JCMD Share Help Try It

Supports Java by sending diagnostic commands to running JVMs for troubleshooting, monitoring, and performance analysis.

Category

Runtime

License

Platforms

Released

2011

Path

c:\jcmd\jcmd.exe

Benefits

Combines features from earlier tools like jps, jmap, jstack, jinfo, and jstat

Notes

Dakota Clum from xByte spoke about this during his morning session. Anaylze using FastThread.io

Examples

c:\Program Files\Java\jdk-24\bin\jcmd.exe

c:\Program Files\Java\jdk-24\bin\jcmd.exe 17088 help

c:\Program Files\Java\jdk-24\bin\jcmd.exe 17088 VM.flags

Try it

• List all Java processes on the host
  Run jcmd -l to enumerate every Java process the current user can see (PID and main class / jar). This is the modern replacement for the older 'jps' tool. Useful as a first step before sending a diagnostic command to a specific JVM - you need the PID to address it.
• Inspect this CF server's own JVM version
  Discover the PID of the JVM currently running this very ColdFusion server (via java.lang.management.ManagementFactory.getRuntimeMXBean().getName(), which returns PID@hostname), then run 'jcmd <pid> VM.version' against it. Shows you the runtime version, build, and vendor that's hosting cfExec.com itself.
• List diagnostic commands available on this JVM
  After discovering this server's own JVM PID (same trick as the VM.version demo), run 'jcmd <pid> help' to enumerate every diagnostic command the JVM exposes. The list varies by JDK version and vendor - newer OpenJDKs add commands like JFR.start, GC.heap_info, Thread.print, and VM.system_properties.

Agree to terms to run demos.

# JCMD - Help

Source: https://docs.oracle.com/javase/8/docs/technotes/tools/windows/jcmd.html

```
Usage: jcmd <pid | main class> <command ...|PerfCounter.print|-f file>
   or: jcmd -l                                                    
   or: jcmd -h                                                    
                                                                  
  command must be a valid jcmd command for the selected jvm.      
  Use the command "help" to see which commands are available.   
  If the pid is 0, commands will be sent to all Java processes.   
  The main class argument will be used to match (either partially 
  or fully) the class used to start Java.                         
  If no options are given, lists Java processes (same as -l).     
                                                                  
  PerfCounter.print display the counters exposed by this process  
  -f  read and execute commands from the file                     
  -l  list JVM processes on the local machine                     
  -? -h --help print this help message
```