Input Validation
Part of the Fundamentals section of Coddy's C journey — lesson 35 of 63.
When accepting input from users, it's important to verify that the input is valid before using it in your program.
For integer input validation, you can check the return value of scanf:
int number;
int result = scanf("%d", &number);The scanf function returns the number of items successfully read:
if (result == 1) {
// Input was successfully read
printf("Valid input: %d\n", number);
} else {
// Input was invalid
printf("Invalid input!\n");
}For range validation, use conditional statements after reading the input:
if (number >= 1 && number <= 100) {
printf("Number is within valid range (1-100)\n");
} else {
printf("Number is outside valid range!\n");
}
Challenge
EasyWrite a program that reads an integer from the user and validates it in two ways:
- Check if the input is actually an integer (using scanf's return value)
- Check if the integer is between 10 and 50 (inclusive)
Your program should print:
- "Valid input!" if the input is a valid integer between 10 and 50.
- "Invalid input type!" if the input is not an integer.
- "Out of range!" if the input is an integer but not between 10 and 50.
Cheat sheet
To validate integer input, check the return value of scanf:
int number;
int result = scanf("%d", &number);
if (result == 1) {
// Input was successfully read
printf("Valid input: %d\n", number);
} else {
// Input was invalid
printf("Invalid input!\n");
}For range validation, use conditional statements:
if (number >= 1 && number <= 100) {
printf("Number is within valid range (1-100)\n");
} else {
printf("Number is outside valid range!\n");
}Try it yourself
#include <stdio.h>
int main() {
// Write your code here
return 0;
}
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Fundamentals
3Operators
Arithmetic OperatorsModulo OperatorIncrement/DecrementAssignment OperatorsRelational OperatorsLogical Operators Part 1Logical Operators Part 2Logical Operators Part 3Recap Challenge