Unable to start uiautomatorviewer

Please note that uiautomatorviewer executable has been moved in SDK Tools Revision 25.3.0 update (Feb 2017) to new location under <android-sdk>\tools\bin

Navigate to tools folder, then launch terminal, launch monitor(Android Device Monitor) using ./monitor command.

ADM will get launched, left side of the window you may find .

Because your tools/ directory is not in your PATH. Either use ./uiautomatorviewer or add tools/ (and probably platform-tools/ to your PATH. Note that this has nothing to do with programming and everything to do with your *nix-style OS (Linux, OS X, etc.).