tl;dr mojave or lower sudo gem install cocoapods -n /usr/local/binしような。 たぶんmojaveでもおなじです。High sierraでインストールして、mojaveへアップグレードした場合はそのまま使えるようです。 Catalina or higher Catalina(macOS 10.15)では sudo gem install cocoapods でインストールができるようです。 概要 macOSX Highsierra上にて、sudo gem upgrade --systemして、sudo gem install cocoapodsでインストールしようとしたところ失敗したのでなんとかした。 詳細 $ sudo gem install cocoapods Fetching: concurrent-ruby-1.0.5
![High sierraからmojaveまでのバージョンでCocoapodsがインストールできなかったのを解消 - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/fede70ca4da0c6765cbf71e5179d3bf9d0975c17/height=288;version=1;width=512/https%3A%2F%2Fqiita-user-contents.imgix.net%2Fhttps%253A%252F%252Fcdn.qiita.com%252Fassets%252Fpublic%252Farticle-ogp-background-1150d8b18a7c15795b701a55ae908f94.png%3Fixlib%3Drb-1.2.2%26w%3D1200%26mark%3Dhttps%253A%252F%252Fqiita-user-contents.imgix.net%252F~text%253Fixlib%253Drb-1.2.2%2526w%253D840%2526h%253D380%2526txt%253DHigh%252520sierra%2525E3%252581%25258B%2525E3%252582%252589mojave%2525E3%252581%2525BE%2525E3%252581%2525A7%2525E3%252581%2525AE%2525E3%252583%252590%2525E3%252583%2525BC%2525E3%252582%2525B8%2525E3%252583%2525A7%2525E3%252583%2525B3%2525E3%252581%2525A7Cocoapods%2525E3%252581%25258C%2525E3%252582%2525A4%2525E3%252583%2525B3%2525E3%252582%2525B9%2525E3%252583%252588%2525E3%252583%2525BC%2525E3%252583%2525AB%2525E3%252581%2525A7%2525E3%252581%25258D%2525E3%252581%2525AA%2525E3%252581%25258B%2525E3%252581%2525A3%2525E3%252581%25259F%2525E3%252581%2525AE%2525E3%252582%252592%2525E8%2525A7%2525A3%2525E6%2525B6%252588%2526txt-color%253D%252523333%2526txt-font%253DHiragino%252520Sans%252520W6%2526txt-size%253D54%2526txt-clip%253Dellipsis%2526txt-align%253Dcenter%25252Cmiddle%2526s%253Debb077aa0714ff0e2d09b1e5fbfe70f6%26mark-align%3Dcenter%252Cmiddle%26blend%3Dhttps%253A%252F%252Fqiita-user-contents.imgix.net%252F~text%253Fixlib%253Drb-1.2.2%2526w%253D840%2526h%253D500%2526txt%253D%252540usagisystem%2526txt-color%253D%252523333%2526txt-font%253DHiragino%252520Sans%252520W6%2526txt-size%253D45%2526txt-align%253Dright%25252Cbottom%2526s%253D16e0bc758ec12ccd05fa2961c16b65c4%26blend-align%3Dcenter%252Cmiddle%26blend-mode%3Dnormal%26s%3D2800598a1fd9fe2b338e3accc87c0a73)