Question

I have the following method to generate a string that has to meet requirements,but I need some sort of clause to loop back to user input if a validation requirement is not met.I know in Java there is a subsequent read but I’m not sure what the code required in C is,also I dont think my else if statment are of correct syntax if anyone can spot the error.Some tips or advice would be helpful,
Thanks.

void validatePass()
{
    FILE *fptr;
    char password[MAX+1];
    int iChar,iUpper,iLower,iSymbol,iNumber,iTotal,iResult,iCount;

    //shows user password guidelines
    printf("\n\n\t\tPassword rules: ");
    printf("\n\n\t\t 1. Passwords must be at least 9 characters long and less than 15 characters. ");
    printf("\n\n\t\t 2. Passwords must have at least 2 numbers in them.");
    printf("\n\n\t\t 3. Passwords must have at least 2 uppercase letters and 2 lowercase letters in them.");
    printf("\n\n\t\t 4. Passwords must have at least 1 symbol in them (eg ?, $, £, %).");
    printf("\n\n\t\t 5. Passwords may not have small, common words in them eg hat, pow or ate.");

    //gets user password input
    printf("\n\n\t\tEnter your password following password rules: ");
    scanf("%s", &password);


    iChar = countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);

    if(iUpper < 2)
    {
        printf("Not enough uppercase letters!!!\n");


    }
    else if(iLower < 2)
    {
        printf("Not enough lowercase letters!!!\n");


    }
    else if(iSymbol < 1)
    {
        printf("Not enough symbols!!!\n");


    }
    else if(iNumber < 2)
    {
        printf("Not enough numbers!!!\n");


    }
    else if(iTotal < 9 && iTotal > 15)
    {
        printf("Not enough characters!!!\n");


    }

    iResult = checkWordInFile("dictionary.txt",password);

    if( iResult == gC_FOUND )
    {
        printf("\nFound your word in the dictionary");
    }
    else if
    {
        printf("\nCould not find your word in the dictionary");
    }

    iResult = checkWordInFile("passHistory.txt",password);
    else if( iResult == gC_FOUND )
    {
        printf("\nPassword used");
    }
    else if
    {
        printf("\nOk to use!");
    }
    else
    {
    printf("\n\n\n Your new password is verified ");
    printf(password);
    }
    //writing password to passHistroy file.


    fptr = fopen("passHistory.txt", "w");   // create or open the file
    for( iCount = 0; iCount < 8; iCount++)
    {
        fprintf(fptr, "%s\n", password[iCount]);
    }

    fclose(fptr);

    printf("\n\n\n");
    system("pause");


}//end validatePass method

Answer 1

Looks like a case for a do {…} while(…) loop.
The “else” you are looking for is just after the dictionary lookup.

Edit:
It would work like this:

do {
  /* read password here */
  ...
  if (condition not met) {
    printf("condition not met!\n");
    continue;
  }
  if (another condition not met) {
    printf("another condition not met!\n");
    continue;
  }
  ...
} while(0);

Edit2:
It might be a good idea to do the testing in another function like this:

bool password_is_safe(char *password)
{
  ...
  if (condition not met) {
    printf("condition not met!\n");
    return false;
  }
  if (another condition not met) {
    printf("another condition not met!\n");
    return false;
  }
  ...
  return true;      
}

  /* in another function */
  ...
  do {
    ...
    /* read password here */
    ...
  } while(!password_is_safe(password));

It makes it much easier to understand the logic of the program without scrolling up and down.

Edit3:

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

#define STRINGIFY(x) #x
#define STRINGIFY_VALUE(x) STRINGIFY(x)

#define MAX 80

static bool test_and_complain(const bool test, const char *complain)
{
    if (test) {
        printf("%s\n", complain);
    }
    return test;
}

static void write_history(const char *password)
{
    FILE *f = fopen("passHistory.txt", "w");
    // always check if fopen() was successful
    if (!f) {
        fprintf(stderr, "can't write password history\n");
        exit(EXIT_FAILURE);
    }
    fprintf(f, "%s\n", password);
    fclose(f);
}

void validatePass()
{
    char password[MAX+1];
    int iUpper,iLower,iSymbol,iNumber,iTotal;

    //shows user password guidelines
    printf("\n\n\t\tPassword rules: ");
    printf("1. Passwords must be at least 9 characters long and less than 15 characters.");
    printf("2. Passwords must have at least 2 numbers in them.");
    printf("3. Passwords must have at least 2 uppercase letters and 2 lowercase letters in them.");
    printf("4. Passwords must have at least 1 symbol in them (eg ?, $, £, %%).");
    printf("5. Passwords may not have small, common words in them eg hat, pow or ate.");

    // loop until we got a good password
    bool pw_invalid;
    do {
        //gets user password input
        printf("Enter your password following password rules: ");
        // Security risc:
        // Never ever use "%s" without specifying a length!
        // scanf("%s", password);
        scanf("%" STRINGIFY_VALUE(MAX) "s", password);

        countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);

        // Notice that you could eliminate the boolean variable and
        // wrap all the tests in a single expression and put
        // that inside the loop condition of the loop.
        // I think it looks nicer this way though.
        // Notice that the || operator does not evaluate the right hand
        // expression if the left hand expression evaluates to true.
        // I.e. after the first test fails, no other tests are performed.
        // This is equivalent to the if-else cascade from before.
        pw_invalid = false;
        pw_invalid = pw_invalid || test_and_complain(
                      (iUpper < 2),
                      "Not enough uppercase letters!!!");
        pw_invalid = pw_invalid || test_and_complain(
                      (iLower < 2),
                      "Not enough lowercase letters!!!");
        pw_invalid = pw_invalid || test_and_complain(
                      (iSymbol < 1),
                      "Not enough symbols!!!");
        pw_invalid = pw_invalid || test_and_complain(
                      (iNumber < 2),
                      "Not enough numbers!!!") ;
        pw_invalid = pw_invalid || test_and_complain(
                      (iTotal < 9),
                      "Not enough characters!!!");
        pw_invalid = pw_invalid || test_and_complain(
                      (checkWordInFile("dictionary.txt",password)==gC_FOUND),
                      "Found your word in the dictionary");
        pw_invalid = pw_invalid || test_and_complain(
                      (checkWordInFile("passHistory.txt",password)==gC_FOUND),
                      "You already used this password recently");
    } while(pw_invalid);

    printf("\nYour new password is verified\n");
    // Security risc:
    // Never ever use a user supplied string as a format string!
    // printf(password);
    printf("%s\n", password);

    //writing password to passHistroy file.
    write_history(password);

    printf("\n\n\n");
    system("pause");
} //end validatePass method

If this was homework, please check back with your grade. 😉