shell

https://en.wikipedia.org/wiki/Comparison_of_command_shells

bash

• https://en.wikipedia.org/wiki/Bash_(Unix_shell)
• https://www.gnu.org/software/bash/
• https://git.savannah.gnu.org/cgit/bash.git/refs/
• https://github.com/bminor/bash
• https://www.gnu.org/software/bash/manual/bash.html

zsh

• https://en.wikipedia.org/wiki/Z_shell
• https://www.zsh.org
• https://sourceforge.net/p/zsh/code/ci/master/tree/
• https://github.com/zsh-users/zsh
• https://zsh.sourceforge.io/Doc/Release/