check command line input is a number in c

Checking if Command Line Input is a Number in C

To check if the command line input is a number in C, you can use the following steps:

1. Accepting Command Line Input: Accept the command line input as a string.

2. Iterating Through the Input: Iterate through each character of the input string to check if it is a digit.

3. Checking for Number: Use the isdigit function to check if each character is a digit.

4. Handling Decimal Numbers: If the input is a decimal number, handle the decimal point appropriately.

5. Handling Negative Numbers: If the input is a negative number, handle the negative sign appropriately.

6. Validating the Input: Ensure that the input contains only valid characters for a number.

Here's an example of how you can achieve this in C:

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s <number>\n", argv[0]);
        return 1;
    }

    char *input = argv[1];
    int isNumber = 1;
    int decimalPointCount = 0;

    for (int i = 0; i < strlen(input); i++) {
        if (input[i] == '-') {
            if (i != 0) {
                isNumber = 0;
                break;
            }
        } else if (input[i] == '.') {
            decimalPointCount++;
            if (decimalPointCount > 1) {
                isNumber = 0;
                break;
            }
        } else if (!isdigit(input[i])) {
            isNumber = 0;
            break;
        }
    }

    if (isNumber) {
        printf("%s is a valid number.\n", input);
    } else {
        printf("%s is not a valid number.\n", input);
    }

    return 0;
}

This example checks if the command line input is a valid number and handles decimal numbers and negative numbers appropriately.