Cannot redirect the ouput of hwclock -r command

Question

I am implementing a shell script and I want to analyse the output shown by hwclock -r (--show) command which displays the RTC time and date.

To do that I tried things like: hwclock -r | grep -v "grep" | grep "error" > /dev/null to see if an error happened while reading RTC registers.

The problem is that output is only and always forwarded to console. I tried to forward output to a file then analyse its content and I also tried to use tee -a command to direct output to both console and a file, but with no success.

Is there a solution to that or an explanation to what is happening with hwclock -r command.

In advance Thank you.

Answer 1

I just solved it by forwarding error messages to a file then make the analysis.

hwclock -r 2> file.txt; grep -v "grep" | grep "error" > /dev/null will do the job.

You omitted file.txt in the first grep.

If you just want to check for "error", with a not too old bash this will also do, in a shorter way:

hwclock -r |& grep error >/dev/null