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Storing and Accessing Build Artifacts

Basics > Storing and Accessing Build Artifacts

This document describes how to work with Artifacts in the following sections:

Artifacts Overview

Artifacts persist data after a job is completed and may be used for longer-term storage of the outputs of your build process.

For example, when a Java build/test process finishes, the output of the process is saved as a .jar file. CircleCI can store this file as an artifact, keeping it available long after the process has finished.

artifacts data flow

Another example of an artifact is a project that is packaged as an Android app where the .apk file is uploaded to Google Play.

If a job produces persistent artifacts such as screenshots, coverage reports, core files, or deployment tarballs, CircleCI can automatically save and link them for you.

artifacts tab screeshot

Find links to the artifacts at the top of the Job page. Artifacts are stored on Amazon S3. There is a 3GB curl file size limit. Artifacts are designed to be useful around the time of the build. It is best practice not to rely on artifacts as a software distribution mechanism with long term future guarantees.

Note: Uploaded artifact filenames are encoded using the Java URLEncoder. Keep this in mind if you are expecting to find artifacts at a given path within the application.

Uploading Artifacts

To upload artifacts created during builds, use the following example:

version: 2
jobs:
  build:
    docker:
      - image: python:3.6.0-jessie

    working_directory: /tmp
    steps:
      - run:
          name: Creating Dummy Artifacts
          command: |
            echo "my artifact file" > /tmp/artifact-1;
            mkdir /tmp/artifacts;
            echo "my artifact files in a dir" > /tmp/artifacts/artifact-2;

      - store_artifacts:
          path: /tmp/artifact-1
          destination: artifact-file

      - store_artifacts:
          path: /tmp/artifacts

The store_artifacts step uploads two build artifacts: a file (/tmp/artifact-1) and a directory (/tmp/artifacts). After the artifacts successfully upload, view them in the Artifacts tab of the Job page in your browser. There is no limit on the number of store_artifacts steps a job can run.

Currently, store_artifacts has two keys: path and destination.

  • path is a path to the file or directory to be uploaded as artifacts.
  • destination (Optional) is a prefix added to the artifact paths in the artifacts API. The directory of the file specified in path is used as the default.

Uploading Core Files

This section describes how to get core dumps and push them as artifacts for inspection and debugging. The following example creates a short C program that runs abort(3) to crash the program.

  1. Create a Makefile with the following lines:

      all:
        gcc -o dump main.c
    
  2. Create a main.c file with the following lines.

      #include <stdlib.h>
         
      int main(int argc, char **argv) {
          abort();
      }
    
  3. Run make and ./dump on the generated program to print Aborted (core dumped)!

Following is a full config.yml that compiles the example C abort program, and collects the core dumps as artifacts.

version: 2
jobs:
  build:
    docker:
      - image: gcc:8.1.0
    working_directory: ~/work
    steps:
      - checkout
      - run: make
      - run: |
          # tell the operating system to remove the file size limit on core dump files 
          ulimit -c unlimited
          ./dump
      - run:
          command: |
            mkdir -p /tmp/core_dumps
            cp core.* /tmp/core_dumps
          when: on_fail
      - store_artifacts:
          path: /tmp/core_dumps

The ulimit -c unlimited removes the file size limit on core dump files. With the limit removed, every program crash creates a core dump file in the current working directory. The core dump file is named core.%p.%E where %p is the process id and %E is the pathname of the executable. See the specification in /proc/sys/kernel/core_pattern for details.

Finally, the core dump files are stored to the artifacts service with store_artifacts in the /tmp/core_dumps directory.

Core Dump File in Artifacts Page

When CircleCI runs a job, a link to the core dump file appears in the Artifacts tab of the Job page.

Downloading All Artifacts for a Build on CircleCI

To download your artifacts with curl, follow these steps.

  1. Create a personal API token and copy it to a clipboard.

  2. In a Terminal window, cd to a directory where you want the artifact files.

  3. Run the commands below, replacing all variables starting with a : with real values for your project. :your_token should be replaced with the token you copied earlier. :vcs-type is dependent on your version control system (either github or bitbucket).

export CIRCLE_TOKEN=':your_token'

curl https://circleci.com/api/v1.1/project/:vcs-type/:username/:project/:build_num/artifacts?circle-token=$CIRCLE_TOKEN | grep -o 'https://[^"]*' > artifacts.txt

<artifacts.txt xargs -P4 -I % wget %?circle-token=$CIRCLE_TOKEN

The curl command fetches all artifact details for a build and pipes it to grep to extract the URLs. The results are saved to the artifacts.txt file. Finally, xargs reads the file and downloads each artifact to the current directory.

In this example, xargs runs four processes to download files in parallel via wget. Adjust the value given to -P to fit your needs.