⇦ Back

When you open up a terminal there are a number of commands that get run in the background before you even do anything. These commands are contained in ‘startup files’ and can often be edited in order to change the default behaviour of your terminal.

Bash

Bash is the default shell and language for most Linux terminals. It is also installed on macOS but is no longer the default.

When you open a Bash shell the following startup files might get run (depending on which mode(s) the terminal is opened in and also on if the files exist - not all of them have to) in the following order:

  1. Profile files (for login shells, regardless of whether they are interactive or not):
    1. /etc/profile (this calls path_helper which initialises the PATH variable)
    2. ~/.bash_profile, ~/.bash_login or ~/.profile (only the first one that exists)
  2. Run command files (only for interactive, non-login shells - which is the default for Ubuntu - or remote shells):
    1. /etc/bash.bashrc (only for some Linux distros, and not on macOS)
    2. ~/.bashrc
  3. For non-interactive shells, whether login or not:
    1. The BASH_ENV variable gets sourced

Additionally, two files are run at the end of a login shell’s session:

  1. Logout files:
    1. ~/.bash_logout
    2. /etc/bash_logout

Opening Terminal on Ubuntu will create a Bash shell in interactive but not in login mode. This means that /etc/bash.bashrc and ~/.bashrc get sourced (the code they contain gets run).

Check the Mode

Here’s how to check which modes you are in:

  • Check if you are in an interactive shell:

    [[ $- == *i* ]] && echo 'Interactive' || echo 'Not interactive'

  • Check if you are in a login shell:

    shopt -q login_shell && echo 'Login shell' || echo 'Not login shell'

Z Shell

Z Shell (zsh) is the default shell and language for macOS terminals. By default, opening Terminal on macOS will create a shell in both interactive and login modes although sub-shells (created by, for example, running zsh in a terminal) will only be interactive, not login.

When you open a shell the following startup files might get run (depending on which mode(s) the terminal is opened in and also on if the files exist - not all of them have to) in the following order:

  1. Environment files (for all shells):
    1. /etc/zshenv
    2. ~/.zshenv
  2. Profile files (only for login shells):
    1. /etc/zprofile. This calls path_helper which reads the paths contained in the following files in order, concatenates them and prepends them to PATH (note that if the PATH variable is already set it will not add duplicate paths to it but it could have the effect of re-ordering it):
      1. /etc/paths
      2. Files in /etc/paths.d
    2. ~/.zprofile
  3. Run command files (only for interactive shells):
    1. /etc/zshrc
    2. ~/.zshrc
  4. Login files (again, only for login shells):
    1. /etc/zlogin
    2. ~/.zlogin

Additionally, two files are run at the end of a login shell’s session:

  1. Logout files:
    1. ~/.zlogout
    2. /etc/zlogout

Check the Mode

Remember that a shell can be both interactive and login, or it could be interactive but non-login or it could be neither. It’s rare (but not impossible) to get a non-interactive login shell. Here’s how to check:

  • Check if you are in an interactive shell:

    [[ -o interactive ]] && echo "Interactive" || echo "Non-Interactive"

  • Check if you are in a login shell:

    [[ -o login ]] && echo "Login" || echo "Non-Login"