How can i put command output into a variable

Question

Trying to run the following bash script. The output of the following ling fails:

mem = free | grep Mem | awk '{print $4/$2 * 100}'

With the error:

mem: command not found

Answer 1

Like this:

mem=$(free | grep Mem | awk '{print $4/$2 * 100}')

You can also use backticks:

mem=`free | grep Mem | awk '{print $4/$2 * 100}'`

But parentheses are preferred now. More: http://mywiki.wooledge.org/BashFAQ/082