Make variable visible across steps in Bitbucket pipelines?

I'm afraid, but it seems impossible to share environment variable from one step to another, BUT you can define global environment variables for all steps in the settings of the project under pipelines category.

Settings -> Pipelines -> Repository Variables

For some reason, exported environment variables are not retained between the child items of a "step:" or between the top-level "step:" items (more info about these definitions here). But you can copy all the environment variables to a file, then read them back again, because files are preserved between steps:

1. Share variables between the child items of a "step:"

How to share variables between "script:" and "after-script:"

pipelines:
  default:
    - step:
        script:
          # Export some variables
          - export MY_VAR1="FOO1-$BITBUCKET_BUILD_NUMBER"
          - export MY_VAR2="FOO2-$BITBUCKET_BUILD_NUMBER"
          - echo $MY_VAR1
          - echo $MY_VAR2

          # Copy all the environment variables to a file, as KEY=VALUE, to share to other steps
          - printenv > ENVIRONMENT_VARIABLES.txt

        after-script:
          # If the file exists, read all the previous environment variables
          # from the file, and export them again
          - |
            if [ -f ENVIRONMENT_VARIABLES.txt ]; then
                export $(cat ENVIRONMENT_VARIABLES.txt | xargs)
            fi
          - echo $MY_VAR1
          - echo $MY_VAR2

Note: Try to avoid using strings that have spaces or new line characters in them (for the keys and values). The export command will have trouble reading them, and can throw errors. One possible workaround is to use sed to automatically delete any line that has a space character in it:

# Copy all the environment variables to a file, as KEY=VALUE, to share to other steps
- printenv > ENVIRONMENT_VARIABLES.txt
# Remove lines that contain spaces, to avoid errors on re-import (then delete the temporary file)
- sed -i -e '/ /d' ENVIRONMENT_VARIABLES.txt ; find . -name "ENVIRONMENT_VARIABLES.txt-e" -type f -print0 | xargs -0 rm -f

More info:

• https://www.cyberciti.biz/faq/linux-list-all-environment-variables-env-command/ -- for printenv command
• Set environment variables from file of key/value pairs

2. Share variables between the top-level "step:" items

pipelines:
  default:
    - step:
        script:
          - export MY_VAR1="FOO1-$BITBUCKET_BUILD_NUMBER"
    - step:
        script:
          - echo $MY_VAR1 # This will not work

In this scenario, Bitbucket Pipelines will treat the 2 "step:" items as completely independent builds, so the second "step:" will start from scratch with a blank folder and a new git clone.

So you should share files between steps by using declared artifacts, as shown in the answer by belgacea (19 Dec 2019).

As Mr-IDE and Rik Tytgat explained, you can export your environment variables by writing them to a file and then share this file with a following step as an artifact. One way to do so is to write your variables to a shell script in a step, define it as an artifact and then source it in the next step.

definitions:
  steps:
    - step: &build
        name: Build
        script:
          - MY_VAR="FOO-$BITBUCKET_BUILD_NUMBER"
          - echo $MY_VAR
          - echo "export MY_VAR=$MY_VAR" >> set_env.sh
        artifacts: # define the artifacts to be passed to each future step
          - set_env.sh
    - step: &deploy
        name: Deploy
        script:
            # use the artifact from the previous step
          - cat set_env.sh 
          - source set_env.sh
          - echo $MY_VAR

pipelines:
  branches:
    master:
      - step: *build
      - step:
          <<: *deploy
          deployment: test

NB: In my case, the step which publish set_env.sh as an artifact is not always part of my pipelines. In this case, be sure to check if the file exists in the next step before using it.

- step: &deploy
  name: Deploy
  image: alpine
  script:
    # check if env file exists
    - if [ -e set_env.sh ]; then
    -   cat set_env.sh
    -   source set_env.sh
    - fi