How can we count/list all files opened by a specific program/COMMAND? [duplicate]

Question

We can list only files opened by a specific PID as

lsof -p 1000
lsof -p 1000 | wc -l

How can we list/count the files opened by a specific program/COMMAND (e.g., java)?

And so much better, if we can group the number of open files for each program. I want to inspect which programs have high numbers of opened files.

I want something like

lsof -c "java" # -c is an imaginary argument similar to -p for process

I use Ubuntu 20.04.

Answer 1

I don't think there is an argument for such a thing implemented on lsof and I don't know what flags are available on your lsof binary.
I think you could achieve what you want with something like this, maybe replacing the head with a 'grep java':

lsof | awk '{print $1}' | sort | uniq -c | sort -rn | head

lsof: Basically I'm listing all the opened files
awk '{print $1}': printing only the first column which is the process name
sort: you need to sort before applying uniq otherwise it will split the count, so java may appear several times depending on the order lsof prints.
uniq -c: group by process name and count lines
The last 2 are for readability.

The problem with this is that all the java instances will be combined, I suppose you could apply the same logic for PIDs and then filter your java instances and child processes by PID.

Hope it helps.