How can I send error output to both stdout and file in bash

Question

If I use this

cmd 2>/var/error.log

Then my error goes to that file but then I can't see on screen.

Is there any way I can simultaneously show it on screen as well as send to file?

Answer 1

This will display both stdout and stderr on the terminal while only sending stderr to err.log :

cmd 2> >(tee err.log >&2)

>(...) is process substitution . (The space between the two consecutive > is essential.) This sends stderr and only stderr to the tee command.

The >&2 causes the error messages remain in stderr. This would be important, for example, if this line occurs inside some script whose stdin or stderr is being redirected. (Hat tip: Chepner.)

Answer 2

cmd 2>&1 | tee /tmp/error.log