Bash If...Else

If Statements

If statements allow you to execute code based on a condition. If the condition is true, the code block will run.

The condition is enclosed in square brackets [ ] and the statement ends with fi, which is if spelled backward, marking the end of the if block.

# Basic if statement
num=15
if [ $num -gt 10 ]; then
  echo "Number is greater than 10"
fi

If...Else Statements

If...else statements provide a way to execute one block of code if a condition is true and another block if it is false.

The else keyword introduces the alternative block, and the statement ends with fi.

# If...else statement
num=8
if [ $num -gt 10 ]; then
  echo "Number is greater than 10"
else
  echo "Number is 10 or less"
fi

Elif Statements

Elif statements allow you to check multiple conditions in sequence. If the first condition is false, the next one is checked.

The elif keyword stands for "else if," and the statement still ends with fi.

# If...elif...else statement
num=10
if [ $num -gt 10 ]; then
  echo "Number is greater than 10"
elif [ $num -eq 10 ]; then
  echo "Number is exactly 10"
else
  echo "Number is less than 10"
fi

Nested If Statements

Nested if statements allow you to place an if statement inside another if statement, enabling more complex logic.

Each if block must be closed with its own fi.

# Nested if statement
num=5
if [ $num -gt 0 ]; then
  if [ $num -lt 10 ]; then
    echo "Number is between 1 and 9"
  fi
fi