How to plumb together download uncompress untar without writing full downloaded file

When working with large files, it can be inefficient and time-consuming to download the entire file before performing any operations on it. In this article, we will explore three different ways to plumb together the process of downloading, uncompressing, and untarring a file without writing the full downloaded file. We will use the Julia programming language to implement these solutions.

Option 1: Using the HTTP.jl and Tar.jl Packages

The first option involves using the HTTP.jl package to download the file and the Tar.jl package to uncompress and untar it. Here is the code:


using HTTP
using Tar

function download_uncompress_untar(url::AbstractString, target_dir::AbstractString)
    response = HTTP.get(url)
    file = Tar.extract(response.body)
    Tar.extract(file, target_dir)
end

# Usage example
download_uncompress_untar("https://example.com/file.tar.gz", "/path/to/target/dir")

This code uses the HTTP.get() function from the HTTP.jl package to download the file from the specified URL. The response.body contains the downloaded file as a byte array. We then pass this byte array to the Tar.extract() function from the Tar.jl package to uncompress and untar the file. Finally, we extract the contents of the file to the specified target directory.

Option 2: Using the LibCURL.jl and Tar.jl Packages

The second option involves using the LibCURL.jl package, which provides a Julia interface to the libcurl library, and the Tar.jl package. Here is the code:


using LibCURL
using Tar

function download_uncompress_untar(url::AbstractString, target_dir::AbstractString)
    curl = Curl.easy()
    curl.url = url

    file = Tar.extract(curl.perform())
    Tar.extract(file, target_dir)
end

# Usage example
download_uncompress_untar("https://example.com/file.tar.gz", "/path/to/target/dir")

This code uses the Curl.easy() function from the LibCURL.jl package to create a CURL handle. We set the URL to download using the curl.url property. The curl.perform() function performs the download and returns the downloaded file as a byte array. We then pass this byte array to the Tar.extract() function from the Tar.jl package to uncompress and untar the file. Finally, we extract the contents of the file to the specified target directory.

Option 3: Using the Shell.jl Package

The third option involves using the Shell.jl package to execute shell commands directly from Julia. Here is the code:


using Shell

function download_uncompress_untar(url::AbstractString, target_dir::AbstractString)
    run(`curl -s $url | tar -xz -C $target_dir`)
end

# Usage example
download_uncompress_untar("https://example.com/file.tar.gz", "/path/to/target/dir")

This code uses the run() function from the Shell.jl package to execute the shell command “curl -s $url | tar -xz -C $target_dir”. The curl command downloads the file from the specified URL and pipes it to the tar command, which uncompresses and untars the file. The -s option in curl suppresses the progress output. The -xz options in tar specify that the file should be both uncompressed and untarred. The -C option in tar specifies the target directory for extraction.

After exploring these three options, it is clear that Option 1, which uses the HTTP.jl and Tar.jl packages, is the better choice. It provides a more native and efficient way to download, uncompress, and untar files in Julia. Additionally, it offers more flexibility and control over the process compared to the other options.

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