Bash redirect output to tty and file

Question

I'm trying to log some part of script execution. Logs should be displayed at second tty, and also written to a log file.

I can do it with a simple:

echo "Hello log" > /dev/tty2
echo "Hello log" > /var/log/my_logs

But it is very uncomfortable. I could also redirect echo to a particular place:

exec 1<>/var/log/my_logs
exec 2>&1

But how can I redirect STDOUT to both /dev/tty2 and /var/log/my_logs at once?

Answer 1

Use tee.

echo "Hello log" | tee /dev/tty2 /var/log/my_logs > /dev/null

(The final redirection is to prevent the output from appearing to standard output as well. You could also use echo "Hello log" | tee /dev/tty2 > /var/log/my_logs; there's no real difference between the two. tee just writes it standard input to both standard output and one or more named files.)

To redirect all of standard output to the pair, use a process substitution with exec.

exec > >(tee /dev/tty2 /var/log/my_logs)