To give a variable the value of the output of a command, one uses back quotes:
sh_prompt> VARI="me"
sh_prompt> echo $VARI
me
sh_prompt> OTHER=`echo $VARI`
sh_prompt> echo $OTHER
me
The output of the command within the back quotes is taken to be the new content of the first variable. Another short example:
sh_prompt> TODAY=`date`
sh_prompt> echo $TODAY
Mon Aug 20 17:35:51 EDT 1990
sh_prompt> echo "today's date is $TODAY"
today's date is Mon Aug 20 17:35:51 EDT 1990
Note that by default, the output of a series of commands is sent to the standard output. If the output is preceded by an = sign, the variable preceding the equal sign takes the value of the output of the command.