Practical Examples of Conditional Statements in Bash (GitHub Actions)

Here are concrete examples of the conditional statements, written as if statements in Bash, suitable for GitHub Actions workflows:

Theme: Conditional Flow Based on File Existence

  • Check for docker-compose.test.yml:

  • name: Run Tests with Docker Compose

run: |

if [[ -f docker-compose.test.yml && github.event_name == 'push' ]]; then

docker-compose -f docker-compose.test.yml up -d --build

fi

  • Install Python dependencies if requirements.txt exists:

  • name: Install Python Dependencies

run: |

if [[ -f requirements.txt ]]; then

pip install -r requirements.txt

fi

Theme: Conditional Flow Based on String Comparisons

  • Set environment variable based on branch:

  • name: Set Environment

run: |

if [[ github.ref == 'refs/heads/main' ]]; then

echo "ENVIRONMENT=production" >> $GITHUB_ENV

fi

  • Perform release steps for tagged commits:

  • name: Create Release

run: |

if [[ "${github.ref}" == "refs/tags/"* ]]; then

gh release create ${{ github.ref_name }} --generate-notes

fi

Theme: Conditional Flow Based on Regular Expression Matches

  • Check tag format for version:

  • name: Validate Tag

run: |

if [[ ! "${github.ref}" =~ ^refs/tags/v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then

echo "::error::Invalid tag format. Must be vX.Y.Z"

fi

Theme: Error Handling and Exit Codes

  • Proceed only if tests passed:

  • name: Run Tests

id: run-tests

run: npm test

  • name: Deploy

run: |

if [[ "${{ steps.run-tests.outcome }}" == "success" ]]; then

./deploy.sh

fi

Explanation of && and || within if Statements:

  • &&: Within an if statement, && combines two conditions. The second condition is only evaluated if the first condition is true. If both conditions are true, the entire if statement is true.

  • ||: Within an if statement, || acts as an "or". If either the first or the second condition is true (or both), the entire if statement is true.

Important Note: Remember that GitHub Actions runs scripts with the -e flag, meaning the entire script will fail if any command within it fails. So, you might want to handle potential errors within the if blocks to prevent premature workflow termination.