This means that even simple POSIX fish taco recipe scripts may require some significant adaptation or even full rewriting to run with fish. Once installed, simply type fish to drop into the fish shell.

It is recommended to read at least the “Syntax overview” section, since fish’s syntax is different from many other shells. One must decide whether fish is going to be the default user’s shell, which means that the user falls directly in fish at login, or whether it is used in interactive terminal mode as a child process of the current default shell, here we will assume the latter is Bash. The user’s current initialization scripts and environment variables need to be migrated to the new fish environment. Bash initialization scripts are run as usual and fish runs on top of Bash in interactive mode connected to a terminal.

Setting fish as interactive shell only. PATH environment variable, once directly logged under fish, should be checked and adjusted to one’s need. PATH is defined as a global environment variable: it has a global scope across all functions, it is lost upon reboot and it is an environment variable which means it is exported to child processes. These three locations will be prepended to the path. Not setting fish as system wide or user default allows the current Bash scripts to run on startup.