User input?

This is a discussion on User input? within the C Programming forums, part of the General Programming Boards category; I am new to programming in C but doing fairly well, I have created a structure and a doubly linked ...

  1. #1
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    User input?

    I am new to programming in C but doing fairly well, I have created a structure and a doubly linked list, I think, and can get it to work. My problem seams to be in collecting the users input. I can use scanf to take in the data, but I donít like the way it returns the curser to the next line to get the input, and have a problem taking in a string. I am using an array, but as you know with scanf it only reads to the first space. I have tried gets and because I am entering the info into a structure it gives me an error, some type of type conflict. I have thought of using gets to a pointer, but when I save my info will it only save the pointer or the info? Anyway I would be grateful for some ideas.

  2. #2
    ATH0 quzah's Avatar
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    Using fgets( ) requires a buffer to read into. The same goes for it's "less safe" brother, 'gets'. Post a sample attempt, and we'll give you a hand.

    For example:

    char buf[256]={0};

    fgets( buf, 256, stdin );

    This will read into 'buf', a maximum of 255 characters, from the standard input device (keyboard).

    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
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    Question

    Here is a copy of the code I have written to this point. I think the pointers and links work properly, if you see a problem with it let me know. Otherwise the problem I am having is with the user inputting the street address. Pleas help.

    struct account {
    int custID;
    char lastname[25];
    char firstname[25];
    char street[50];
    struct account *next;
    struct account *prior;
    };
    struct account *first,*current,*newptr;

    int idnum = 0;

    void addNewAccount(void)
    {
    char buffer[64];
    char *last;

    newptr = (struct account *)malloc(sizeof(struct account));

    if(first==(struct account *)NULL)
    {
    first = current = newptr;
    current->prior = NULL;
    }

    else
    {
    current = first;

    while(current->next != (struct account *)NULL)
    current = current->next;

    last = current;
    current->next = newptr;
    current = newptr;
    current->prior = last;
    }

    idnum++;
    printf("Cust ID:\n %i\n\n",idnum);
    current->custID = idnum;

    puts("Enter customer's last name: ");
    scanf(" %s", current->lastname);

    puts("\n");

    puts("Enter customer's first name: ");
    scanf(" %s", current->firstname);

    puts("\n");

    puts("Enter customer's street address: ");
    /*scanf(" %s", current->street);*/

    puts("\n");

    system("pause");

    current->next = (struct account *)NULL;

    }

  4. #4
    ATH0 quzah's Avatar
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    Similar to above, you should try modifying the input to use 'fscanf' to ensure that your user doesn't intentionally break your program. For example, for "lastname" I could enter:

    33333333333333333333333333333333333333333333333333 33333333333333333333333333333333333333333333333333 33333333333333333333333333333333333333333333333333 33333333333333333333333333333333333333333333333333 33333333

    and your program would puke.

    Additionally, with fgets(), you'll not have to worry about it stopping on a space.

    scanf( "%[^\n]", current->street );

    That should work too. I think.

    Quzah.
    Hope is the first step on the road to disappointment.

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