The cull-gmail provides a software library and command line program to enable the culling of emails using the Gmail API.

Quick Start

Get started with cull-gmail in minutes using the built-in setup command:

1. Get OAuth2 credentials from Google Cloud Console
2. Initialize cull-gmail with guided setup:

   # Interactive setup (recommended)
   cull-gmail init --interactive --credential-file ~/Downloads/client_secret.json
   
   # Or preview first
   cull-gmail init --dry-run
   

3. Verify your setup:

   cull-gmail labels
   

Main Features

• Easy initialization: Guided setup with OAuth2 credential validation and secure file handling
• Flexible configuration: Support for file-based config, environment variables, and ephemeral tokens
• Safety first: Dry-run mode by default, interactive confirmations, and timestamped backups
• Label management: List and inspect Gmail labels for rule planning
• Message operations: Query, filter, and perform batch operations on Gmail messages
• Rule-based automation: Configure retention rules with time-based filtering and automated actions
• Token portability: Export/import OAuth2 tokens for containerized and CI/CD environments

Running the optional Gmail integration test

An optional, ignored integration test exercises the Gmail API end-to-end (networked). It is ignored by default and will not run in CI.

Steps to run locally:

1. Ensure you have valid OAuth client credentials configured for the library (see ClientConfig::builder() usage in docs).
2. Run the test explicitly with the ignored flag:

cargo test --test gmail_message_list_integration -- --ignored

Notes:

• The test performs a lightweight listing (max 10 messages) and should be safe, but it still uses your Gmail account.
• Do not run this in CI; it is intended only for local verification.

cull-gmail CLI Documentation

A command-line program for managing Gmail messages using the Gmail API. The tool provides subcommands for label querying, message querying, rule configuration, and rule execution to trash/delete messages with built-in safety features like dry-run mode.

Installation

From Crates.io

cargo install cull-gmail

From Source

git clone https://github.com/jerus-org/cull-gmail.git
cd cull-gmail
cargo install --path .

Verify Installation

cull-gmail --version

Authentication Setup

1. Google Cloud Console Setup

1. Visit the Google Cloud Console
2. Create a new project or select an existing one
3. Enable the Gmail API:
   • Go to "APIs & Services" > "Library"
   • Search for "Gmail API" and enable it
4. Create OAuth2 credentials:
   • Go to "APIs & Services" > "Credentials"
   • Click "Create Credentials" > "OAuth client ID"
   • Choose "Desktop application"
   • Download the JSON file

2. Configure cull-gmail

1. Create the configuration directory:

   mkdir -p ~/.cull-gmail
   

2. Copy your OAuth2 credential file:

   cp ~/Downloads/client_secret_*.json ~/.cull-gmail/client_secret.json
   

3. Create configuration file ~/.cull-gmail/cull-gmail.toml:

   credential_file = "client_secret.json"
   config_root = "~/.cull-gmail"
   rules = "rules.toml"
   execute = false  # Start in dry-run mode
   

3. First Run Authentication

Run any command to trigger the OAuth flow:

cull-gmail labels

This will:

1. Open your browser for Google authentication
2. Prompt you to grant Gmail access
3. Save tokens to ~/.cull-gmail/gmail1/

Configuration

Configuration File

Location: ~/.cull-gmail/cull-gmail.toml

# OAuth2 credential file (relative to config_root)
credential_file = "client_secret.json"

# Configuration directory
config_root = "~/.cull-gmail"

# Rules file
rules = "rules.toml"

# Default execution mode (false = dry-run, true = execute)
execute = false

# Alternative: Direct OAuth2 configuration
# client_id = "your-client-id.apps.googleusercontent.com"
# client_secret = "your-client-secret"
# token_uri = "https://oauth2.googleapis.com/token"
# auth_uri = "https://accounts.google.com/o/oauth2/auth"

Environment Variables

Override any configuration setting:

export APP_CREDENTIAL_FILE="client_secret.json"
export APP_EXECUTE="true"
export APP_CLIENT_ID="your-client-id"
export APP_CLIENT_SECRET="your-client-secret"
export APP_CONFIG_ROOT="/custom/config/path"

Command Structure

cull-gmail [OPTIONS] [COMMAND]

Global Options

• -v, --verbose...: Increase logging verbosity (can be used multiple times)
• -q, --quiet...: Decrease logging verbosity
• -h, --help: Show help
• -V, --version: Show version

Commands

• labels: List available Gmail labels
• messages: Query and operate on messages
• rules: Configure and run retention rules

Command Reference

Labels Command

List all labels in your Gmail account:

cull-gmail labels

Example Output:

INBOX: INBOX
IMPORTANT: IMPORTANT
CHAT: CHAT
SENT: SENT
DRAFT: DRAFT
promotions: Label_1234567890
old-emails: Label_0987654321

Messages Command

Query and operate on Gmail messages.

Syntax

cull-gmail messages [OPTIONS] <ACTION>

Options

• -l, --labels <LABELS>: Filter by labels (can be used multiple times)
• -m, --max-results <MAX_RESULTS>: Maximum results per page [default: 200]
• -p, --pages <PAGES>: Maximum number of pages (0=all) [default: 1]
• -Q, --query <QUERY>: Gmail query string

Actions

• list: Display message information
• trash: Move messages to trash
• delete: Permanently delete messages

Examples

List recent messages:

cull-gmail messages -m 10 list

List promotional emails older than 6 months:

cull-gmail messages -Q "label:promotions older_than:6m" list

Move old promotional emails to trash:

cull-gmail messages -Q "label:promotions older_than:1y" trash

Permanently delete very old messages:

cull-gmail messages -Q "older_than:5y -label:important" delete

Query with multiple labels:

cull-gmail messages -l "promotions" -l "newsletters" -Q "older_than:3m" list

Process all pages (not just first page):

cull-gmail messages -p 0 -Q "older_than:2y" list

Rules Command

Manage retention rules for automated email lifecycle management.

Syntax

cull-gmail rules <SUBCOMMAND>

Subcommands

• config: Configure retention rules
• run: Execute configured rules

Rules Config Command

Configure retention rules:

cull-gmail rules config <ACTION>

Config Actions

• rules: Manage rule definitions
• label: Add/remove labels from rules
• action: Set action (trash/delete) on rules

Example Rules Configuration:

Create/edit ~/.cull-gmail/rules.toml:

[rules."1"]
id = 1
retention = { age = "y:1", generate_label = true }
labels = ["old-emails"]
action = "Trash"

[rules."2"]
id = 2
retention = { age = "m:6", generate_label = true }
labels = ["promotions", "newsletters"]
action = "Trash"

[rules."3"]
id = 3
retention = { age = "y:5", generate_label = true }
labels = ["archive"]
action = "Delete"

Rules Run Command

Execute configured rules:

cull-gmail rules run [OPTIONS]

Options

• -e, --execute: Actually perform actions (without this, runs in dry-run mode)
• -t, --skip-trash: Skip rules with "trash" action
• -d, --skip-delete: Skip rules with "delete" action

Examples

Dry-run all rules (safe, no changes made):

cull-gmail rules run

Execute all rules:

cull-gmail rules run --execute

Execute only delete rules:

cull-gmail rules run --execute --skip-trash

Execute only trash rules:

cull-gmail rules run --execute --skip-delete

Gmail Query Syntax

The -Q, --query option supports Gmail's powerful search syntax:

Date Queries

# Relative dates
-Q "older_than:1y"        # Older than 1 year
-Q "newer_than:30d"       # Newer than 30 days
-Q "older_than:6m"        # Older than 6 months

# Absolute dates
-Q "after:2023/1/1"       # After January 1, 2023
-Q "before:2023/12/31"    # Before December 31, 2023

Label Queries

# Has label
-Q "label:promotions"
-Q "label:important"

# Does NOT have label (note the minus sign)
-Q "-label:important"
-Q "-label:spam"

Content Queries

# Subject line
-Q "subject:newsletter"
-Q "subject:(unsubscribe OR newsletter)"

# From/To
-Q "from:noreply@example.com"
-Q "to:me@example.com"

# Message content
-Q "unsubscribe"
-Q "has:attachment"

Status Queries

# Read status
-Q "is:unread"
-Q "is:read"

# Star status
-Q "is:starred"
-Q "-is:starred"

# Size
-Q "size:larger_than:10M"
-Q "size:smaller_than:1M"

Combined Queries

# Complex combinations
-Q "label:promotions older_than:6m -is:starred"
-Q "from:newsletters@example.com older_than:1y has:attachment"
-Q "subject:newsletter OR subject:promo older_than:3m"

Common Workflows

1. Clean Up Promotional Emails

# Step 1: Preview what will be affected
cull-gmail messages -Q "label:promotions older_than:6m" list

# Step 2: Move to trash (can be recovered for 30 days)
cull-gmail messages -Q "label:promotions older_than:6m" trash

2. Archive Old Conversations

# Archive conversations older than 2 years (excluding starred)
cull-gmail messages -Q "older_than:2y -is:starred -label:important" trash

3. Delete Very Old Messages

# Permanently delete messages older than 5 years (be careful!)
cull-gmail messages -Q "older_than:5y -is:starred -label:important" delete

4. Rule-Based Automation

# Set up rules in ~/.cull-gmail/rules.toml, then:

# Preview what rules will do
cull-gmail rules run

# Execute rules
cull-gmail rules run --execute

5. Scheduled Cleanup

Add to your crontab for weekly cleanup:

# Edit crontab
crontab -e

# Add this line (runs every Sunday at 2 AM)
0 2 * * 0 /home/user/.cargo/bin/cull-gmail rules run --execute >> /var/log/cull-gmail.log 2>&1

Safety Features

Dry-Run Mode

• Default behaviour: All operations are dry-run unless explicitly executed
• Messages: Use list action to preview what would be affected
• Rules: Run without --execute flag to see what would happen

Confirmation and Logging

• All operations are logged with detailed information
• Use -v for verbose logging to see exactly what's happening
• Check log output before running destructive operations

Recoverable Operations

• Trash: Messages moved to trash can be recovered for 30 days
• Delete: Permanent deletion - cannot be undone

Logging and Debugging

Environment Variables

# Set log level
export RUST_LOG=cull_gmail=debug

# Enable all logging
export RUST_LOG=debug

Verbosity Levels

# Quiet (errors only)
cull-gmail -q messages list

# Normal (default)
cull-gmail messages list

# Verbose (info level)
cull-gmail -v messages list

# Very verbose (debug level)
cull-gmail -vv messages list

# Maximum verbosity (trace level)
cull-gmail -vvv messages list

Log Information

• Error: Critical issues
• Warn: Non-fatal issues, dry-run notifications
• Info: General operation info, message subjects, counts
• Debug: Detailed API calls, query strings
• Trace: Very detailed debugging information

Troubleshooting

Authentication Issues

Problem: "Authentication failed" or "Invalid credentials"

Solutions:

1. Verify OAuth2 credential file exists and is valid JSON
2. Check OAuth client is configured as "Desktop Application"
3. Clear token cache: rm -rf ~/.cull-gmail/gmail1
4. Re-run authentication: cull-gmail labels

Problem: "Access denied" or "Insufficient permissions"

Solutions:

1. Verify Gmail API is enabled in Google Cloud Console
2. Check OAuth scopes include Gmail access
3. Re-authenticate with proper permissions

Query Issues

Problem: "No messages found" when you expect results

Solutions:

1. Test query in Gmail web interface first
2. Check label names: cull-gmail labels
3. Verify query syntax (no typos)
4. Use -v flag to see the actual query being sent

Problem: Query returns unexpected results

Solutions:

1. Use messages list to preview before trash/delete
2. Check for operator precedence in complex queries
3. Test simpler queries first, then combine

Performance Issues

Problem: Operations are slow or timeout

Solutions:

1. Reduce page size: -m 100
2. Limit pages: -p 5 instead of -p 0
3. Use more specific queries to reduce result sets
4. Check Gmail API quotas in Google Cloud Console

Configuration Issues

Problem: "Configuration not found" or "Config parse error"

Solutions:

1. Verify config file path: ~/.cull-gmail/cull-gmail.toml
2. Check TOML syntax
3. Ensure OAuth2 credential file path is correct
4. Use absolute paths if relative paths fail

Exit Codes

• 0: Success
• 101: Error (check stderr for details)

Examples

Basic Message Management

# List all labels
cull-gmail labels

# List first 50 messages
cull-gmail messages -m 50 list

# List promotional emails from last year
cull-gmail messages -Q "label:promotions after:2023/1/1" list

Batch Operations

# Move old promotional emails to trash
cull-gmail messages -Q "label:promotions older_than:1y" trash

# Permanently delete very old messages (careful!)
cull-gmail messages -Q "older_than:5y -is:starred" delete

Rule-Based Management

# Preview all rules
cull-gmail rules run

# Execute only trash rules
cull-gmail rules run --execute --skip-delete

# Execute all rules
cull-gmail rules run --execute

See Also

• Library Documentation - Rust API reference and programming examples
• API Documentation - Generated API reference
• Repository - Source code, examples, and issue tracking
• Gmail API Documentation - Google's official API docs
• Gmail Search Operators - Complete Gmail query syntax

cull-gmail Library Documentation

The cull-gmail library provides a Rust API for managing Gmail messages through the Gmail API. It enables programmatic email culling operations including authentication, message querying, filtering, and batch operations (trash/delete).

Installation

Add the library to your Cargo.toml:

[dependencies]
cull-gmail = "0.0.16"
tokio = { version = "1.0", features = ["macros", "rt-multi-thread"] }

Quick Start

Here's a minimal example to get started:

use cull_gmail::{ClientConfig, GmailClient, Result};

#[tokio::main]
async fn main() -> Result<()> {
    // Load configuration from file or environment
    let config = ClientConfig::builder()
        .with_credential_file("credential.json")
        .build();
    
    // Create Gmail client and authenticate
    let mut client = GmailClient::new_with_config(config).await?;
    
    // List first 10 messages
    client.set_max_results(10);
    client.get_messages(1).await?;
    client.log_messages().await?;
    
    Ok(())
}

Core Types

GmailClient

The main client for interacting with Gmail API:

use cull_gmail::{GmailClient, MessageList};

// Create client with configuration
let mut client = GmailClient::new_with_config(config).await?;

// Query messages with Gmail search syntax
client.set_query("older_than:1y label:promotions");
client.add_labels(&["INBOX".to_string()])?;
client.set_max_results(200);

// Get messages (0 = all pages, 1 = first page only)
client.get_messages(0).await?;

// Access message data
let messages = client.messages();
let message_ids = client.message_ids();

ClientConfig

Handles authentication and configuration:

use cull_gmail::ClientConfig;

// From credential file
let config = ClientConfig::builder()
    .with_credential_file("path/to/credential.json")
    .with_config_path(".cull-gmail")
    .build();

// From individual OAuth2 parameters
let config = ClientConfig::builder()
    .with_client_id("your-client-id")
    .with_client_secret("your-client-secret")
    .with_auth_uri("https://accounts.google.com/o/oauth2/auth")
    .with_token_uri("https://oauth2.googleapis.com/token")
    .add_redirect_uri("http://localhost:8080")
    .build();

Rules and Retention Policies

Define automated message lifecycle rules:

use cull_gmail::{Rules, Retention, MessageAge, EolAction};

// Create a rule set
let mut rules = Rules::new();

// Add retention rules
rules.add_rule(
    Retention::new(MessageAge::Years(1), true),
    Some(&"old-emails".to_string()),
    false // false = trash, true = delete
);

rules.add_rule(
    Retention::new(MessageAge::Months(6), true),
    Some(&"promotions".to_string()),
    false
);

// Save rules to file
rules.save()?;

// Load existing rules
let loaded_rules = Rules::load()?;

Message Operations

Batch operations on messages:

use cull_gmail::{RuleProcessor, EolAction};

// Set up rule and dry-run mode
client.set_execute(false); // Dry run - no actual changes
let rule = rules.get_rule(1).unwrap();
client.set_rule(rule);

// Find messages matching rule for a label
client.find_rule_and_messages_for_label("promotions").await?;

// Check what action would be performed
if let Some(action) = client.action() {
    match action {
        EolAction::Trash => println!("Would move {} messages to trash", client.messages().len()),
        EolAction::Delete => println!("Would delete {} messages permanently", client.messages().len()),
    }
}

// Execute for real
client.set_execute(true);
match client.action() {
    Some(EolAction::Trash) => client.batch_trash().await?,
    Some(EolAction::Delete) => client.batch_delete().await?,
    None => println!("No action specified"),
}

Configuration

OAuth2 Setup

1. Create OAuth2 credentials in Google Cloud Console
2. Download the credential JSON file
3. Configure the client:

let config = ClientConfig::builder()
    .with_credential_file("path/to/credential.json")
    .build();

Configuration File

The library supports TOML configuration files (default: ~/.cull-gmail/cull-gmail.toml):

credentials = "credential.json"
config_root = "~/.cull-gmail"
rules = "rules.toml"
execute = false

# Alternative: direct OAuth2 parameters
# client_id = "your-client-id"
# client_secret = "your-client-secret"
# token_uri = "https://oauth2.googleapis.com/token"
# auth_uri = "https://accounts.google.com/o/oauth2/auth"

Environment Variables

Override configuration with environment variables:

export APP_CREDENTIALS="/path/to/credential.json"
export APP_EXECUTE="true"
export APP_CLIENT_ID="your-client-id"
export APP_CLIENT_SECRET="your-client-secret"

Error Handling

The library uses a comprehensive error type:

use cull_gmail::{Error, Result};

match client.get_messages(1).await {
    Ok(_) => println!("Success!"),
    Err(Error::NoLabelsFound) => println!("No labels found in mailbox"),
    Err(Error::LabelNotFoundInMailbox(label)) => println!("Label '{}' not found", label),
    Err(Error::GoogleGmail1(e)) => println!("Gmail API error: {}", e),
    Err(e) => println!("Other error: {}", e),
}

Common error types:

• NoLabelsFound: Mailbox has no labels
• LabelNotFoundInMailbox(String): Specific label not found
• RuleNotFound(usize): Rule ID doesn't exist
• GoogleGmail1(Box<google_gmail1::Error>): Gmail API errors
• StdIO(std::io::Error): File I/O errors
• Config(config::ConfigError): Configuration errors

Async Runtime

The library requires an async runtime (Tokio recommended):

[dependencies]
tokio = { version = "1.0", features = ["macros", "rt-multi-thread"] }

#[tokio::main]
async fn main() -> cull_gmail::Result<()> {
    // Your code here
    Ok(())
}

Gmail Query Syntax

The library supports Gmail's search syntax for message queries:

// Date-based queries
client.set_query("older_than:1y");           // Older than 1 year
client.set_query("newer_than:30d");          // Newer than 30 days
client.set_query("after:2023/1/1");          // After specific date

// Label-based queries
client.set_query("label:promotions");        // Has promotions label
client.set_query("-label:important");        // Does NOT have important label

// Content queries
client.set_query("subject:newsletter");      // Subject contains "newsletter"
client.set_query("from:noreply@example.com"); // From specific sender

// Combined queries
client.set_query("label:promotions older_than:6m -is:starred");

Performance & Limits

Pagination

• Default page size: 200 messages
• Use client.set_max_results(n) to adjust
• Use client.get_messages(0) to get all pages
• Use client.get_messages(n) to limit to n pages

Rate Limits

• The library uses the official google-gmail1 crate
• Built-in retry logic for transient errors
• Respects Gmail API quotas and limits

Batch Operations

• Batch delete/trash operations are more efficient than individual calls
• Operations are atomic - either all succeed or all fail

Logging

The library uses the log crate for logging:

use env_logger;

// Initialize logging
env_logger::init();

# Set log level via environment variable
# RUST_LOG=cull_gmail=debug cargo run

Log levels:

• error: Critical errors
• warn: Warnings (e.g., missing labels, dry-run mode)
• info: General information (e.g., message subjects, action results)
• debug: Detailed operation info
• trace: Very detailed debugging info

Security Considerations

OAuth2 Token Storage

• Tokens are stored in ~/.cull-gmail/gmail1 by default
• Tokens are automatically refreshed when expired
• Revoke access in Google Account settings

Required Scopes

The library requires the https://mail.google.com/ scope for full Gmail access.

OAuth2 File Security

• Store OAuth2 credential files securely (not in version control)
• Use restrictive file permissions (600)
• Consider using environment variables in production

Troubleshooting

Authentication Issues

1. Verify OAuth2 credential file path and JSON format
2. Check OAuth2 client is configured for "Desktop Application"
3. Ensure redirect URI matches configuration
4. Clear token cache: rm -rf ~/.cull-gmail/gmail1

No Messages Found

1. Verify label names exist: client.show_label()
2. Test query syntax in Gmail web interface
3. Check for typos in label names or query strings

Rate Limiting

1. Reduce page size: client.set_max_results(100)
2. Add delays between operations
3. Check Gmail API quotas

See Also

• CLI Documentation - Complete guide to the command-line interface
• Examples Directory - Additional code examples and sample configurations
• API Documentation - Generated API reference
• Repository - Source code and issue tracking

License

By contributing to cull-gmail, you agree that your contributions will be licensed under the MIT License. This means:

• You grant permission for your contributions to be used, modified, and distributed under the terms of the MIT License
• You confirm that you have the right to submit the code under this license
• You understand that your contributions will become part of the project and available to all users under the MIT License

Contribution

Thank you for your interest in contributing to cull-gmail! We welcome contributions from the community and appreciate your help in making this project better.

Further details can be found in the contribution document.