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--- os:linux:file_watcher_service [2020-12-05 00:49] – created Manuel Frei
+++ os:linux:file_watcher_service [2020-12-05 11:30] (current) – Manuel Frei
@@ Line 16: / Line 16: @@
 #!/usr/bin/env bash
 file_name="/tmp/watched_file.txt"
-log_file="/tmp/$(basename ${0}).log"
+log_file="/tmp/$(basename "${0}").log"
+lock_file="/tmp/$(basename "${0}").lock"
+# check & set lock
+exec 200>${lock_file}
+flock -n 200 || { echo "Another instance of this script is already running. Abort."; exit 1; }
+PID=$$
+echo ${PID} 1>&200
+# file watch
 while true; do
     inotifywait -e modify ${file_name}
     echo "[$(date --iso-8601=seconds)] change detected on file ${file_name}" >> ${log_file}
-    # maybe do some other actions
+    # maybe do some other actions after a modification
 done
 </code>
@@ Line 49: / Line 58: @@
 systemctl daemon-reload
 systemctl start file_watcher.service
+</code>
+If you need to create some form of monitoring script/actions, maybe this snippets will help you:
+<code>
+[root@server ~]# systemctl is-active file_watcher.service >/dev/null && echo OK || echo NOK
+OK
+[root@server ~]# systemctl stop file_watcher.service
+[root@server ~]# systemctl is-active file_watcher.service >/dev/null && echo OK || echo NOK
+NOK
 </code>