Problems with strings (do/while loop and if logic)

Question

This code glitches on two things that I cannot diagnose, but is isolated to the if statement: if (strlen(strA) > 8). Suppose I enter in the string "1234567*aA", the program tells me the password is too long, so then I enter in the string "12345", which then triggers the else if statement: else if (strlen(strA) < 9). But everything in the while loop while (j<=9) gets triggered (the program tells me there is a number, a special character, a lowercase letter, and an uppercase letter) and the do/while loop finishes, and the program prompts me to confirm the password. That's wrong. It should prompt me to enter in the password again.

The second issue I notice is if I enter in a string "1111111111111111111", which is obviously too long, the program says the password is too long, but the entire do/while loop terminates and it asks me to confirm my passcode. It should ask me to enter a password again.

If I take out the if statements: if (strlen(strA) > 8) and else if (strlen(strA) < 9), and just run the while loop: while (j<=9), the program works fine, as long as I don't enter in too many characters in the string.

Can anyone diagnose the problem?

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

int main(void) {
    char strA[10];
    char strB[10];
    char strC[] = {'1','2','3','4','5','6','7','8','9','0'};
    char strD[] = {'!','@','#','$','%','^','&','*','(',')'};

    char strE[] = {'a','b','c','d','e','f','g','h','i','j','k',
                   'l','m','n','o','p','q','r','s','t','u','v',
                   'w','x','y','z'};

    char strF[] = {'A','B','C','D','E','F','G','H','I','J',
                   'K','L','M','N','O','P','Q','R','S',
                   'T','U','V','W','X','Y','Z'};
    int i, j, k;
    do {
        k = 0;
        j = 0;

        printf("Please enter your password: ");
        scanf("%s", &strA);
        printf("%s\n", strA);

       if(strlen(strA) > 8) {
           printf("That password is too long\n");
       }
       else if(strlen(strA) < 9) {
           while (j <= 9) {
               for(i = 0; i <= 9; i++) {
                   if(strA[j] == strC[i]) {
                       printf("there is a number in this string.\n");
                       k++;
                       j = 0;
                       while (j <= 9) {
                           for(i = 0; i <= 9; i++) {
                               if(strA[j] == strD[i]) {
                                   printf("there is a character in this string.\n");
                                   k++;
                                   j = 0;
                                   while(j <= 9) {
                                       for(i = 0; i <= 25; i++) {
                                           if(strA[j] == strE[i]) {
                                               printf("there is a lowercase letter in this string.\n");
                                               k++;
                                               j = 0;
                                               while(j <= 9) {
                                                   for(i=0;i<=25;i++) {
                                                       if(strA[j] == strF[i]) {
                                                           printf("there is an uppercase letter in this string.\n");
                                                           k++;
                                                       }
                                                   }
                                                   j++;
                                              }
                                          }
                                      }
                                      j++;
                                  }
                              }
                          }
                          j++;
                      }
                  }
              }
              j++;
          }
          if(k < 4) {
              printf("Your password must contain at least one uppercase letter, one lowercase letter, a number, and a special character.\n");
          }
      }
    } while(k < 4);

    printf("Please confirm your password: ");
    scanf("%s",&strB);

    while(strcmp(strA, strB) != 0) {
        printf("%s\n",strB);
        printf("Your passwords do not match.\nPlease confirm your password: ");
        scanf("%s",&strB);
    }

    putchar('\n');
    printf("%s\n", strA);
    printf("%s\n", strB);

    return 0;
}

If password lenght is too big, why doesn't break the while loop? It will save one "else" — Broken_Window
– Broken_Window, Commented Mar 19, 2014 at 19:46

Richard J. Ross III · Accepted Answer · 2014-03-19 19:41:13Z

2

I think following line is creating the problem:

char strA[10];

char strB[10];

Initialize with default values

memset(&strA,'\0', sizeof(strA));
memset(&strB,'\0', sizeof(strB));

edited Mar 19, 2014 at 19:41

Richard J. Ross III

55.7k25 gold badges139 silver badges205 bronze badges

answered Mar 19, 2014 at 19:39

Mantosh Kumar

5,7533 gold badges26 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

13 Comments

Richard J. Ross III Over a year ago

You dropped this: ).

alk Over a year ago

Or just do: char strA[10] = ""; However +1

user3399201 Over a year ago

This worked for the first problem! However, if I put way too many characters in the first string, it still skips out of the do/while loop.

alk Over a year ago

@user3399201: Just exactly tell scanf() what (not) to do: scanf("%9s",&strA); So it will read a maximum of 9 characters, and there will not overflow, and there will not invoke undefined behaviour.

M.M Over a year ago

@alk and @user3399201 - the scanf argument should be strA, not &strA. It is the address of the first character that is needed, not the address of the entire array. (On most systems it will appear to work anyway to do &strA, but the correct thing to do is strA, or equivalently, &strA[0]

|

Community · Accepted Answer · 2017-05-23 10:31:48Z

2

Look at ASCII standards : there is a faster way to test if a char c is a digit (c>47 && c<58)! http://en.wikipedia.org/wiki/ASCII

More : look at ctype.h as stated here Determine if char is a num or letter

http://www.cplusplus.com/reference/locale/isalpha/

isalpha(c) : true if letter

isdigit(c) : true if digit

``isupper(c)` : true if upper case

islower(c) : true if lower case

Bye,

Francis

edited May 23, 2017 at 10:31

CommunityBot

11 silver badge

answered Mar 19, 2014 at 20:00

francis

9,8672 gold badges30 silver badges43 bronze badges

3 Comments

user3399201 Over a year ago

nice, I'll look into it.

M.M Over a year ago

These macros work even on a non-ASCII system (i.e. you can use them regardless of what ASCII standards say)

francis Over a year ago

@MattMcNabb: I learned something ! Thanks ! The documentation cplusplus.com/reference/cctype/isalnum states : "In C++, a locale-specific template version of this function (isalnum) exists in header <locale>". But it seems also true in C locale.h: cplusplus.com/reference/clocale states "In <cctype> (<ctype.h>), all functions except isdigit and isxdigit are affected by the extended character set selected."

Collectives™ on Stack Overflow

Problems with strings (do/while loop and if logic)

2 Answers 2

13 Comments

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

13 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related