由于前几天升级了protoc的版本用于新项目，导致老项目的protoc版本不一致，偏偏这个老项目的protoc版本不能升级，所以需要安装指定版本的protoc。
但当去执行brew install protoc@v3.21.9的时候，提醒我这个版本已经不支持了。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 brew install protoc@v3.21.9 Running `brew update --auto-update`... ==> Auto-updated Homebrew! Updated 4 taps (shivammathur/php, homebrew/services, homebrew/core and homebrew/cask). ==> New Formulae cargo-sweep chisel-tunnel direwolf glbinding@2 redress ==> New Casks garmin-basecamp reader truhu You have 36 outdated formulae installed. Warning: No available formula with the name "protoc@v3.21.9". Did you mean protobuf@21? ==> Searching for similarly named formulae and casks... ==> Formulae protobuf@21 ✔ To install protobuf@21 ✔, run: brew install protobuf@21 ✔
后面找了很多方法，要么卸载后重新下载，走压缩安装的方式，哎我还就不信了，homebrew的方式不行吗？捣鼓了半天发现是可以的。
首先找到对应的要安装的链接，使用brew info protobuf
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Protocol buffers (Google's data interchange format) https://protobuf.dev/ /opt/homebrew/Cellar/protobuf/25.1 (458 files, 14.7MB) * Poured from bottle using the formulae.brew.sh API on 2023-12-08 at 17:15:54 From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/p/protobuf.rb License: BSD-3-Clause ==> Dependencies Build: cmake ✘, python-setuptools ✘, python@3.11 ✔, python@3.12 ✘ Required: abseil ✔, jsoncpp ✔ ==> Caveats Emacs Lisp files have been installed to: /opt/homebrew/share/emacs/site-lisp/protobuf ==> Analytics install: 60,227 (30 days), 177,592 (90 days), 498,980 (365 days) install-on-request: 29,124 (30 days), 83,154 (90 days), 229,480 (365 days) build-error: 14 (30 days)
拿到protobuf.rb 的地址为 https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/protobuf.rb, 找到history，选择自己需要的版本。protobuf.rb
然后执行brew install ./protobuf.rb，就可以安装指定版本的protoc了。如果有冲突，记得将已安装的高版本的protoc卸载掉。
