set up global variables dynamically in gitlab-ci

Question

I want to set some variables by getting the values from a pom.xml file. These variables need to be global because they will be used in multiple stages and jobs.

According to the gitlab-ci documentation, I can set global variables in two differents ways:

1. using a variable statement:

   variable:  
    pom_artifactID: $(grep -m1 '<artifactId>' pom.xml | cut -d '<' -f2  |cut -d '>' -f2)
   

2. Using a "before" script:

    before_script:
      - pom_artifactID=$(grep -m1 '<artifactId>' pom.xml | cut -d '<' -f2  |cut -d '>' -f2)
      - pom_artifactVersion=$(grep -m1 '<version>' pom.xml | cut -d '<' -f2  |cut -d '>' -f2)
      - pom_packaging=$(grep -m1 '<packaging>' pom.xml | cut -d '<' -f2  |cut -d '>' -f2)
      - pom_finalName=$({ grep -m1 '<finalName>' pom.xml |  cut -d '<' -f2 | cut -d '>' -f2; [ ${PIPESTATUS[0]} -eq 0 ] && true || echo ${pom_artifactID}-${pom_artifactVersion}.$pom_packaging}; })
   

The first doesn't work because gitlab-ci doesn't evaluate $(command), so pom_artifactID becomes a literal "$(grep -m1 '' pom.xml | cut -d '<' -f2 |cut -d '>' -f2)"

The second doesn't work either because "before_script" relies on the "grep" command and some docker images used in my pipeline have an old version of grep.

There is another way to set global variables o pass variables between stages and jobs?

Answer 1

Passing values between jobs and stages

There is currently no way in GitLab to pass environment variable between stages or jobs.
But there is a request for that: https://gitlab.com/gitlab-org/gitlab/-/issues/22638

Current workaround is to use artifacts - basically pass files.
We had a similar use case - get Java app version from pom.xml and pass it to various jobs later in the pipeline.

How we did it in .gitlab-ci.yml:

stages:
  - prepare
  - package

variables:
  VARIABLES_FILE: ./variables.txt  # "." is required for image that have sh not bash

get-version:
  stage: build
  script:
    - APP_VERSION=...
    - echo "export APP_VERSION=$APP_VERSION" > $VARIABLES_FILE
  artifacts:
    paths:
      - $VARIABLES_FILE
package:
  stage: package
  script:
    - source $VARIABLES_FILE
    - echo "Use env var APP_VERSION here as you like ..."

 
 

Extracting values from pom.xml

By the way it's better to treat xml.pom as XML to extract values from pom.xml rather than plain grep, because XML elements can potentially span multiple lines.

There are at least a couple of options, examples:

1. Use XPath in xmllint tool from libxml2-utils

get-version:
  image: ubuntu
  script:
    - apt-get update
    - apt-get install -y libxml2-utils
    - APP_VERSION=`xmllint --xpath '/*[local-name()="project"]/*[local-name()="version"]/text()' $POM_FILE`

2. Use python xml processing

get-version:
  image: python3
  script:
    - APP_VERSION=$(python3 -c "import xml.etree.ElementTree as ET; print(ET.parse(open('pom.xml')).getroot().find('{http://maven.apache.org/POM/4.0.0}version').text)")