macOS Login Shells

Ghostty respects the macOS traditions and will start each shell as a login shell. This matches the behavior of other terminal emulators on macOS, most notably the default Terminal.app. However, this behavior is different from other Unix systems, and may cause confusion for users who are used to the behavior of those systems.

Traditionally, unix shells have two main files that expect to be run before the user is able to interact with the shell: a profile file and the rc file. The profile file is usually run once at login and is used to set up the environment for the user. The rc file is run every time a new shell is created and is used to set up the shell itself.

Using zsh as an example (the default shell on macOS since 10.15): zsh uses the .zprofile and .zshrc files. On most Linux systems .zprofile (or similar) is executed when the user initially logs in via something like a desktop manager. This allows subsequent shells to inherit the environment and any setup done by .zprofile. The idea here is that any expensive initialization only needs done once at login, and subsequent shells can reuse everything from the setup process.

Note

Zsh is used as an example but almost any shell can be used in its place and have the same behavior, with the exception of bash. Bash will only read .bashrc if the shell is both interactive and non-login. Since macOS moved from tcsh to bash in OSX 10.2 Jaguar, this difference in bash may have been overlooked, resulting in developers placing their shell setup entirely in .profile as .bashrc would rarely be run, specifically not by starting a new terminal. Now that zsh is the new default, .zprofile and .zshrc are both called starting an interactive non-login shell.

macOS differs in that the GUI used to login to the system does not run .zprofile as it has its own method of loading in system level global settings. This means that any terminal emulator must run shells as login or else new shells would be potentially broken since they would be missing any setup process in .zprofile. This is the unfortunate reality, but makes sense in that there is no .xsession or similar, since .zprofile is never run, that can give a users terminals access to initial settings or set things like global environment variables ¹.

This however does not mean that everything should just go in .zprofile, or that the two files are always called together. Since zsh is started in login mode and interactive mode, both .zprofile and .zshrc will run every time a new terminal is created. However, if you run a shell inside of a terminal emulator that will only be an interactive shell and it will lose access to the parent shells settings that were initialized in .zprofile. You can test this by placing an alias in your .zprofile and starting a terminal instance and running that alias, then run zsh and you will find that the alias is no longer available.

Therefore, most shell setup should still go in the .zshrc file so that any shells, terminal or otherwise, are initialized correctly. This is also somewhat in line with how dotfiles on other Linux systems would be written.

Footnotes

1. Why are interactive shells on OSX login shells by default? ↩