What enviroment variables should be set when using ruby?

[ssxcxS45XT]

Here is the output of brew info ruby. It is clear that PATH will need to be set.

But what about LDFLAGS, CPPFLAGS and PKG_CONFIG_PATH? If they are set, will they cause any conflict when other package (may or may not be homebrew packages need to use the native ruby on Mac OS X)? Thanks.

$ brew info ruby
ruby: stable 3.0.0 (bottled), HEAD [keg-only]
Powerful, clean, object-oriented scripting language
https://www.ruby-lang.org/
/usr/local/Cellar/ruby/3.0.0_1 (16,314 files, 37.6MB)
  Poured from bottle on 2021-01-01 at 19:10:16
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/ruby.rb
License: Ruby
==> Dependencies
Build: pkg-config ✔
Required: libyaml ✔, [email protected] ✔, readline ✔
==> Options
--HEAD
	Install HEAD version
==> Caveats
By default, binaries installed by gem will be placed into:
  /usr/local/lib/ruby/gems/3.0.0/bin

You may want to add this to your PATH.

ruby is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.

If you need to have ruby first in your PATH run:
  echo 'export PATH="/usr/local/opt/ruby/bin:$PATH"' >> /Users/pengy/.bash_profile

For compilers to find ruby you may need to set:
  export LDFLAGS="-L/usr/local/opt/ruby/lib"
  export CPPFLAGS="-I/usr/local/opt/ruby/include"

For pkg-config to find ruby you may need to set:
  export PKG_CONFIG_PATH="/usr/local/opt/ruby/lib/pkgconfig"

==> Analytics
install: 122,704 (30 days), 317,699 (90 days), 1,033,544 (365 days)
install-on-request: 76,334 (30 days), 207,237 (90 days), 599,276 (365 days)
build-error: 0 (30 days)

[carlocab]

You need to set LDFLAGS, CPPFLAGS, and PKG_CONFIG_PATH only if you are compiling software outside of Homebrew that use Homebrew ruby.

If you're not sure, it's likely that you are not doing this, in which case there is no need for you to set these variables.