Thread: Weird string output only for first run

When calling the following function for the first time, the string it prints out is some weird ANSII characters. However, when I call on the function subsequently with the exact same variables, it gives the answer.

I understand that my code may not be the best way to do the required task. However I would like to understand why the function does not work on the first run but works on the subsequent runs.

Does this have anything to do with fflush ?

Code:

/* function call */
printf("\"%s\" is the midstr of \"%s\" from the position %d with length %d.\n" , midstr( str2 , str1 , start , len ) , str1 , start , len );

char *midstr( char *str2 , const char *str1 , int start , int len )
/* This function aims to copy a string of length len from str1 to str2 starting from start */ 
{
        char string[80] = {0};
        int count = 1 , reduce , j;

        while ( *str1 != '\0' ){
                count++;
                str1++;
        }

        if ( start > count || (start + len) > count ) {
                *str2 = NULL ;
                return str2;
        }

        else {
                reduce = count - start - len + 1;
                str1 -= reduce;
                string[len] = '\0';

                while ( len > 0 ) {
                        printf("1%c\n" , *str1);
                        string[len - 1] = *str1 ;
                        len--;
                        str1--;
                        printf("%c\t" , string[len]);
                }

               }

        str2 = string;
 
        return str2;
}