fish1 is a smart and user-friendly command line shell for macOS, Linux, and the rest of the family. fish includes features like syntax highlighting, autosuggest-as-you-type, and fancy tab completions that just work, with no configuration required.
fish generally works like other shells, like bash or zsh. A few important differences can be found in the tutorials by searching for the magic phrase "unlike other shells".
If you wish to use fish as your default shell, use the following command:
chsh -s /usr/local/bin/fish
chsh will prompt you for your password, and change your default shell. Substitute /usr/local/bin/fish with whatever path to fish is in your /etc/shells file.
Use the following command if you didn't already add your fish path to /etc/shells.
echo /usr/local/bin/fish | sudo tee -a /etc/shells
To switch your default shell back, you can run:
chsh -s /bin/bash
Substitute /bin/bash with /bin/ksh or /bin/zsh as appropriate.
You may need to logout/login for the change (chsh) to take effect.
[1^]:fish is provided under the GNU Public License v2.