How to use scanf() function?

Understanding the `scanf()` Function in C

The scanf() function in C is a powerful and widely used input function that allows you to read data from the user or from a file. It is part of the standard input/output (stdio.h) library in C, and it provides a flexible way to parse and store user input.

How to Use `scanf()`

The basic syntax of the scanf() function is as follows:

int scanf(const char *format, ...);

The format parameter is a string that specifies the format of the input data, and the ellipsis (...) represents the variables that will store the input values.

Here's an example of how to use scanf() to read an integer and a floating-point number from the user:

int num;
float price;

printf("Enter an integer and a floating-point number: ");
scanf("%d %f", &num, &price);

printf("You entered: %d and %f\n", num, price);

In this example, the scanf() function reads an integer and a floating-point number from the user, and stores them in the num and price variables, respectively. The %d and %f format specifiers are used to indicate the type of data being read.

It's important to note that the & symbol is used to pass the address of the variables to scanf(), as the function needs to store the input values directly in the variables.

graph TD A[User Input] --> B[scanf() Function] B --> C[Parsed Input Data] C --> D[Stored in Variables]

Handling Input Errors

One of the key features of scanf() is its ability to handle input errors. If the user enters data that doesn't match the expected format, scanf() will return a value indicating the number of successful conversions. This can be used to detect and handle input errors.

Here's an example of how to use scanf() to read an integer and handle input errors:

int num;

printf("Enter an integer: ");
if (scanf("%d", &num) != 1) {
    printf("Error: Invalid input\n");
    return 1;
}

printf("You entered: %d\n", num);

In this example, if the user enters a non-integer value, scanf() will return a value of 0, indicating that no successful conversions were made. The code then prints an error message and returns 1 to indicate an error.

Formatting Options

The scanf() function supports a wide range of format specifiers, which allow you to read different types of data, such as characters, strings, and even custom data structures. Here are some common format specifiers:

%d: Read an integer
%f: Read a floating-point number
%c: Read a single character
%s: Read a string (up to the first whitespace character)
%[...]: Read a string that matches a set of characters

You can also use modifiers with the format specifiers to control the size of the input data, such as %5d to read a 5-digit integer, or %20s to read a string up to 20 characters long.

Conclusion

The scanf() function is a powerful and flexible input function in C that allows you to read data from the user or from a file. By understanding how to use scanf() and its various formatting options, you can write more robust and user-friendly C programs that can handle a wide range of input scenarios.