Demonstration of how to do environment variable substitution with buildkite-agent 2.x (in 3.x env var support is built-in)

pipeline.bash

#!/bin/bash

set -euo pipefail

# Demonstration of how to do environment variable substitution with
# buildkite-agent 2.x (in 3.x env var support is built-in)
#
# To use, save this file as .buildkite/pipeline.bash, chmod +x, and
# then set your first pipeline step to run this and pipe it into
# pipeline upload:
#
# .buildkite/pipeline.sh | buildkite-agent pipeline upload
#

cat << EOF
steps:
  - trigger: "another-pipeline"
    build:
      message: "Deploying build $BUILDKITE_BUILD_NUMBER"
      commit: "$BUILDKITE_COMMIT"
      branch: "$BUILDKITE_BRANCH"
      env:
        SOME_ENV: "$SOME_ENV"
EOF

Alternatively you could use the following pipeline upload step:

( echo "cat <<EOF" ; cat .buildkite/pipeline.yml ; echo EOF ) | sh | buildkite-agent pipeline upload

@toolmantim .buildkite/pipeline.sh | buildkite-agent pipeline upload works great for me (adding the cat EOF stuff), but when I try ( echo "cat <<EOF" ; cat .buildkite/pipeline.yml ; echo EOF ) | sh | buildkite-agent pipeline upload on a regular pipeline file, it goes into an infinite loop and duplicates all the steps in the pipeline continuously