Worked on the fluent/fluent-bit repository to implement environment variable default value substitution, enabling bash-style fallback values when environment variables are unset or empty. This feature, developed in C, included comprehensive unit tests to ensure reliability and prevent configuration failures in containerized deployments. Documentation in fluent/fluent-bit-docs was updated using Markdown to clearly explain the new ${VARIABLE:-DEFAULT} syntax, with additional improvements for clarity and accuracy. The work focused on aligning code behavior and documentation, enhancing both configurability and user guidance. Technical skills applied included C programming, environment variable management, technical writing, and unit testing, with attention to detail throughout.