This repo contains a standard library for use within Heroku Buildpacks.

It allows for unified output methods, some common buildpack utilities, and facilitates metrics logging.

In your buildpack, add the following line (towards the top):

source /dev/stdin <<< "$(curl -s --retry 3 https://lang-common.s3.amazonaws.com/buildpack-stdlib/latest/stdlib.sh)"

Or, if you want to pin to a specific release:

source /dev/stdin <<< "$(curl -s --retry 3 https://lang-common.s3.amazonaws.com/buildpack-stdlib/v4/stdlib.sh)"

Or, if you are going to run the code multiple times in your source (e.g. in a utils file that gets sourced multiple times):

if [[ ! -f  /tmp/stdlib-v8.sh ]]; then
  curl --retry 3 -s https://lang-common.s3.amazonaws.com/buildpack-stdlib/v8/stdlib.sh > /tmp/stdlib-v8.sh
fi
source /tmp/stdlib-v8.sh

We recommend pinning to a specific release, for stability reasons.

This will make the following functions available:

Standard output:

• puts_step, which outputs a build step in a standardized format.
• puts_error, which outputs a build error in a standarized format.
• puts_warn, which outputs a build warning in a standardized format.
• puts_verbose, which outputs a build step if the environment variable BUILDPACK_VERBOSE is set.
• is_verbose, which returns 0/1, depending on if it's appropriate to use verbose output or not.

Buildpack utilities:

• set_env, which writes an environment variable to a profile and export script (for multi-buildpack support).
• set_default_env, which writes a default environment variable to a profile and export script (for multi-buildpack support).
• un_set_env, which unsets a user-provided environment variable via profile script.
• sub_env, which launches a subshell with user-provided config.
• export_env, which exports user-provided config into the current shell.

Metrics (only available to Official Heroku Buildpacks):

• nowms, which returns the current time in millesconds.
• mtime, which measures time elapsed for a specific build step.
• mcount, which logs a count for a specific build step.
• mmeasure, which logs a measure for specific build step.
• munique, which logs a unique measurement build step.
• mcount_exit, which logs an exit event and exits 1.

Please see the contents of stdlib.sh for more usage details (including required environment variables).

Fetch the repo from GitHub:

• $ git clone git@github.com:heroku/buildpack-stdlib.git
• $ cd buildpack-stdlib

Upload the stdlib to Amazon S3:

• $ git remote add heroku https://git.heroku.com/buildpack-stdlib.git
• $ git push heroku master
• $ heroku run python upload.py

Notice the version number outputted, then tag it in Git and push that to GitHub:

• $ git tag v42
• $ git push --tags

Don't forget to update HISTORY.txt!