/dm.service
+			docmd systemctl cat "$SERVICE" "$@" >/dev/null 2>/dev/null
+			;;
+		*)
+			case $DISTRNAME in
+			ALTLinux)
+				local INITFILE=/etc/init.d/$SERVICE
+				[ -r "$INITFILE" ] || return
+				return ;;
+			*)
+				fatal "Have no suitable for $DISTRNAME command for $SERVICETYPE"
+				;;
+			esac
+	esac
+}