Shell initialization files are ways to persist common shell configuration, suchas:

• $PATH and other environment variables
• shell prompt
• shell tab-completion
• aliases, functions
• key bindings

Which initialization files get sourced by the shell is dependent on thecombination of modes in which a particular shell process runs. There are twomain, non-exclusive modes:

• login - e.g. when user logs in to a system with non-graphical interface orvia SSH;
• interactive - shell that has a prompt and whose standard input and errorare both connected to terminals.

These modes can be manually activated with the following flags to bash/zsh:

• -l,--login
• -i

Here are some common operations and shell modes they result in:

• log in to a remote system via SSH:login + interactive
• execute a script remotely, e.g.ssh user@host 'echo $PWD' or withCapistrano:non‑login, non‑interactive
• execute a script remotely and request a terminal, e.g.ssh user@host -t 'echo $PWD':non-login, interactive
• start a new shell process, e.g.bash:non‑login, interactive
• run a script,bash myscript.sh:non‑login, non‑interactive
• run an executable with#!/usr/bin/env bash shebang:non‑login, non‑interactive
• open a new graphical terminal window/tab:
  • on Mac OS X:login, interactive
  • on Linux:non‑login, interactive

In order of activation:

1. login mode:
   1. /etc/profile
   2. ~/.bash_profile,~/.bash_login,~/.profile (only first one that exists)
2. interactivenon-login:
   1. /etc/bash.bashrc (some Linux; not on Mac OS X)
   2. ~/.bashrc
3. non-interactive:
   1. source file in$BASH_ENV

1. /etc/zshenv
2. ~/.zshenv
3. login mode:
   1. /etc/zprofile
   2. ~/.zprofile
4. interactive:
   1. /etc/zshrc
   2. ~/.zshrc
5. login mode:
   1. /etc/zlogin
   2. ~/.zlogin

1. login mode:
   1. /etc/profile
   2. ~/.profile
2. interactive:
   1. source file in$ENV

1. <install-prefix>/config.fish
2. /etc/fish/config.fish
3. ~/.config/fish/config.fish

• Opening a new Terminal window/tab:
  • bash
    • OS X:.bash_profile or.profile (1st found)
    • Linux:.profile (Ubuntu, once per desktop login session) +.bashrc
  • Zsh
    • OS X:.zshenv +.zprofile +.zshrc
    • Linux:.profile (Ubuntu, once per desktop login session) +.zshenv +.zshrc
• Logging into a system via SSH:
  • bash:.bash_profile or.profile (1st found)
  • Zsh:.zshenv +.zprofile +.zshrc
• Executing a command remotely withssh or Capistrano:
  • bash: source file in$BASH_ENV
  • Zsh:.zshenv
• Remote git hook triggered by push over SSH:
  • no init files get sourced, since hooks are runningwithin a restricted shell
  • PATH will be roughly:/usr/libexec/git-core:/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin

• OS X:
  • /etc/paths,/etc/paths.d/*
  • ~/.MacOSX/environment.plist - affectsall graphical programs
  • /etc/launchd.conf
  • TextMate: Preferences -> Advanced -> Shell Variables
• Linux:
  • /etc/environment

This guide was tested with:

• bash 4.2.37, 4.2.39
• Zsh 4.3.11, 5.0

On these operating systems/apps:

• Mac OS X 10.8 (Mountain Lion): Terminal.app, iTerm2
• Ubuntu 12.10: Terminal

See also:

• Environment Variables
• path_helper(8)
• launchd.conf(5)
• pam_env(8)