How do I use output from awk in another command?

bash awk pipeline
snk picture snk · Aug 10, 2010 · Viewed 20.3k times · Source

So I need to convert a date to a different format. With a bash pipeline, I'm taking the date from the last console login, and pulling the relevant bits out with awk, like so:

last $USER | grep console | head -1 | awk '{print $4, $5}'

Which outputs: Aug 08 ($4=Aug $5=08, in this case.)

Now, I want to take 'Aug 08' and put it into a date command to change the format to a numerical date.

Which would look something like this:

date -j -f %b\ %d Aug\ 08 +%m-%d

Outputs: 08-08

The question I have is, how do I add that to my pipeline and use the awk variables $4 and $5 where 'Aug 08' is in that date command?

Answer

Cascabel picture Cascabel · Aug 10, 2010

You just need to use command substitution:

date ... $(last $USER | ... | awk '...') ...

Bash will evaluate the command/pipeline inside the $(...) and place the result there.

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