06 - Loops

Learn how to iterate over lists and files to avoid repetition.

What You'll Learn

• Iterating over lists with with_items
• Iterating over files with with_filetree
• Using loop variables: {{ item }}, {{ index }}, {{ first }}, {{ last }}
• Accessing file properties in loops

Quick Start

cd examples/06-loops

# Run list iteration example
mooncake run --config with-items.yml

# Run file tree iteration example
mooncake run --config with-filetree/config.yml

Examples Included

1. with-items.yml - List Iteration

Iterate over lists of items:

- vars:
    packages:
      - neovim
      - ripgrep
      - fzf

- name: Install package
  shell: brew install {{ item }}
  with_items: "{{ packages }}"

What it does:

• Defines lists in variables
• Installs multiple packages
• Creates directories for multiple users
• Creates user-specific config files

2. with-filetree/ - File Tree Iteration

Iterate over files in a directory:

- name: Copy dotfile
  shell: cp "{{ item.src }}" "/tmp/backup/{{ item.name }}"
  with_filetree: ./files

What it does:

• Iterates over files in ./files/ directory
• Copies dotfiles to backup location
• Filters directories vs files
• Displays file properties

Key Concepts

List Iteration (with_items)

- vars:
    users: [alice, bob, charlie]

- name: Create user directory
  file:
    path: "/home/{{ item }}"
    state: directory
  with_items: "{{ users }}"

This creates:

• /home/alice
• /home/bob
• /home/charlie

File Tree Iteration (with_filetree)

- name: Process file
  shell: echo "Processing {{ item.name }}"
  with_filetree: ./dotfiles
  when: item.is_dir == false

Available properties:

• item.src - Full source path
• item.name - File name
• item.is_dir - Boolean, true if directory

Loop Variables

Both with_items and with_filetree provide additional loop variables:

- vars:
    packages: [git, vim, tmux]

- name: "Installing {{index + 1}}/{{packages|length}}: {{item}}"
  shell: |
    echo "Package: {{item}}"
    echo "Index: {{index}}"
    echo "First: {{first}}"
    echo "Last: {{last}}"
    brew install {{item}}
  with_items: "{{packages}}"

Available loop variables:

• {{ item }} - Current item (for with_items) or file object (for with_filetree)
• {{ index }} - Zero-based iteration index (0, 1, 2, ...)
• {{ first }} - Boolean, true for first iteration
• {{ last }} - Boolean, true for last iteration

Example use cases:

# Progress counter
- name: "[{{index + 1}}/3] Processing {{item}}"
  shell: process {{item}}
  with_items: [a, b, c]

# First-only setup
- name: Initialize on first item
  shell: mkdir -p /tmp/output
  with_items: "{{files}}"
  when: first == true

# Last-only cleanup
- name: Cleanup after last item
  shell: echo "All done!"
  with_items: "{{files}}"
  when: last == true

Filtering in Loops

Skip directories:

- name: Copy files only
  shell: cp "{{ item.src }}" "/tmp/{{ item.name }}"
  with_filetree: ./files
  when: item.is_dir == false

Real-World Use Cases

with_items:

• Installing multiple packages
• Creating multiple users/groups
• Setting up multiple services
• Deploying to multiple servers

with_filetree:

• Managing dotfiles
• Deploying configuration directories
• Backing up files
• Processing file collections

Testing

# List iteration
mooncake run --config with-items.yml

# Check created files
ls -la /tmp/users/

# File tree iteration
mooncake run --config with-filetree/config.yml

# Check backed up files
ls -la /tmp/dotfiles-backup/

Next Steps

Continue to 07-register to learn about capturing command output.