Save the shell command as a variable

1. The command is placed in the "(General keyboard 1 to the left of the key), such as

   Echo ' DMESG | grep ETH '

2. The command is placed in $ (), such as

   echo $ (DMESG | grep eth)

Can be saved to the variable varname as follows
Varname= ' DMESG | grep ETH '
If multiple rows are returned, they can be saved to the array
Array= ($ (DMESG | grep eth))
Then use the For loop to get the values in the array
len=${#array [@]}
for ((i=0; i< $len; i++))
Do
oneline=${array[$i]}
Done

Save the shell command as a variable