This document introduces CRaSH, an extensible command line shell for the Java Virtual Machine (JVM). CRaSH allows users to interact with a JVM using a familiar command line interface and includes built-in commands for JVM monitoring and administration. It can be used both as a standalone shell or embedded within JVM applications. The document outlines CRaSH's features, usage scenarios, and how it compares to traditional Unix shells while running on the JVM.

2. An extensible command line for
the JVM
Julien Viet Alain Defrance
Senior software engineer Software engineer
eXo Platform eXo Platform
@julienviet @alaindefrance

3. @julienviet @alaindefrance
10 years of Open Source 2 years of Open Source
■ eXo Platform 2008 ■ eXo Platform 2010
■ Red Hat 2006 Various
■ JBoss 2002 ■ Develop social product
Various
■ Portal stuff (JBoss / GateIn)
■ JCP a while ago
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4. Project
 Open source LGPL: http://www.crashub.org
 CRaSH 1.0 – April 2012
 CRaSH 1.1 – August 2012
 CRaSH 1.2 – Soon (in release candidate)

5. What/Why?
CLI are still relevant
Ubiquitous
Expressive: find . -name “*.java” -exec grep julien {} ; -
print
Made for us 
Trends: NoSQL, MS Powershell, Drupal, Jenkins, Cloud,
etc…
Fun!

6. Comparison with UN*X shell
Same client interface But hosted by JVM
■ History ■ Java threads
■ Completion ■ JVM access
■ Command Line Editing
■ Options & Arguments
■ Pipes
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7. Usage
Runtime modes Get it from
■ Standalone ■ crashub download
■ Embedded (web app, Spring, ■ Maven Central dependency
…)
■ Attach
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8. Simple stack
Native Client
SSH Telnet Web Console Attach VisualVM
Connectors
CRaSH
Groovy Commands

9. What you can do with CRaSH
 Swiss army knife
 Embed in your runtime
 Create your commands
 Monitoring tool
 Scripting
 And more…

10. Out of the box

11. Out of the box
 Install CRaSH
 Run CRaSH standalone
 CLI basics
 JVM base commands
 Test it online

12. The Swiss Knife

13. The Swiss Knife
 Attach CRaSH to JBoss Application Server
 Execute commands in the Application Server

14. Extend your runtime

15. Extend your runtime
 Embed CRaSH in a Spring web application
 Connect using remote protocol
 Develop a command to access Spring beans
 Add options and arguments to the command

16. Monitoring

17. Monitoring
 Attach to Tomcat with VisualVM
 Use JMX command pipes
 Create pipes
 Assemble in custom dashboard

18. Pipelined object stream
jmx
jmx get sort
find
<Void, ObjectName> <ObjectName, Map> <Map, Map>

19. Wrap up
Multi facet, powerful and extensible
Reach us
crash-users@googlegroups.com
@crashub
http://www.crashub.org
Hackergarten hands on coding Tuesday

20. Q&A