A couple of years ago, I was sifting through the manpage for bash. I was at the time looking for something else, but my attention was caught by the section about command substitution, I. E. the art of letting a command be substituted by the output of it's execution. In shells, there are two ways in which this can be accomplished; backticks /backquotes or braces. When I read it, it said backticks were old style. I searched for a bit and found a reference that it was deprecated.