The if statement uses the exit status of the given command and conditionally executes the statements following. The general syntax is:
if test then commands (if condition is true) else commands (if condition is false) fi
then, else and fi are shell reserved words and as such are only recognised after a newline or ; (semicolon). Make sure that you end each if construct with a fi statement.
if statements may be nested:
if ... then ... else if ... ... fi fi
The elif statement can be used as shorthand for an else if statement. For example:
if ... then ... elif ... ... fi