How to check heap usage of a running JVM from the command line?

Question

Can I check heap usage of a running JVM from the commandline, I mean the actual usage rather than the max amount allocated with Xmx.

I need it to be commandline beca

Answer 1

For Java 8 you can use the following command line to get the heap space utilization in kB:

jstat -gc  | tail -n 1 | awk '{split($0,a," "); sum=a[3]+a[4]+a[6]+a[8]; print sum}'

The command basically sums up:

• S0U: Survivor space 0 utilization (kB).
• S1U: Survivor space 1 utilization (kB).
• EU: Eden space utilization (kB).
• OU: Old space utilization (kB).

You may also want to include the metaspace and the compressed class space utilization. In this case you have to add a[10] and a[12] to the awk sum.