exec zsh vs source zshrc

Two common ways to reload zsh configuration after making changes to ~/.zshrc, but they work fundamentally differently.

source ~/.zshrc

What it does:

• Reloads configuration in the current shell process
• Re-executes all commands in ~/.zshrc within existing environment
• Updates environment variables, aliases, functions

Process behavior:

• Same Process ID (PID)
• Shell history preserved
• Terminal state maintained
• Faster execution

Use when:

• Making small config tweaks during development
• Testing new aliases or environment variables
• You want to keep current terminal state

Example:

bash
# Edit your zshrc
nvim ~/.zshrc

# Reload config
source ~/.zshrc

# Same shell, PID unchanged
echo $$  # Shows same process ID as before

exec zsh

What it does:

• Replaces the current shell process with a completely new one
• Terminates existing shell and starts fresh
• Clears all process state

Process behavior:

• New Process ID (PID) assigned
• Shell history context temporarily lost (until new history loads)
• Complete environment reset
• Prompt fully reinitialized

Use when:

• After major structural changes (new config files, directory reorganization)
• Fixing broken shell state or syntax errors
• source doesn't fully apply changes
• Want guaranteed clean slate

Example:

bash
# Edit your zshrc
nvim ~/.zshrc

# Replace current shell with new process
exec zsh

# New shell, different PID
echo $$  # Shows new process ID

Key Differences

When Each Method Matters

source is sufficient for:

• Adding new aliases
• Changing environment variables
• Updating PATH
• Loading new functions

exec is necessary for:

• Fixing broken completions (syntax errors)
• After restructuring config files
• When source produces errors
• Clearing lingering problematic state

Real-world Example

When transitioning from config/zshrc+/ to shell-config/zsh/:

bash
# Major structural change - use exec
exec zsh

# Verify changes took effect
echo $EDITOR  # Should show 'nvim'

If you had used source, old broken bun completions might have left error state in the environment. exec guarantees a clean start.

Alias Shortcuts

Common aliases for quick reloading:

bash
# In ~/.zshrc or shell-config/zsh/aliases.zsh
alias zshconfig='nvim ~/.zshrc'
alias zshreload='source ~/.zshrc'
alias zshrestart='exec zsh'

Links

Zsh Documentation - Invocation

• URL: https://zsh.sourceforge.io/Doc/Release/Invocation.html↗
• Summary: Official zsh documentation on shell initialization and invocation
• Related: Unix, Shell Configuration