Zsh Hooks

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After exploring “Let Zsh Display Proxy Settings Before Running Network Commands,” I delved deeper into Zsh hooks with ChatGPT. Here’s a concise overview for future reference.

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In Zsh, hooks let you execute custom functions at specific points during shell operations. Beyond preexec, Zsh offers several hooks to enhance your environment:

1. precmd

• When: Before the prompt is displayed.
• Use: Update the prompt or perform cleanup.
• Example:

  precmd() {
    echo "Ready for the next command!"
  }
  

2. chpwd

• When: When the current directory changes.
• Use: Update environment variables or trigger actions based on the directory.
• Example:

  chpwd() {
    echo "Changed to: $PWD"
  }
  

3. preexec_functions & precmd_functions

• When: Similar to preexec and precmd but support multiple functions.
• Use: Attach multiple actions without overriding existing hooks.
• Example:

  precmd_functions+=(additional_precmd)
    
  additional_precmd() {
    echo "Additional precmd task."
  }
  

4. TRAPDEBUG

• When: After each command, before results display.
• Use: Debugging, logging commands.
• Example:

  TRAPDEBUG() {
    echo "Executed: $1"
  }
  

5. TRAPEXIT

• When: When the shell exits.
• Use: Cleanup tasks or display exit messages.
• Example:

  TRAPEXIT() {
    echo "Goodbye!"
  }
  

6. zle Hooks

• When: During line editing.
• Use: Customize command line behavior.
• Example:

  zle-line-init() {
    echo "Editing a new command."
  }
  zle -N zle-line-init
  

7. History Hooks (zshaddhistory, zshremovehistory)

• When: Adding or removing history entries.
• Use: Filter or manage history.
• Example:

  zshaddhistory() {
    [[ $1 == *"secret"* ]] && return 1
    return 0
  }
  

8. periodic

• When: At intervals set by period.
• Use: Routine checks or updates.
• Example:

  periodic() {
    echo "Running periodic task..."
  }
  

9. add-zsh-hook

• Purpose: Safely add functions to hooks.
• Use: Append multiple functions without overwriting.
• Example:

  add-zsh-hook precmd another_precmd
    
  another_precmd() {
    echo "Another precmd function."
  }
  

Summary

Zsh’s hook system is versatile, enabling automation and customization:

• preexec: Before command execution.
• precmd: Before prompt display.
• chpwd: On directory change.
• TRAPDEBUG: Post-command for debugging.
• TRAPEXIT: On shell exit.
• zle Hooks: During line editing.
• History Hooks: Managing command history.
• periodic: At set intervals.
• add-zsh-hook: Adding multiple hook functions.

Utilizing these hooks can greatly enhance your Zsh experience, making your shell more efficient and tailored to your workflow.

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