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

echo 1 2 3 4 5 | xargs -n 1 bash -c 'echo $(($1*$1))' args 

Answer 2

xargs, xargs, xargs

echo 1 2 3 4 5 | xargs -n1 echo | xargs -I NUMBER expr NUMBER \* NUMBER | xargs

Or, go parallel:

squareit () { expr $1 \* $1; }
export -f squareit
echo 1 2 3 4 5 | xargs -n1 | parallel --gnu squareit | xargs

Which would be way simpler if you passed your pipe as a standard set of args:

parallel --gnu "expr {} \* {}" ::: $(echo 1 2 3 4 5) | xargs

Or even:

parallel --gnu "expr {} \* {}" ::: 1 2 3 4 5 | xargs

Really worth taking a look at the examples in the doc: https://www.gnu.org/software/parallel/man.html

Answer 3

echo 1 2 3 4 5|{
  read line; 
  for i in $line;
  do
    echo -n "$((i * i)) "; 
  done; 
  echo
}

The {} creates a grouping. You could instead create a script for that.

Answer 4

Or you can pipe to expression to bc:

echo "1 2 3 4 5" | (
  read line; 
  for i in $line;
  do
    echo $i^2 | bc; 
  done; 
  echo
)