Thread: Why can I not enter the last while loop?

  1. #1
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    Why can I not enter the last while loop?

    /* The user is to enter a 9-digit social security number and check whether the number entered by the user is a valid SSN from a list of SSNs in a text file. */

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    
    int main()
    {
    int snn_num, user_ssn, ssn3, sum = 0;
        FILE * ssn;
        ssn = fopen("ssn_in.txt", "r");
     
        if (ssn == NULL ) {        // Checking if the file ssn_in.txt exists
        printf("The file ssn_in.txt does not exist\n");
        fclose(ssn);
        }
        
        else {
    printf("The Social Security Numbers are:\n");
        while (fscanf(ssn, "%d", &snn_num) != EOF) {
    sum = sum + 1;
    printf("%d\n",snn_num);
        } 
    }
     printf("Enter a 9-digit social security number: ");  // part 2
     scanf("%d", &user_ssn);
      
      
    
    
      
     if ((user_ssn <  100000000) || (user_ssn >= 1000000000)) // the input has to be  greater than and equal to 100000000 and less than 1000000000 or else exit program
         {
    printf("The number (%d) you entered is not a valid 9-digit social security number.\n", user_ssn);
         return 0;
    } 
      
    
    
      while (fscanf(ssn,"%d", &ssn3) != EOF) {   // if the input is within the range, the program will scan 
      
       if (user_ssn == ssn3 )
       printf("The SSN you entered (%d) is among the (%d) SSNs in the file ssn_in.txt", user_ssn, sum);
      
       else if (user_ssn != ssn3 )
       printf("The SSN you entered (%d) is NOT among the (%d) SSNs in the file ssn_in.txt", user_ssn, sum);
      }
      fclose(ssn);
    }

  2. #2
    Lurking whiteflags's Avatar
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    I think your biggest problem is that this loop generates so much output. For each number that doesn't match in the file it will say it's not okay, except for the one that matches. Just change where and how you report the results.

    Code:
    int user_ssn;
    int ssn3;
    int matchExists = 0;
    
    while (fscanf(ssn, "%d", &ssn3) != 1) {
       if (user_ssn == ssn3) {
          matchExists = 1;
          break;
       }
    }
    printf("The SSN you entered (%d) %s among the %d SSNs in the file\n", user_ssn, matchExists ? "is" : "is NOT", sum);
    Something like this works.
    Last edited by whiteflags; 01-27-2017 at 03:13 AM.

  3. #3
    and the hat of int overfl Salem's Avatar
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    Now is a good time to learn how to indent code.
    Indent style - Wikipedia

    > printf("The file ssn_in.txt does not exist\n");
    > fclose(ssn);
    If the file didn't open, there is nothing to close.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  4. #4
    Lurking whiteflags's Avatar
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    Also you might want to call rewind(ssn); before your last loop, if you're really going to read the file multiple times. You shouldn't need to do that, but whatever.
    Last edited by whiteflags; 01-27-2017 at 06:07 AM.

  5. #5
    Hurry Slowly vart's Avatar
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    Quote Originally Posted by whiteflags View Post
    Code:
    while (fscanf(ssn, "%d", &ssn3) != 1) {
    ...
    }
    Something like this works.
    You mean == 1 ?
    Otherwise I do not see how it could work
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

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