Input error handling

[annik]

Good day,

I'm new in programming, and trying to write a code in C. The requirement is following - to write a text, and to find frequency of 1 chosen character in it. The main thing is that program should check user input (for example, I want to check if user entered "char" --> then correct, or if entered "int" --> not correct). But the program still doesn't check. So I have:

#include <stdio.h>
int main(){
   char c[1000], ch;
   char i, count=0;
   printf("Enter a text: ");
   gets(c);
   printf("Enter a letter to find it's frequency: ");
   if (scanf("%c",&ch) == 1)
         {                                                
      for(i=0;c[i]!='\0';++i)
         {
         if(ch==c[i])
         ++count;
         }
         
         printf("Frequency of %c = %d", ch, count);    }     
   else
   {
          printf("It's not a letter!");
   }
       
   getch();
}

Am I on my right way using if/else?

Thank you in advance for your help.

[Salem]

That's pretty good for a first attempt.

But you need to stop using gets()
FAQ > Why gets() is bad / Buffer Overflows - Cprogramming.com

Apart from that, try this
if (scanf("%c",&ch) == 1 && isalpha(ch) )
Look in ctype.h for other 'is' functions.

[annik]

@Salem, thank You.

Your offered 'is' function helped now.

About gets(). Well, yes, my sentences were not so big till this moment I will learn more about using fgets(), not pointers.

[rstanley]

About gets(). Well, yes, my sentences were not so big till this moment I will learn more about using fgets(), not pointers.

You should use better variable names. Instead of 'char c[1000]', 'char line[1000]' or something more descriptive. Single letters should be used only for an index or something else trivial.

As for gets(), it should never be used, no matter what the size of the string. Buffer overflow is always possible with gets()! Please use fgets() instead.