Question

This question comes from Pro Bash Programming by Chris Johnson at Chapter 2 Exercises 2:

Write a script, using $RANDOM, to write the following output both to a file and to a variable. The following numbers are only to show the format; your script should produce different numbers:

 1988.2365
13798.14178
10081.134
 3816.15098

Here is my solution:

printf -v var "%5d.%-5d\n" $RANDOM $RANDOM $RANDOM $RANDOM $RANDOM $RANDOM $RANDOM $RANDOM > FILE

It seems that the output directly goes into var, FILE is empty.

My question is that is there a way to redirect standard output to a variable and a file at the same time?

Answer 1

You could write:

var="$(printf '%5d.%-5d\n' $RANDOM ... | tee FILE)"

using the tee command to “split” standard-output, so that it goes both into FILE and into a new standard-output that can be captured in your variable using command substitution.