gem でnokogiri がinstallできないとき
$ sudo gem install nokogiri
でnokogiriがインストールできない時、
$ sudo apt-get install zlib1g-dev
ってしたらいいですよ。
エラーは以下の通り。
Building native extensions. This could take a while... ERROR: Error installing nokogiri: ERROR: Failed to build gem native extension. current directory: /var/lib/gems/2.3.0/gems/nokogiri-1.8.1/ext/nokogiri /usr/bin/ruby2.3 -r ./siteconf20171123-16896-1j95jcs.rb extconf.rb checking if the C compiler accepts ... yes Building nokogiri using packaged libraries. Using mini_portile version 2.3.0 checking for gzdopen() in -lz... no zlib is missing; necessary for building libxml2 *** 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=/usr/bin/$(RUBY_BASE_NAME)2.3 --help --clean --use-system-libraries --enable-static --disable-static --with-zlib-dir --without-zlib-dir --with-zlib-include --without-zlib-include=${zlib-dir}/include --with-zlib-lib --without-zlib-lib=${zlib-dir}/lib --enable-cross-build --disable-cross-build To see why this extension failed to compile, please check the mkmf.log which can be found here: /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/nokogiri-1.8.1/mkmf.log extconf failed, exit code 1 Gem files will remain installed in /var/lib/gems/2.3.0/gems/nokogiri-1.8.1 for inspection. Results logged to /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/nokogiri-1.8.1/gem_make.out