Problem install JSON on UBUNTU 18.04

[trocolit2]

Hi,
I installed a fresh new UBUNTU 18.04, and I am facing errors during json installation.
After ran the gem install json command I got the error shown in follow

$ sudo gem install json
Building native extensions. This could take a while...
ERROR:  Error installing json:
	ERROR: Failed to build gem native extension.

    current directory: /var/lib/gems/2.5.0/gems/json-2.1.0/ext/json/ext/generator
/usr/bin/ruby2.5 -r ./siteconf20180620-12452-uyviq.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/json-2.1.0 for inspection.
Results logged to /var/lib/gems/2.5.0/extensions/x86_64-linux/2.5.0/json-2.1.0/gem_make.out

For Ubuntu 18.04, the ruby version is 2.5.
Could any one gives me tips to solve this issue?
I can provide more detailed information if needed.

Thanks in advance.

[guygastineau]

You should be able to require 'json' at the top of your file without installing any gems.

If you do need the gem for some reason

• I don't think you need to use sudo to execute gem install json

• Did you try it without sudo?

[guygastineau]

• Seeing the contents of that gem_make.out file where the results were logged would be really helpful.

[jmcclare]

I had the same issue on Ubuntu 18.04. From what I can tell this is not an issue with the JSON Ruby gem. This is more of a documentation and Ruby system setup issue.

You need to install the ruby-dev package to get the header files it’s looking for.

Do the following.

sudo apt install -y ruby-dev
sudo gem install json

It should install and build its extensions without issue.

Installing ruby-dev should be in the standard instructions for setting up Ruby on Ubuntu.