Use pstree inside awk command

Question

I want to run pstree on a set of pid which I find using ps

ps -aux | grep ^username | awk '{pstree $2}'

Unfortunately, the output is empty, but if I run the pstree command manually with the same pids I get the desired output. What is wrong with the awk command? Or how do I achieve the desired result by other means?

Answer 1

Use system function in awk like this:

awk '{system("pstree " $2)}'

You can shorten your command to:

ps -aux | awk ' /^username/ { system("pstree " $2) }'