====== jcmd ======
  * [[https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/tooldescr006.html|jcmd]]
  * 현재 실행중인 JVM 에 명령을 내려 정보를 보거나 행위를 할 수 있다.

===== 예제 =====
<code sh>
$ jcmd
# java process 목록이 출력됨.
5485 sun.tools.jcmd.JCmd
2125 MyProgram

$ jcmd 2125 help # 혹은 jcmd MyProgram help
# 해당 VM에 대해 실행할 수 있는 명령 목록이 나옴.

2125:
The following commands are available:
JFR.stop
JFR.start
JFR.dump
JFR.check
VM.native_memory
VM.check_commercial_features
VM.unlock_commercial_features
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
Thread.print
GC.class_stats
GC.class_histogram
GC.heap_dump
GC.run_finalization
GC.run
VM.uptime
VM.flags
VM.system_properties
VM.command_line
VM.version
help

$ jcmd MyProgram Thread.print
# Thread.print 명령 실행

$ jcmd MyProgram VM.version
2125:
Java HotSpot(TM) 64-Bit Server VM version 24.45-b08
JDK 7.0_45
</code>

현재 Tomcat 프로세스 전체 JVM 버전 출력하기
<code sh>
jcmd | grep Bootstrap | cut -f1 -d' ' | xargs -I % jcmd % VM.version
</code>

===== 참조 =====
  * [[https://www.javacodegeeks.com/2019/02/jcmd-circa-jdk-11.html|jcmd, Circa JDK 11]]
  * [[https://blog.frankel.ch/openjdk-11-tools-trade/|OpenJDK 11, tools of the trade]]
  * [[https://dzone.com/articles/jvm-tuning-using-jcmd|JVM Tuning Using jcmd - DZone Java]]