if statement

if(Boolean_expression) {
   // Statements will execute if the Boolean expression is true
}

if somecommand; then
  # do this if somecommand has an exit code of 0
fi

if(Boolean_expression) {

if(Boolean_expression) {
   // Statements will execute if the Boolean expression is true
}
If the Boolean expression evaluates to true then the block of code inside the if statement will be executed. If not, the first set of code after the end of the if statement (after the closing curly brace) will be executed.