Reproducible script execution with DataLad

Using datalad run, you can precisely record results of your analysis scripts.

This tutorial was created by Sin Kim.

Github: @kimsin98

Twitter: @SinKim98

In addition to being a convenient method of sharing data, DataLad can also help you create reproducible analyses by recording how certain result files were produced (i.e. provenance). This helps others (and you!) easily keep track of analyses and rerun them.

This tutorial will assume you know the basics of navigating the terminal. If you are not familiar with the terminal at all, check the DataLad Handbook’s brief guide.

Create a DataLad project

A DataLad dataset can be any collection of files in folders, so it could be many things including an analysis project. Let’s go to the Neurodesktop storage and create a dataset for some project. Open a terminal and enter these commands:

$ cd /storage

$ datalad create -c yoda SomeProject
[INFO   ] Creating a new annex repo at /home/user/Desktop/storage/SomeProject
[INFO   ] Running procedure cfg_yoda
[INFO   ] == Command start (output follows) =====
[INFO   ] == Command exit (modification check follows) =====
create(ok): /home/user/Desktop/storage/SomeProject (dataset)

Go in the dataset and check its contents.

$ cd SomeProject

$ ls  code

Create a script

One of DataLad’s strengths is that it assumes very little about your datasets. Thus, it can work with any other software on the terminal: Python, R, MATLAB, AFNI, FSL, FreeSurfer, etc. For this tutorial, we will run the simplest Julia script.

$ ml julia

$ cat > code/hello.jl << EOF
println("hello neurodesktop")

You may want to test (parts of) your script.

$ julia code/hello.jl > hello.txt

$ cat hello.txt
hello neurodesktop

Run and record

Before you run your analyses, you should check the dataset for changes and save or clean them.

$ datalad status
untracked: /home/user/Desktop/storage/SomeProject/code/hello.jl (file)
untracked: /home/user/Desktop/storage/SomeProject/hello.txt (file)

$ datalad save -m 'hello script' code/
add(ok): code/hello.jl (file)
save(ok): . (dataset)
action summary:
  add (ok: 1)
  save (ok: 1)

$ git clean -i
Would remove the following item:
*** Commands ***
  1: clean    2: filter by pattern    3: select by numbers    4: ask each   5: quit   6: help
What now> 1
Removing hello.txt

When the dataset is clean, we are ready to datalad run!

$ mkdir outputs

$ datalad run -m 'run hello' -o 'outputs/hello.txt' 'julia code/hello.jl > outputs/hello.txt'
[INFO   ] == Command start (output follows) =====
[INFO   ] == Command exit (modification check follows) =====
add(ok): outputs/hello.txt (file)
save(ok): . (dataset)

Let’s go over each of the arguments:

  • -m 'run hello': Human-readable message to record in the dataset log.
  • -o 'outputs/hello.txt': Expected output of the script. You can specify multiple -o arguments and/or use wildcards like 'outputs/*'. This script has no inputs, but you can similarly specify inputs with -i.
  • 'julia ... ': The final argument is the command that DataLad will run.

Before getting to the exciting part, let’s do a quick sanity check.

$ cat outputs/hello.txt
hello neurodesktop

View history and rerun

So what’s so good about the extra hassle of running scripts with datalad run? To see that, you will need to pretend you are someone else (or you of future!) and install the dataset somewhere else. Note that -s argument is probably a URL if you were really someone else.

$ cd ~

$ datalad install -s /neurodesktop-storage/SomeProject
install(ok): /home/user/SomeProject (dataset)

$ cd SomeProject

Because a DataLad dataset is a Git repository, people who download your dataset can see exactly how outputs/hello.txt was created using Git’s logs.

$ git log outputs/hello.txt
commit 52cff839596ff6e33aadf925d15ab26a607317de (HEAD -> master, origin/master, origin/HEAD)
Author: Neurodesk User <>
Date:   Thu Dec 9 08:31:15 2021 +0000

    [DATALAD RUNCMD] run hello

    === Do not change lines below ===
     "chain": [],
     "cmd": "julia code/hello.jl > outputs/hello.txt",
     "dsid": "1e82813d-856f-4118-b54d-c3823e025709",
     "exit": 0,
     "extra_inputs": [],
     "inputs": [],
     "outputs": [
     "pwd": "."
    ^^^ Do not change lines above ^^^

Then, using that information, they can re-run the command that created the file using datalad rerun!

$ datalad rerun 52cf
[INFO   ] run commit 52cff83; (run hello)
run.remove(ok): outputs/hello.txt (file) [Removed file]
[INFO   ] == Command start (output follows) =====
[INFO   ] == Command exit (modification check follows) =====
add(ok): outputs/hello.txt (file)
action summary:
  add (ok: 1)
  run.remove (ok: 1)
  save (notneeded: 1)

See Also

  • To learn more basics and advanced applications of DataLad, check out the DataLad Handbook.
  • DataLad is built on top of the popular version control tool Git. There are many great resources on Git online, like this free book.
  • DataLad is only available on the terminal. For a detailed introduction on the Bash terminal, check the BashGuide.
  • For even more reproducibility, you can include containers with your dataset to run analyses in. DataLad has an extension to support script execution in containers. See here.