$ rails new i\_want\_to\_use\_mysql -d mysql 

$ rails new i\_want\_to\_use\_mysql -d mysql （中略） Installing mysql2 0.5.2 with native extensions Gem::Ext::BuildError: ERROR: Failed to build gem native extension. current directory: /Users/aksk/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.2/ext/mysql2 /Users/aksk/.rbenv/versions/2.6.3/bin/ruby -I /Users/aksk/.rbenv/versions/2.6.3/lib/ruby/2.6.0 -r ./siteconf20190822-76368-1osl1a0.rb extconf.rb checking for rb\_absint\_size()... yes checking for rb\_absint\_singlebit\_p()... yes checking for rb\_wait\_for\_single\_fd()... yes checking for -lmysqlclient... no ----- mysql client is missing. You may need to 'brew install mysql' or 'port install mysql', and try again. ----- \*\*\* extconf.rb failed \*\*\* Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/Users/aksk/.rbenv/versions/2.6.3/bin/$(RUBY\_BASE\_NAME) --with-mysql-dir --without-mysql-dir --with-mysql-include --without-mysql-include=${mysql-dir}/include --with-mysql-lib --without-mysql-lib=${mysql-dir}/lib --with-mysql-config --without-mysql-config --with-mysql-dir --without-mysql-dir --with-mysql-include --without-mysql-include=${mysql-dir}/include --with-mysql-lib --without-mysql-lib=${mysql-dir}/lib --with-mysqlclientlib --without-mysqlclientlib To see why this extension failed to compile, please check the mkmf.log which can be found here: /Users/aksk/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/extensions/x86\_64-darwin-18/2.6.0-static/mysql2-0.5.2/mkmf.log extconf failed, exit code 1 Gem files will remain installed in /Users/aksk/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/mysql2-0.5.2 for inspection. Results logged to /Users/aksk/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/extensions/x86\_64-darwin-18/2.6.0-static/mysql2-0.5.2/gem\_make.out An error occurred while installing mysql2 (0.5.2), and Bundler cannot continue. Make sure that `gem install mysql2 -v '0.5.2' --source 'https://rubygems.org/'` succeeds before bundling. In Gemfile: mysql2 run bundle exec spring binstub --all Could not find gem 'mysql2 (\>= 0.4.4, \< 0.6.0)' in any of the gem sources listed in your Gemfile. Run `bundle install` to install missing gems.

$ brew info openssl

openssl: stable 1.0.2s (bottled) [keg-only] SSL/TLS cryptography library https://openssl.org/ /usr/local/Cellar/openssl/1.0.2s (1,795 files, 12.0MB) Poured from bottle on 2019-07-25 at 18:36:37 From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/openssl.rb ==\> Caveats A CA file has been bootstrapped using certificates from the SystemRoots keychain. To add additional certificates (e.g. the certificates added in the System keychain), place .pem files in /usr/local/etc/openssl/certs and run /usr/local/opt/openssl/bin/c\_rehash openssl is keg-only, which means it was not symlinked into /usr/local, because Apple has deprecated use of OpenSSL in favor of its own TLS and crypto libraries. If you need to have openssl first in your PATH run: echo 'export PATH="/usr/local/opt/openssl/bin:$PATH"' \>\> ~/.zshrc For compilers to find openssl you may need to set: export LDFLAGS="-L/usr/local/opt/openssl/lib" export CPPFLAGS="-I/usr/local/opt/openssl/include" For pkg-config to find openssl you may need to set: export PKG\_CONFIG\_PATH="/usr/local/opt/openssl/lib/pkgconfig" ==\> Analytics install: 502,127 (30 days), 1,741,224 (90 days), 6,608,463 (365 days) install\_on\_request: 60,851 (30 days), 232,924 (90 days), 888,787 (365 days) build\_error: 0 (30 days)

 export LDFLAGS="-L/usr/local/opt/openssl/lib" export CPPFLAGS="-I/usr/local/opt/openssl/include"

$ bundle config --local build.mysql2 "--with-cppflags=-I/usr/local/opt/openssl/include" $ bundle config --local build.mysql2 "--with-ldflags=-L/usr/local/opt/openssl/lib"

$ rails new i\_want\_to\_use\_mysql -d mysql