[Linux] Visualize parent - child process relationship

$ ps -axf -o pid,ppid,tty,stat,cmd

Credit: Orphan vs Zombie vs Daemon processes

[Linux] sum memory usage of processes with the same name (or sub process)

Use atop. Press p and press m.

Credit: https://unix.stackexchange.com/a/209915

Compress a file before scp from remote server to local

ssh user@host "tar -zcvf - -C /path/to/dir filename" | tar -zxvf -

Note: only use when it's much faster to transfer a compressed file to your machine than transferring the original one.

Credits:
https://superuser.com/a/1354868
https://stackoverflow.com/a/3035446/1032449

[PostgreSQL] How to create read-only standby replica (follower)

This link and this link explain it really well and concise

Useful commands for observe running JVM process

$ jcmd

List running processes

$ jinfo 

Get details of a process

$ jps -lvm

List running processes with params

Clojure how to get JVM options from inside application

(.getInputArguments (java.lang.management.ManagementFactory/getRuntimeMXBean))

Credit: How to get vm arguments from inside of java application?

Clojure has lesser typing error problems than the others well-known dynamic typing languages

Give these snippets a try.

// JS
function foo () {
  bar(1)
}

# Ruby
def foo
  bar(1)
end

; Clojure
(defn foo [] 
  (bar 1))

As you can see from the images below, Clojure doesn't allow you to refer to an undeclared symbol. I believe this takes away quite a bit of typing error issues.