Cant' open lib libdemoabc.so

Sometimes your run into this error for Linux applications:
    Can't open lib /usr/abc/libdemoabc.so
The above error message is quite misleading. Actually the lib does exist. but some of its dependent libs are missing. Setting up the LD_LIBRARY_PATH solves the problem.

Watch files in a directory

Linux: inotifywatch in inotify-tools
Windows: FileSystemWatcher

Reference:
https://www.howtogeek.com/405468/how-to-perform-a-task-when-a-new-file-is-added-to-a-directory-in-linux/
https://gallery.technet.microsoft.com/scriptcenter/Powershell-FileSystemWatche-dfd7084b