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 like those portable shell scripts but a little disturbed that they fork/exec date(1) for every line. Here is a quick perl one-liner to do the same more efficiently:

perl -p -MPOSIX -e 'BEGIN {$!=1} $_ = strftime("%T ", localtime) . $_'

To use it, just feed this command input through its stdin:

(echo hi; sleep 1; echo lo) | perl -p -MPOSIX -e 'BEGIN {$|=1} $_ = strftime("%T ", localtime) . $_'