Course of Raku / Objects, I/O, and exceptions / Input and output / Standard streams / Exercises

Output and error

Problem

A program adds up the list of numbers 3, 5, 7 in a loop. On every cycle, send the current running total to standard error as a progress message, and after the loop send the final result to standard output, using the stream handles directly.

This separation matters: the result can be captured or piped onward, while the progress messages stay out of the way on standard error.

Example

When you run the program, both streams appear on the screen — the running totals, then the final result:

running total: 3
running total: 8
running total: 15
15

But if you discard standard error, only the real result remains:

$ raku output-and-error.raku 2>/dev/null
15

Solution

✅ See the solution

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