Bash Variables

According to convention it should be in all caps
Variable names cannot start with digits
There shouldn’t be any space between the variable name, = sign and the value

NAME_01="David"
SPORT="Foot"
echo "My name is $NAME_01"

The {} is used to make the command inside it be executed first and its value is used in place of the {}

echo "The best sport is {$SPORT}ball"
foo=bar
echo $foo (bar)

NOTE

• Shell commands are space sensitive
• foo = bar will throw error
• Shell thinks that you are trying to call a function called foo with parameters = and bar

# ${string: offset: length}
number = 12313.12
 
${number:0:4}
# 1231

Double Quotes vs. Single Quotes

Double Quotes the string is expanded

echo "Value : $foo"
# Value : bar

The String is not expanded with single quotes

echo 'Value : $foo'
# Value : $foo