How to add a progress bar to a shell script?

Question

When scripting in bash or any other shell in *NIX, while running a command that will take more than a few seconds, a progress bar is needed.

For example, copying a b

Answer 1

This lets you visualize that a command is still executing:

while :;do echo -n .;sleep 1;done &
trap "kill $!" EXIT  #Die with parent if we die prematurely
tar zxf packages.tar.gz; # or any other command here
kill $! && trap " " EXIT #Kill the loop and unset the trap or else the pid might get reassigned and we might end up killing a completely different process

This will create an infinite while loop that executes in the background and echoes a "." every second. This will display . in the shell. Run the tar command or any a command you want. When that command finishes executing then kill the last job running in the background - which is the infinite while loop.