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

#!/bin/bash

DEBUG=1

LOG=$HOME/script_${0##*/}_$(date +%Y.%m.%d-%H.%M.%S-%N).log
ERROR=$HOME/error.log

exec 2> $ERROR
exec 1> >(tee -ai $LOG)

if [ $DEBUG = 0 ] ; then
    exec 4> >(xargs -i echo -e "[ debug ] {}")
else
    exec 4> /dev/null
fi

# test
echo " debug sth " >&4
echo " log sth normal "
type -f this_is_error
echo " errot sth ..." >&2
echo " finish ..." >&2>&4
# close descriptor 4
exec 4>&-