Question

I have this:

while read -r line; do echo "hello $line"; read -p "Press any key" -n 1; done < file

hello This is line 1
hello his is line 2
hello his is line 3
hello his is line 4
hello his is line 5
hello his is line 6
hello his is line 7

Why do I not see the prompt “Press any key” ?

Answer 1

Quote from man bash:

-p prompt
   Display prompt on standard error, without a trailing new
   line, before attempting to read any input. The prompt is
   displayed only if input is coming from a terminal.

So, because you read lines from file but not from terminal prompt not displayed.