"arduino.h: No such file or directory" Ubuntu

I have error in linux environment, Ubuntu 18.04.4, on Windows works well. I have no idea how fix it and where to check ... Before I install the IDE though install.sh from git

Did you install from the Ubuntu repository? If so, download from this website; the repository is severely outdated.

Are you trying to compile for an Arduino? Or for something else (e.g. for ESP)?

I think that it's Arduino.h, note the capital.

I guess that the images are screenshots of errors; if so, please don't but copy/paste the text here.

Change this line:

#include <arduino.h>

to:

#include <Arduino.h>

Linux is filename case sensitive. Windows is filename case insensitive.

Note that it's actually not necessary to add an #include directive for Arduino.h to your sketch. The Arduino development software automatically adds this #include directive to the .ino files of all sketches. You only need to add this #include directive to .h, .c, or .cpp files that reference parts of the standard Arduino API (because, unlike .ino files, no sketch preprocessing is done on those file types).

sterretje:
I think that it's Arduino.h, note the capital.

Yes! I would like to kill myself for inattention ))

pert:
Linux is filename case sensitive. Windows is filename case insensitive.

I did it, Thanx !