Lab materials
- Slides: Command line arguments
- Sample calculator program [windows] [linux]
- Code sample: Accepting arguments at runtime
Lab tasks
For this lab, you will have one main task with 2 advanced tasks that add extra functionality and features to the base task.
Lab task: calculator
For this task, you will build a calculator that works by getting its input from the command line
Requirements
- You will create a simple calculator, that
- can do addition, subtraction, multiplication and division
- supports positive integers as operands
- only does one operation at a time (e.g. 3 + 6)
- Have a precision of 2 places after the comma
- Both the operands and the operator will be given as command line arguments
- E.g. an addition operation would look like this:
- Program is not allowed to ask for any input during its execution
- Your calculator must detect the following errors
- Wrong argument count
- Unknown operator
- Non-numeric operand
- Division by zero
- When an error occurs, you will both present the specific error message and the guide how to use your program
Recommended list of functions
- Display help
- Shows how to use the program
- Argument check
- Checks for number of operands
- In advanced, checks for --help argument
- Error management
- Displays the specific error message
- Calls the display help function
- Operand check
- Checks if the operand is numeric
- Returns the operand converted to a number (e.g. int)
- Calculation
- Identifies the operation and calculates the answer
- Returns the answer
You may also benefit from creating a function to check for the operator.
Example
To test a completed program, we recommend downloading the sample and seeing how it works.
To see all the test cases for the program, check the next paragraph.
Example 1: Input is OK and the program prints the answer
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risto@risto-lt3-tux:~$ ./calculator 1 / 4 > 0.25 |
Example 2: Program is executed without arguments. An error message and a how to use guide is provided.
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risto@risto-lt3-tux:~/Desktop$ ./calculator Error 0! Invalid argument count or unknown argument(s) Usage: ./calculator operand operation operand Possible operations: + add - subtract * multiply / divide Note, that due to how shell works, the multiplication operator has to be encased in quotes e.g. 2 "*" 3.5 |
Test cases
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# base case, normal operations ./calculator 1 + 1 ./calculator 7 / 5 # base case, incorrect input ./calculator # wrong argument count ./calculator 1 2 3 4 5 # wrong argument count ./calculator 6 + a # non-numeric operand ./calculator 6 +- 5 # unknown operation ./calculator 6 + 6a # non-numeric operand ./calculator 6 n 6 # unknown operation ./calculator 6 / 0 # division by zero # advanced, normal operation ./calculator 3.0 / 5.0 ./calculator -3.0 / 5.0 # advanced, incorrect input ./calculator 5.5.5 / 5 ./calculator -5-5 / 5 ./calculator 5-5 / 5 |
Advanced task 1: real numbers
Change your program in a way that it would support all real numbers. You must add support for both negative numbers and numbers with decimal places.
Test the following
- -3.3
- 3-3
- -3-3
- 3.3.3
Advanced task 2: Extended functionality
Add the following functionality to your program
- Taking a square root
- Power function (xy)
- Displaying help using the argument --help without causing an error to occur.
All added functions must be present when help is shown.
After the class, you should be able to
- Understand what a command line argument is
- Know other programs that use command line arguments
- Be able to accept command line arguments in C code
- Know that main() function has multiple forms
- Understand what argument count is
- Understand what argument vector is
- Know what is the first argument passed to a program
- Know how argument count changes depending on how many arguments are passed
- Understand that * and [] interchangeable
- Understand what * means in the command prompt and how to pass such characters to programs
- Understand how to pass multiple words as a single argument
- Be able to convert strings into integers, floats