BASH: how to perform arithmetic on numbers in a pipe

Question

I am getting a stream of numbers in a pipe, and would like to perform some operations before passing them on to the next section, but I\'m a little lost about how I would go

Answer 1

I'd write:

echo "1 2 3 4 5" | {
  for N in $(cat); do
    echo $((N ** 2))
  done | xargs
}

We can think of it as a "map" (functional programming). There are a lot of ways of writing a "map" function in bash (using stdin, function args, ...), for example:

map_stdin() {
  local FUNCTION=$1
  while read LINE; do
    $FUNCTION $LINE
  done
}

square() { echo "$(($1 * $1))"; }

$ echo "1 2 3 4 5" | xargs -n1 | map_stdin square | xargs
1 4 9 16 25