Shell startup order, env vars, PATH, XDG, locale, chsh.

Bash startup order

Login shell (ssh, tty, bash --login):
  /etc/profile
    → /etc/profile.d/*.sh
  ~/.bash_profile (or ~/.bash_login, or ~/.profile — first found)
    → usually sources ~/.bashrc

Interactive non-login (terminal emulator):
  /etc/bash.bashrc
  ~/.bashrc

Non-interactive (script):
  $BASH_ENV (if set)

Zsh startup order

Always (every zsh, incl. scripts):
  /etc/zshenv ; ~/.zshenv

Login:
  /etc/zprofile ; ~/.zprofile

Interactive:
  /etc/zshrc ; ~/.zshrc

After zshrc on login:
  /etc/zlogin ; ~/.zlogin

On logout:
  ~/.zlogout ; /etc/zlogout

Quick reference

Where to put env vars:

• Bash: ~/.bash_profile (login) or ~/.bashrc (if profile sources it).
• Zsh: ~/.zshenv (everywhere) or ~/.zprofile (login).
• Both shells: ~/.profile and source from both. Or ~/.config/environment.d/ for systemd user sessions.

Environment variables

• View all: env / printenv

• One variable: echo $HOME / printenv PATH

• Set + export: export MY_VAR="value"

• Single-command only: MY_VAR=value command

• Unset: unset MY_VAR

• Persist (example): echo 'export MY_VAR="value"' >> ~/.bashrc

Common variables

System-wide

• /etc/environment — simple KEY=VALUE (no expansion, no export):

  EDITOR=vim
  PATH="/usr/local/bin:/usr/bin:/bin"
  

• /etc/profile.d/custom.sh — shell scripts at login:

  export GOPATH="$HOME/go"
  export PATH="$PATH:$GOPATH/bin"
  

systemd user environment

~/.config/environment.d/50-custom.conf:

EDITOR=vim
PATH=${HOME}/.local/bin:${PATH}

• Show / set / import:

  systemctl --user show-environment
  systemctl --user set-environment MY_VAR=value
  systemctl --user import-environment
  

PATH

• View one per line: echo $PATH | tr ':' '\n'

• Prepend (higher priority): export PATH="$HOME/.local/bin:$PATH"

• Append: export PATH="$PATH:/opt/custom/bin"

• Conditional (avoid dupes): [[ ":$PATH:" != *":$HOME/.local/bin:"* ]] && export PATH="$HOME/.local/bin:$PATH"

• Resolve which binary: which python / type python / command -v python

• Show all matches: which -a python / type -a python

XDG base directories

• Defaults:

  export XDG_CONFIG_HOME="$HOME/.config"
  export XDG_DATA_HOME="$HOME/.local/share"
  export XDG_STATE_HOME="$HOME/.local/state"
  export XDG_CACHE_HOME="$HOME/.cache"
  # XDG_RUNTIME_DIR set by systemd (typically /run/user/$UID)
  

• Create dirs: mkdir -p ~/.config ~/.local/share ~/.local/state ~/.cache ~/.local/bin

Minimal bash config

~/.bash_profile:

export EDITOR=vim
export VISUAL=vim
export PAGER=less
export PATH="$HOME/.local/bin:$PATH"
[[ -f ~/.bashrc ]] && source ~/.bashrc

~/.bashrc:

[[ $- != *i* ]] && return

export HISTSIZE=10000
export HISTFILESIZE=20000
export HISTCONTROL=ignoreboth
shopt -s histappend globstar checkwinsize cdspell dirspell

alias ls='ls --color=auto'
alias ll='ls -lah'
alias grep='grep --color=auto'
alias ..='cd ..'

PS1='\[\e[32m\]\u@\h\[\e[0m\]:\[\e[34m\]\w\[\e[0m\]\$ '

[[ -f /usr/share/bash-completion/bash_completion ]] && source /usr/share/bash-completion/bash_completion

Minimal zsh config

~/.zshenv:

export EDITOR=vim
export VISUAL=vim
export PAGER=less
export PATH="$HOME/.local/bin:$PATH"

~/.zshrc:

HISTSIZE=10000
SAVEHIST=20000
HISTFILE=~/.zsh_history
setopt HIST_IGNORE_DUPS HIST_IGNORE_SPACE SHARE_HISTORY APPEND_HISTORY
setopt AUTO_CD CORRECT GLOB_DOTS EXTENDED_GLOB

alias ls='ls --color=auto'
alias ll='ls -lah'
alias grep='grep --color=auto'
alias ..='cd ..'

bindkey -e
autoload -Uz compinit && compinit
zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}'
zstyle ':completion:*' menu select

autoload -Uz promptinit && promptinit
PROMPT='%F{green}%n@%m%f:%F{blue}%~%f%# '

Change default shell

• List allowed: cat /etc/shells

• Change own: chsh -s /bin/zsh

• Change other (root): sudo chsh -s /bin/zsh otheruser

• Install zsh: sudo pacman -S zsh zsh-completions

• Verify: echo $SHELL

Locale

• Show / list: locale / locale -a

• Generate (after editing /etc/locale.gen): sudo locale-gen

• Set system locale + keymap: sudo localectl set-locale LANG=en_US.UTF-8 sudo localectl set-keymap us

• Status: localectl status

• Per-session overrides:

  export LANG=en_US.UTF-8
  export LC_ALL=en_US.UTF-8
  export LC_TIME=en_GB.UTF-8       # 24-hour, DD/MM/YYYY
  export LC_NUMERIC=en_US.UTF-8    # 1,000.00
  export LC_COLLATE=C              # sort by byte value