sudo apt-get install ruby2.3-dev
this was successful
but this was not
pi@raspberrypi:~/Cellar $ sudo gem install smashing
Building native extensions. This could take a while...
ERROR: Error installing smashing:
ERROR: Failed to build gem native extension.
current directory: /var/lib/gems/2.5.0/gems/eventmachine-1.2.7/ext
/usr/bin/ruby2.5 -r ./siteconf20200621-23957-f66zcs.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h
extconf failed, exit code 1
Gem files will remain installed in /var/lib/gems/2.5.0/gems/eventmachine-1.2.7 for inspection.
Results logged to /var/lib/gems/2.5.0/extensions/arm-linux/2.5.0/eventmachine-1.2.7/gem_make.out
I see that although ruby2.3 was installed it seems to have installed Gems 2.5
sudo apt-get install ruby2.3-dev
this was successful
but this was not
pi@raspberrypi:~/Cellar $ sudo gem install smashing
Building native extensions. This could take a while...
ERROR: Error installing smashing:
ERROR: Failed to build gem native extension.
/usr/bin/ruby2.5 -r ./siteconf20200621-23957-f66zcs.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h
extconf failed, exit code 1
Gem files will remain installed in /var/lib/gems/2.5.0/gems/eventmachine-1.2.7 for inspection.
Results logged to /var/lib/gems/2.5.0/extensions/arm-linux/2.5.0/eventmachine-1.2.7/gem_make.out
I see that although ruby2.3 was installed it seems to have installed Gems 2.5