CLI feautures

New workflow initialization

Create a Git repository:

mkdir mypaper
cd mypaper
git init
echo '# mypaper' >
git add .
git commit -m 'first commit'

Initialize the popper repository and add the configuration file to git:

popper init
git add .
git commit -m 'adds .popper.yml file'

Initialize a workflow

popper scaffold

Show what this did:

ls -l

Commit the “empty” pipeline:

git add .
git commit -m 'adding my first workflow'

Executing a workflow

To run the workflow:

popper run

or to execute all the workflows in a project:

popper run --recursive

Environment Variables

Popper defines the same environment variables that are defined by the official Github Actions runner. To see the values assigned to these variables, run the following workflow:

workflow "env workflow" {
  resolves = "show env"

action "show env" {
  uses = "actions/bin/sh@master"
  args = ["env"]

Reusing existing workflows

Many times, when starting an experiment, it is useful to be able to use an existing workflow as a scaffold for the one we wish to write. The popper-examples repository contains a list of example workflows and actions for the purpose of both learning and to use them as a starting point. Another examples can be found on Github’s official actions organization.

Once you have found a workflow you’re interested in importing, you can use the popper add command to obtain a workflow. For example:

cd myproject/
mkdir myworkflow
popper add
Downloading workflow data-science as data-science...
Workflow docker-data-science has been added successfully.

This will download the contents of the workflow and all its dependencies to your project tree.

Continuously validating a pipeline

The ci subcommand generates configuration files for multiple CI systems. The syntax of this command is the following:

popper ci --service <name>

Where <name> is the name of CI system (see popper ci --help to get a list of supported systems). In the following, we show how to link github with some of the supported CI systems. In order to do so, we first need to create a repository on github and upload our commits:

# set the new remote
git remote add origin <your-github-repo-url>

# verify the remote URL
git remote -v

# push changes in your local repository up to github
git push -u origin master


For this, we need an account at Travis CI. Assuming our Popperized repository is already on GitHub, we can enable it on TravisCI so that it is continuously validated (see here for a guide). Once the project is registered on Travis, we proceed to generate a .travis.yml file:

cd my-popper-repo/
popper ci --service travis

And commit the file:

git add .travis.yml
git commit -m 'Adds TravisCI config file'

We then can trigger an execution by pushing to GitHub:

git push

After this, one go to the TravisCI website to see your pipelines being executed. Every new change committed to a public repository will trigger an execution of your pipelines. To avoid triggering an execution for a commit, include a line with [skip ci] as part of the commit message.

NOTE: TravisCI has a limit of 2 hours, after which the test is terminated and failed.


For CircleCI, the procedure is similar to what we do for TravisCI (see above):

  1. Sign in to CircleCI using your github account and enable your repository.

  2. Generate config files and add them to the repo:

    cd my-popper-repo/
    popper ci --service circle
    git add .circleci
    git commit -m 'Adds CircleCI config files'
    git push


For GitLab-CI, the procedure is similar to what we do for TravisCI and CircleCI (see above), i.e. generate config files and add them to the repo:

cd my-popper-repo/
popper ci --service gitlab
git add .gitlab-ci.yml
git commit -m 'Adds GitLab-CI config file'
git push

If CI is enabled on your instance of GitLab, the above should trigger an execution of the pipelines in your repository.


For Jenkins, generating a Jenkinsfile is done in a similar way:

cd my-popper-repo/
popper ci --service jenkins
git add Jenkinsfile
git commit -m 'Adds Jenkinsfile'
git push

Jenkins is a self-hosted service and needs to be properly configured in order to be able to read a github project with a Jenkinsfile in it. The easiest way to add a new project is to use the Blue Ocean UI. A step-by-step guide on how to create a new project using the Blue Ocean UI can be found here. In particular, the New Pipeline from a Single Repository has to be selected (as opposed to Auto-discover Pipelines).

Visualizing workflows

While .workflow files are relatively simple to read, it is nice to have a way of quickly visualizing the steps contained in a workflow. Popper provides the option of generating a graph for a workflow. To generate a graph for this pipeline, execute the following:

popper dot

The above generates a graph in .dot format. To visualize it, you can install the graphviz package and execute:

popper dot | dot -T png -o wf.png

The above generates a wf.png file depicting the workflow. Alternatively you can use the website to generate a graph by copy-pasting the output of the popper dot command.