what does | bash -s do? any example?
 

I am trying to understand what | bash -s does

$ echo ls| bash -s sdfdsf <--- seems to be same as $echo ls |bash . What is the -s asdf doing?

Te "-s" tells bash to read a command from stdin even though more arguments follow. The "sdfsdf" will be a positional argument to bash, but the command you are passing does not make use of it. Try this:Be sure to use single quotes so that the "$*" is passed literally rather than being expanded (probably to nothing) in the echo command.