Why does this accept invalid input?

Question

I have a triangle program in c

#include 

// A function which decides the type of the triangle and prints it
void checkTriangle(int s1, int s         


        

Answer 1

If you want to be able to detect an error with the user's input, such as a line not being a valid decimal integer, then you could do the following:

• Read the input into a buffer using fgets(buffer, size, stdin)
• Use strtoul(buffer, &endptr, 10) to parse the buffer as a decimal integer (base 10), where endptr is a char*
• endptr will point to the first invalid character in buffer, ie. the character after the last one which was successfully parsed
• Now if *endptr == '\0', ie. endptr points to the end of buffer, the whole string was parsed as a valid decimal integer