To get get result of command you need to use command substitution (bash feature). Command substitution provides executing a bash command/commands and store its output to variable.
You can use special backticks (``). Everything what you write between backticks is executed by the shell before main command is executed. Sometimes people call them backquotes. Surely you know that they're under [Esc] key.
In this example, we get date into variable:
DATE=`date -I` echo $DATE
If you expect multi-line output, and you would like to display it, it is good practice to use double quotes. In this example, we get all files in /etc into variable FILES:
FILES=$(ls /etc -l) echo "$FILES"
What if you want to use backticks into backticks? It is a little trouble. The solution is to use dollar with brackets $(). This example does the same:
DATE=$(date -I) echo $DATE
It is also possible to use inner way. In next example, output of date will be used as first echo argument:
echo `date -I`
We prepared for you video course Marian's BASH Video Training: Mastering Unix Shell, if you would like to get much more information.
Thank you. Marian Knezek