shell use variable in command code example

Example 1: shell script variable

TEXT="Hello World!"
echo $TEXT
# ouput: Hello World!

Example 2: assing a linux xommant to a variab;e

variable_name=$(command)
OR
FILES=`sudo find . -type f -print | wc -l`

Example 3: bash variable in string

${!var}	#Just use to use reference value inside another variable ;)