How to add timestamp to STDERR redirection

Question

In bash/ksh can we add timestamp to STDERR redirection?

E.g. myscript.sh 2> error.log

I want to get a timestamp written on the log too.

Answer 1

I was too lazy for all current solutions... So I figured out new one (works for stdout could be adjusted for stderr as well):

echo "output" | xargs -L1 -I{} bash -c "echo \$(date +'%x %T') '{}'" | tee error.log

would save to file and print something like that: 11/3/16 16:07:52 output

Details:

-L1 means "for each new line"

-I{} means "replace {} by input"

bash -c is used to update $(date) each time for new call

%x %T formats timestamp to minimal form.

It should work like a charm if stdout and stderr doesn't have quotes (" or `). If it has (or could have) it's better to use:

echo "output" | awk '{cmd="(date +'%H:%M:%S')"; cmd | getline d; print d,$0; close(cmd)} | tee error.log'

(Took from my answer in another topic: https://stackoverflow.com/a/41138870/868947)