On Linux, there are commands to view processes running on your system. A process is any ongoing event being managed by the kernel. A process is spawned when you launch an application, but there are also many other processes running in the background of your computer, including programs to keep your system time accurate, to monitor for new filesystems, to index files, and more. The utilities, such as those included in the procps-ng package, that monitor these processes tend to be intentionally generic. They look at all processes on your computer so you can filter the list based on what you need to know.
On Linux, you can view processes with the ps command. It is the simplest way to view the running processes on your system.
$ ps
PID TTY TIME CMD
4486 pts/0 00:00:00 bash
66930 pts/0 00:00:00 psYou can use the ps command to view running Java processes on a system also by piping output to grep.
$ ps ax |grep java
67604 pts/1 Sl+ 0:18 /usr/lib/jvm/java-11-openjdk-11.0.12.0.7-4.fc34.x86_64/bin/java -D[Standalone] -server -Xms64m -Xmx512m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true --add-exports=java.desktop/sun.awt=ALL-UNNAMED --add-exports=java.naming/com.sun.jndi.ldap=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.io=ALL-UNNAMED --add-opens=java.base/java.security=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.management/javax.management=ALL-UNNAMED --add-opens=java.naming/javax.naming=ALL-UNNAMED -Dorg.jboss.boot.log.file=/home/alan/wildfly/24.0.1/standalone/log/server.log -Dlogging.configuration=file:/home/alan/wildfly/24.0.1/standalone/configuration/logging.properties -jar /home/alan/wildfly/24.0.1/jboss-modules.jar -mp /home/alan/wildfly/24.0.1/modules org.jboss.as.standalone -Djboss.home.dir=/home/alan/wildfly/24.0.1 -Djboss.server.base.dir=/home/alan/wildfly/24.0.1/standaloneOpenJDK, however, has its very own specific process monitor. The Java Virtual Machine Process Status (jps) tool allows you to scan for each running instance of the Java Virtual Machine (JVM) on your system.
To view a similar output as seen in the ps command, use the -v option. This is useful, partly because it requires less typing.
$ jps -v
67604 jboss-modules.jar -D[Standalone] -Xms64m -Xmx512m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true --add-exports=java.desktop/sun.awt=ALL-UNNAMED --add-exports=java.naming/com.sun.jndi.ldap=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.io=ALL-UNNAMED --add-opens=java.base/java.security=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.management/javax.management=ALL-UNNAMED --add-opens=java.naming/javax.naming=ALL-UNNAMED -Dorg.jboss.boot.log.file=/home/alan/wildfly/24.0.1/standalone/log/server.log -Dlogging.configuration=file:/home/alan/wildfly/24.0.1/standalone/configuration/logging.propertiesThe default jps output provides the process identifier and the class name or Jar file name of each detected instance.
$ jps
67604 jboss-modules.jar
69430 Jps
Note: The man page for jps states that it is experimental and unsupported. Still, it's a nice-to-have option because often many processes are running on a system, and having a quick way to identify only Java is useful.
Because Java is still a popular language today, being familiar with the Java Development Kit and Runtime Environment remains important. They contain many tools applicable to the development and maintenance of Java applications.
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