What is the `expr` command?

The expr command is a Unix/Linux utility used for evaluating expressions and performing basic arithmetic operations in the terminal. It can handle integer arithmetic, string operations, and logical comparisons.

Basic Usage:

• Arithmetic Operations: You can perform addition, subtraction, multiplication, and division.
• Syntax: The general syntax is:

  expr <expression>

Examples:

1. Addition:

   expr 5 + 3  # Outputs: 8

2. Subtraction:

   expr 10 - 4  # Outputs: 6

3. Multiplication:

   expr 6 \* 7  # Outputs: 42 (note the backslash before *)

4. Division:

   expr 20 / 4  # Outputs: 5

Important Notes:

• Ensure there are spaces around operators.
• For multiplication, use a backslash (\) before the asterisk (*) to avoid shell interpretation.

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