Append a file, output to screen and redirect from stderr all at once, without tee

Question

I'm running a time dd command in a shell script, and I'd like to output the results to a file, and print it out on the screen. The line that I'm currently running is:

(time dd of=$dest_filepath if=$src_filepath bs=$block_size count=$block_count) >> $log_file 2>&1 &

Although that is leaving me with an empty file and doesn't output to screen. What would I need to do in order to do all three things?

Note that I'm running this in an embedded system with a Busybox installation which does not include tee so this isn't a duplicate of this question.

Answer 1

What you're showing works as expected on my system. Are you sure you're using bash and not sh? In any case, I tried with dash and with busybox's sh and it worked there too. In the absence of tee, I think the only solution will be to cat $logfile after the command is finished.

Another possibility would be to make a link to busybox called tee and attempt to run that. The busybox that came with my Debian supports that but I don't know if yours will:

ln -s /bin/busybox /bin/tee

Then, try running tee normally.

If you really can't get tee, your only other option would be something like this:

foo=$( ( time dd if="file1" of="file2" bs=12 count=5 ) 2>&1 &)
echo "$foo"
echo "$foo" >> logfile

Answer 2

You can use the tee command. Here i have grouped the commands time and dd using the code block so that they will be treated as a single command and their output can be handled easily.

{ time dd of=$dest_filepath if=$src_filepath bs=$block_size count=$block_count; } 2>&1|tee $log_file

Make note of the ; at the end of the second command. This is mandatory for code blocks to work.

Incase if you dont want to use tee then you might think about this

{ time dd of=$dest_filepath if=$src_filepath bs=$block_size count=$block_count; } 2>&1 &> $log_file;cat $log_file