Dotfiles

Dotfiles are configuration files that start with a dot (.), making them hidden by default. Understanding which files are loaded when is crucial for proper shell configuration.

Key Files

File	Purpose	When Loaded
.bash_profile	Login shell config	SSH, new terminal (macOS)
.bashrc	Interactive shell config	New bash instance
.profile	Generic login config	Login shells (sh compatible)
.bash_logout	Cleanup commands	Logout from login shell

Login vs Non-Login Shells

Login Shell

A login shell is started when you:

• Log in via SSH
• Log in at a console
• Open Terminal.app on macOS (by default)
• Run bash --login or bash -l

Login shells read:

1. /etc/profile
2. First of: ~/.bash_profile, ~/.bash_login, or ~/.profile

Non-Login (Interactive) Shell

A non-login interactive shell is started when you:

• Open a new tab in most Linux terminals
• Run bash from another shell
• Open a subshell

Non-login shells read:

1. /etc/bash.bashrc (Linux) or /etc/bashrc (some systems)
2. ~/.bashrc

Visual Summary

┌─────────────────────────────────────────────────┐
│                   Login Shell                    │
│  ┌─────────────────────────────────────────┐    │
│  │  /etc/profile                            │    │
│  │  ~/.bash_profile OR ~/.profile           │    │
│  │       │                                  │    │
│  │       └── sources ~/.bashrc (recommended)│    │
│  └─────────────────────────────────────────┘    │
└─────────────────────────────────────────────────┘

┌─────────────────────────────────────────────────┐
│              Non-Login Interactive              │
│  ┌─────────────────────────────────────────┐    │
│  │  ~/.bashrc                               │    │
│  └─────────────────────────────────────────┘    │
└─────────────────────────────────────────────────┘

Recommended Structure

~/.bash_profile

Keep this minimal - just source .bashrc:

# ~/.bash_profile

# Load .bashrc if it exists
if [[ -f ~/.bashrc ]]; then
    source ~/.bashrc
fi

# Login-specific settings (rare)
# Example: start ssh-agent once at login

~/.bashrc

Main configuration file:

# ~/.bashrc

# Exit if not interactive
[[ $- != *i* ]] && return

# ──────────────────────────────────────────────
# Shell Options
# ──────────────────────────────────────────────

shopt -s histappend     # Append to history
shopt -s checkwinsize   # Update LINES/COLUMNS
shopt -s globstar       # ** for recursive glob (bash 4+)
shopt -s cdspell        # Autocorrect cd typos

# ──────────────────────────────────────────────
# History
# ──────────────────────────────────────────────

HISTSIZE=10000
HISTFILESIZE=20000
HISTCONTROL=ignoreboth:erasedups

# ──────────────────────────────────────────────
# Environment
# ──────────────────────────────────────────────

export EDITOR=vim
export VISUAL=vim
export PAGER=less

# ──────────────────────────────────────────────
# Path
# ──────────────────────────────────────────────

export PATH="$HOME/.local/bin:$PATH"

# ──────────────────────────────────────────────
# Source additional files
# ──────────────────────────────────────────────

for file in ~/.bash_{aliases,functions,prompt}; do
    [[ -r "$file" ]] && source "$file"
done
unset file

Modular Configuration

Split configuration into logical files:

~/.bashrc              # Main config, sources others
~/.bash_aliases        # All aliases
~/.bash_functions      # All functions
~/.bash_prompt         # Prompt configuration
~/.bash_local          # Machine-specific (not in git)

~/.bash_aliases

# ~/.bash_aliases

# Navigation
alias ..='cd ..'
alias ...='cd ../..'
alias ~='cd ~'

# Listing
alias ls='ls --color=auto'
alias ll='ls -lah'
alias la='ls -A'

# Safety
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

# Git
alias g='git'
alias gs='git status'
alias gc='git commit'

~/.bash_functions

# ~/.bash_functions

# Create directory and cd into it
mkcd() {
    mkdir -p "$1" && cd "$1"
}

# Extract any archive
extract() {
    if [[ -f "$1" ]]; then
        case "$1" in
            *.tar.bz2) tar xjf "$1" ;;
            *.tar.gz)  tar xzf "$1" ;;
            *.tar.xz)  tar xJf "$1" ;;
            *.bz2)     bunzip2 "$1" ;;
            *.gz)      gunzip "$1" ;;
            *.tar)     tar xf "$1" ;;
            *.tbz2)    tar xjf "$1" ;;
            *.tgz)     tar xzf "$1" ;;
            *.zip)     unzip "$1" ;;
            *.Z)       uncompress "$1" ;;
            *)         echo "Unknown format: $1" ;;
        esac
    else
        echo "Not a file: $1"
    fi
}

~/.bash_local

Machine-specific configuration (don't commit to git):

# ~/.bash_local

# Work-specific paths
export PATH="/opt/company-tools/bin:$PATH"

# API keys (better: use a secrets manager)
export API_KEY="xxx"

Source it at the end of .bashrc:

[[ -f ~/.bash_local ]] && source ~/.bash_local

Checking Shell Type

In scripts, detect shell type:

# Is this a login shell?
shopt -q login_shell && echo "Login" || echo "Non-login"

# Is this interactive?
[[ $- == *i* ]] && echo "Interactive" || echo "Non-interactive"

System-Wide Configuration

File	Purpose
/etc/profile	System-wide login shell config
/etc/bash.bashrc	System-wide interactive shell config
/etc/bashrc	Alternative location (RHEL/CentOS)
/etc/profile.d/*.sh	Modular system-wide scripts

These are read before user dotfiles.

Platform Differences

macOS

• Terminal.app opens login shells by default
• System uses zsh as default (since Catalina)
• Bash 3.2 included; Bash 5.x via Homebrew

Configure Terminal.app for non-login shells:

Preferences > General > Shells open with: Command /bin/bash

Linux

• Most terminals open non-login interactive shells
• Login via console or SSH opens login shell
• Usually has Bash 5.x

Windows (WSL/Git Bash)

• Similar to Linux behavior
• May have additional files like .bash_profile.local

Debugging Configuration

See What's Being Read

Add to top of each file:

echo "Loading ~/.bashrc"

Trace Execution

bash -x          # Start with tracing

Or within a session:

set -x           # Enable tracing
# do things
set +x           # Disable tracing

Start Fresh

env -i bash --noprofile --norc

Common Problems

Changes Don't Take Effect

After editing, reload:

source ~/.bashrc
# or
. ~/.bashrc

PATH Gets Longer Each Time

Add PATH entries only once:

[[ ":$PATH:" != *":/new/path:"* ]] && export PATH="/new/path:$PATH"

Bashrc Loaded Twice

Check for multiple source calls in .bash_profile.

Interactive Check Missing

Non-interactive scripts might source .bashrc. Guard with:

# At top of .bashrc
[[ $- != *i* ]] && return

Version Control

Keep dotfiles in git:

# Initialize dotfiles repo
cd ~
git init --bare ~/.dotfiles

# Alias for managing
alias dotfiles='git --git-dir=$HOME/.dotfiles --work-tree=$HOME'

# Add files
dotfiles add .bashrc
dotfiles commit -m "Add bashrc"

Or use a tool like chezmoi or yadm.

Try It

1. Check current shell type:

   shopt -q login_shell && echo "Login" || echo "Non-login"
   [[ $- == *i* ]] && echo "Interactive"
   

2. Create modular structure:

   # Create separate alias file
   echo 'alias hello="echo Hello from bash_aliases"' > ~/.bash_aliases
   
   # Source it from .bashrc
   echo '[[ -f ~/.bash_aliases ]] && source ~/.bash_aliases' >> ~/.bashrc
   
   # Reload and test
   source ~/.bashrc
   hello
   

3. Test login vs non-login:

   # Start login shell
   bash --login
   exit
   
   # Start non-login shell
   bash
   exit
   

Summary

• Use .bash_profile for login shells, have it source .bashrc
• Put all interactive configuration in .bashrc
• Split configuration into modular files
• Use .bash_local for machine-specific settings
• Guard .bashrc with interactive check
• Version control your dotfiles