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Better Than BASH: Scripting Kotlin
The presentation discusses the advantages of using Kotlin for scripting and automation in software projects, emphasizing its modern tooling and productive ecosystem. It outlines common use cases such as CI/CD, API interactions, and ad hoc tasks, while also introducing the kscript tool for simplifying script execution. The presentation highlights the limitations of Kotlin scripting and compares it to kscript for standalone scripts, advocating for Kotlin as a powerful alternative to traditional scripting languages.
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Better Than BASH: Scripting Kotlin
- 1. Better than BASH- Scripting & Automation with Kotlin October 7–10, 2019 Austin Convention Center Ollie Hughes - Staff Software Engineer - Pivotal @olliehughes82
- 2. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ What 3 things do you find in every software project?
- 3. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ • At least one caffeine addict • At least one Magic the Gathering player • At least one Bash / Powershell / DOS or Perl script over 50 lines long 3
- 4. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ What kind of things do we still write scripts for?
- 5. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ • Continuous Integration & Deployment (CI /CD) • Publishing artefacts • Interacting with CLI tools • AdHoc manual or repetitive tasks. • Generating a report for the boss from issue tracker • Interacting with APIs 5
- 6. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Choosing the right tool
- 7. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ • Creating cloud / IaaS resources ➡ Terraform / Cloud Formation / … • Creating archives from build artefacts ➡ Maven / Gradle / … • Re-inventing the wheel - not using pre-built tools such as Concourse Resources or well supported Jenkins plugins Scripting Anti-Patterns 7
- 8. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ We can do better! 8 while getopts ":a:" FOUND "${@}"; do case ${FOUND} in a) app_name="${OPTARG}" ;; :) printf "argument missing from -%s optionn" $OPTARG usage exit 2 ;; ?) printf "unknown option: -%sn" $OPTARG usage exit 2
- 9. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ • Modern • Good tooling • Productive • Great ecosystem Why use Kotlin for scripting 9
- 10. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ • Standalone scripts for automation • Supplementing CI pipelines & tools • External configuration / YAML generation • Embedded scripting within an application • Dealing with API calls and serializing JSON Good use cases for Kotlin Scripts 10
- 11. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Hello.kts runner.sh println(“Hello SpringOne”) #!/bin/bash kotlinc -script Hello.kts A basic example 11
- 12. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ A basic example 12
- 13. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 13 ⚠ ⚠ 🐞 Bug alert 🐞 ⚠ ⚠
- 14. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ https://github.com/holgerbrandl/kscript Install with sdkman Install with brew (Mac only) curl -s "https://get.sdkman.io" | bash source ~/.bash_profile sdk install kotlin sdk install kscript brew install holgerbrandl/tap/kscript Simplifying the script execution with kscript 14
- 15. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Simplifying the script execution with kscript 15 Hello.kts #!/usr/bin/env kscript println(“Hello SpringOne”)
- 16. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Importing 3rd party libraries 16 #!/usr/bin/env kscript @file:MavenRepository("jitpack", “https://jitpack.io" SNAPSHOT”) @file:DependsOn(“com.github.kotlin.kotlinx~cli:kotlinx-cli- jvm:-SNAPSHOT”) import kotlinx.cli.*
- 17. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Parsing arguments 17 #!/usr/bin/env kscript for (arg in args) { println("arg: ${arg}") }
- 18. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ • Packaging a script • Inline / eval a script • Load script into IntelliJ IDEA or REPL Other kscript features 18
- 19. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Embedded scripting 19 Spring Cloud Contract Kotlin DSL uses a similar approach KotlinScriptingHost().eval(File(“path/to/script.kts"))
- 20. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Testing Scripts 20 Then test framework has access to script like a normal import @file:Import("path/to/externalScript.kts")
- 21. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Kscript vs Kotlin Scripting Support 21 • Kscript still the better solution for standalone scripts • Kotlin Scripting Support useful for more advanced use cases • See https://github.com/Kotlin/KEEP/blob/master/proposals/scripting- support.md
- 22. Unless otherwise indicated,these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Kotlin Scripting Limitations 22 • JVM startup penalty • Distribution of JVM • Kotlin/Native or GraalVM can solve these issues but dev cost is higher
- 23.