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.

Searching for actions

The popper CLI is capable of searching for premade actions that you can use in your workflows.

You can use the popper search command to search for actions based on a search keyword. For example, to search for npm based actions, you can simply run:

$ popper search npm
Matched actions :

> actions/npm

Additionally, when searching for an action, you may choose to include the contents of the readme in your search by using the --include-readme flag.

Once popper search runs, it caches all the metadata related to the search. So, to get the latest releases of the actions, you might want to update the cache using the --update-cache flag.

By default, popper searches for actions from a list present here. To help the list keep growing, you can add Github organization names or repository names(org/repo) and send a pull request to the upstream repository.

To get the details of a searched action, use the popper info command. For example,

popper info popperized/cmake
An action for building CMake projects.

Continuously validating a workflow

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).

Specifying which workflows to run via commit messages

When a CI service executes a popper workflow by invoking popper run on the CI server, it does so without passing any flags and hence we cannot specify which workflow to skip or execute. To make this more flexible, popper provides the ability to control which workflows to be executed by looking for special keywords in commit messages.

The popper:whitelist[<list-of-workflows>] keyword can be used in a commit message to specify which workflows to execute among all the workflows present in the project. For example,

This is a sample commit message that shows how we can request the
execution of a particular workflow.


The above commit message specifies that only the workflow a will be executed and any other workflow will be skipped. A comma-separated list of workflow paths can be given in order to request the execution of more than one workflow. Alternatively, a skip list is also supported with the popper:skip[<list-of-workflows>] keyword to specify the list of workflows to be skipped.

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.