dl

A download manager that uses multiple concurrent connections to speed up downloads.

Features

• Concurrent downloading with configurable connection count
• Resumable downloads (enabled by default)
• Progress tracking that persists across restarts
• Bandwidth limiting
• Checksum verification (MD5, SHA256)
• Retry with exponential backoff

Install

Download

Grab the latest binary from the releases page.

Build from source

Requires Go 1.23+

git clone https://github.com/mgomes/dl.git
cd dl
go build -o dl ./cmd/dl

Usage

dl <url> [url2] [url3] ...

Library usage

package main

import (
	"context"
	"fmt"
	"os"

	"github.com/mgomes/dl"
)

func main() {
	ctx := context.Background()
	downloader := dl.Downloader{
		URI:        "https://example.com/file.zip",
		Context:    ctx,
		WorkingDir: ".",
		Boost:      4,
		Retries:    3,
		Resume:     true,
	}

	if err := downloader.FetchMetadata(); err != nil {
		fmt.Printf("metadata error: %v\n", err)
		os.Exit(1)
	}

	if err := downloader.Fetch(); err != nil {
		fmt.Printf("download error: %v\n", err)
		os.Exit(1)
	}

	fmt.Println("saved to", downloader.OutputPath())
}

Options

-filename string     Custom output filename
-boost int           Number of concurrent connections (default: 8)
-retries int         Max retries per part (default: 3)
-resume              Resume interrupted download (default: true)
-no-resume           Start fresh, ignore any existing progress
-limit string        Bandwidth limit (e.g. 1M, 500K, 100KB/s)
-checksum string     Verify file (format: algorithm:hash)

Examples

# Basic download
dl https://example.com/file.zip

# Custom filename
dl -filename myfile.zip https://example.com/file.zip

# Resume happens automatically. If interrupted, just run again:
dl https://example.com/file.zip

# Force a fresh download
dl -no-resume https://example.com/file.zip

# Limit to 1 MB/s
dl -limit 1M https://example.com/file.zip

# Verify checksum after download
dl -checksum sha256:abc123... https://example.com/file.zip

# Use 4 connections with 5 retries
dl -boost 4 -retries 5 https://example.com/file.zip

Configuration

You can set defaults in ~/.dlrc:

boost = 8
retries = 3

How it works

Concurrent connections

The -boost flag controls how many parallel connections are used. The default of 8 works well for most cases. Going higher usually does not help since your connection will saturate.

Resume

If a download is interrupted, just run the same command again. Progress is saved to a hidden .filename.dl_progress file every 2 seconds. Each part's byte position is tracked independently, so multi-connection downloads resume correctly.

The progress file is deleted after a successful download.

Bandwidth limiting

The -limit flag accepts values like 1M, 500K, or 100KB/s. When using multiple connections, the limit is split evenly between them.

Checksum verification

dl -checksum sha256:e3b0c44... https://example.com/file.zip
dl -checksum md5:d41d8cd9... https://example.com/file.zip

Retries

Failed parts retry with exponential backoff (1s, 2s, 4s). Use -retries to change the max attempts.