September 1, 2015

stat command

I was working on a shell script today that required determining the user that owned a particular directory. A quick search online led me to this Stack Overflow post. This led me to the following quick command that I could use in a script

CASSANDRA_USER=ls -l /var/lib | grep cassandra | awk '{print $3}'

The second line sets the var USER to either the value in CASSANDRA_USER or to the default string "cassandra" if the previous command did not result in a value. The grep was the weak point and it actually started to fail when another component added a directory to /var/lib that was owned by a user named cassandra.

At this point I was not looking forward to a more complex shell command with awk and then I ran across a better answer to the original question. This involved a command that I had not used before - stat. The solution then became

stat -c %U /var/lib/cassandra

It's simple, to the point and doesn't require more logic to handle other situations. I'll make sure I use the stat command in the future instead of trying to parse the output of the ls command.

Tags: reminder linux
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Dan Hable