git.taskfile.build/patterns.md

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Patterns

The task file from the specification is very basic. Commands can also have parameters and call each other.

The following is a collection of more complex task file patterns.

Set default parameter

Fallback to a default value for a parameter.

build() {
    local platform="amd64"
    if [[ -n "$1" ]]; then
        platform="$1"
    fi

Ensure parameter is not empty

Check the first param and exit if it is empty.

deploy() {
    if [[ -z "$1" ]]; then echo "\$1 is empty."; exit; fi

Prompt for input

Use read to ask for inputs.

if [[ -z "$2" ]]; then
	read -p "Enter the task description: " task_description
else
	task_description="$2"
fi

Setup local env vars

Define env vars at the beginning of the task file.

CONFIGURATION_FILE="file.conf"
GIT_BRANCH=$(git symbolic-ref --short -q HEAD)

Template with env vars

Create a parameterized file from a template. Requires envsubst.

template-with-env() {
    echo "Template $CONFIGURATION_FILE"

    export CONFIGURATION_1
    export CONFIGURATION_2=${CONFIGURATION_2:="value"}

    envsubst < "file.conf.template" > "$CONFIGURATION_FILE"
}

Create Python virtual env

Initialize Python virtual env with uv.

init-venv() {
    if [[ ! -d "venv$GIT_BRANCH" ]]; then
        echo "Init venv$GIT_BRANCH with $(uv --version)."
        uv venv "venv$GIT_BRANCH"
    fi
}

Activate Python virtual env

Activate the virtual env.

activate-venv() {
    if [[ -f  ".venv/bin/activate" ]]; then
        source ".venv/bin/activate"
    else
        echo "Could not find .venv/bin/active. Use init-venv to initalize."
    fi
}

Call a Python script

Run a Python script.

generate-password-hash() {
    activate-venv
    if [[ -z "$1" ]]; then echo "\$1 is empty."; exit; fi
    export PASSWORD_PLAIN="$1"
    bin/password-hash
}

The Python script: bin/password-hash

#!/usr/bin/env python3

import os
from passlib.context import CryptContext
crypt_context = CryptContext(schemes=['pbkdf2_sha512', 'plaintext'], deprecated=['plaintext'])

password = os.environ.get('PASSWORD_PLAIN')
print(crypt_context.hash(password))

Command with named parameters

Assuming you have a docker-compose.yml and would like to start selected or all containers.

start() {
    if [[ "$1" =~ "db" ]]; then
        docker compose up -d db
    fi

    if [[ "$1" =~ "admin" ]]; then
        docker compose up -d admin
        echo "Open http://localhost:8000 url in your browser."
    fi

    if [[ "$1" =~ "odoo" ]]; then
        docker compose up -d odoo
        echo "Open http://localhost:8069 url in your browser."
    fi

    if [[ "$1" =~ "mail" ]]; then
	    docker compose up -d mail
        echo "Open http://localhost:8025 url in your browser."
    fi
}

Start all containers with task start and selected with task start db,admin.

Run commands in container

Use docker exec -i to run commands in a container.

drop-db() {
    local database="$1"
    if [[ -z "$database" ]]; then
        database="example"
    fi

    docker exec -i db psql "postgres://odoo:odoo@localhost:5432/postgres" -c "SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname = '$database';"
    docker exec -i db psql "postgres://odoo:odoo@localhost:5432/postgres" -c "DROP DATABASE \"$database\";"
}

Loop over files and folders

Use for to loop over file, folders or arrays.

render() {
    echo "Update index.html for all folders"
    for folder in ./*; do
        if [[ -f "$folder/README.md" ]]; then
            cd "$folder" || exit
            md2html README.md _site/index.html
            cd .. || exit
        fi
    done
}

Parse and convert a file

With this function you can split a file into multiple parts whenever a specific keyword is matching. In this example the keyword is !vault.

convert-vault-file() {
    local file_path="$1"
    local temp_file=$(mktemp)
    local temp_part_file=$(mktemp)
    local write_finished=false
    local current_key=""

    while IFS= read -r line; do
        # Check for keyword
        if [[ "$line" =~ "!vault" ]]; then
            # Process previous vault entry if it exists
            if [[ "$write_finished" = true ]] && [[ -n "$current_key" ]] && [[ -s "$temp_part_file" ]]; then
                # Decrypt part file and write to assemble file
                ansible-vault decrypt "$temp_part_file"
                local value=$(cat "$temp_part_file")
                echo "$current_key: $value" >> "$temp_file"
            fi

            # Set up for new vault entry
            current_key=$(echo "$line" | cut -d':' -f1)
            # Clear the file
            : > "$temp_part_file"
            # Flag as ready to write
            write_finished=true
        else
            if [[ "$write_finished" = true ]]; then
                # Pipe into part file
                echo "$line" >> "$temp_part_file"
            fi
        done
    done < "$file_path"

    # Process the final vault entry
    if [[ "$write_finished" = true ]] && [[ -n "$current_key" ]] && [[ -s "$temp_part_file" ]]; then
        ansible-vault decrypt "$temp_part_file"
        local value=$(cat "$temp_part_file")
        echo "$current_key: $value" >> "$temp_file"
    fi

    # Output assembled file
    cat "$temp_file"
    # Cleanup temp files
    rm -f "$temp_file"
    rm -f "$temp_part_file"
}

Process data

This pattern tries to match the worklow of a jupyter notebook. Create a folder with the data processing scripts:

scripts
├── 01_import-mail-data
├── 02_transform-mail-data
└── 03_export-mail-data

The following function lists the scripts and asks for the number of scripts to run. Every script until the entered number is concatenated and executed.

process-data() {
    while true; do
        local scripts=($(ls scripts))

        echo -e "Available scripts:\n"
        for index in "${!scripts[@]}"; do
            echo "$((index+1)): ${scripts[$index]}"
        done
        echo ""
        read -p "Enter the number of scripts to run (or 'q' to quit): " user_input
        if [[ "$user_input" = "q" ]]; then
            break
        fi

        local temp_file=$(mktemp)
        for index in "${!scripts[@]}"; do
            if (( $user_input >= $((index+1)) )); then
                cat "scripts/${scripts[$index]}" >> "$temp_file"
                echo >> "$temp_file"
            fi
        done

        clear
        echo -e "\nPython Output:\n\n---"
        python "$temp_file"
        local exit_code=$?
        echo -e "---\n"
        echo -e "Exit code: $exit_code\n"
        rm "$temp_file"
    done
}