Question

This is a very fun problem I am running into. I did a lot of searching on stack overflow and found others had some similar problems. So I wrote my code accordingly. I originally had fscan() and strcmp(), but that completely bombed on me. So other posts suggested fgets() and strncmp() and using the length to compare them.

I tried to debug what I was doing by printing out the size of my two strings. I thought, maybe they have /n floating in there or something and messing it up (another post talked about that, but I don’t think that is happening here). So if the size is the same, the limit for strncmp() should be the same. Right? Just to make sure they are supposedly being compared right. Now, I know that if the strings are the same, it returns 0 otherwise a negative with strncmp(). But it’s not working.

Here is the output I am getting:

perk
repk
Enter your guess: perk
Word size: 8 and Guess size: 8
Your guess is wrong
Enter your guess: 

Here is my code:

void guess(char *word, char *jumbleWord)
{
        size_t wordLen = strlen(word);
        size_t guessLen; 
        printf("word is: %s\n",word);
        printf("jumble is: %s\n", jumbleWord);


        char *guess = malloc(sizeof(char) * (MAX_WORD_LENGTH + 1));
        do
        {
            printf("Enter your guess: ");
            fgets(guess, MAX_WORD_LENGTH, stdin);
            printf("\nword: -%s- and guess: -%s-", word, guess); 
            guessLen = strlen(guess);
            //int size1 = strlen(word);
            //int size2 = strlen(guess); 

            //printf("Word size: %d and Guess size: %d\n",size1,size2);


            if(strncmp(guess,word,wordLen) == 0)
            {
                printf("Your guess is correct\n"); 
                break; 
            }

            }while(1);
    }

I updated it from suggestions below. Especially after learning the difference between char * as a pointer and referring to something as a string. However, it’s still giving me the same error.

Please note that MAX_WORD_LENGTH is a define statement used at the top of my program as

#define MAX_WORD_LENGTH 25

Answer 1

sizeof(guess) is returning the size of a char * not the length of the string guess. Your problem is that you’re using sizeof to manage string lengths. C has a function for string length: strlen.

sizeof is used to determine the size of data types and arrays. sizeof only works for strings in one very specific case – I won’t go into that here – but even then, always use strlen to work with string lengths.

You’ll want to decide how many characters you’ll allow for your words. This is a property of your game, i.e. words in the game are never more that 11 characters long.

So:

// define this somewhere, a header, or near top of your file
#define MAX_WORD_LENGTH 11

// ...

size_t wordlen = strlen(word);
size_t guessLen;

// MAX_WORD_LENGTH + 1, 1 more for the null-terminator:
char *guess = malloc(sizeof(char) * (MAX_WORD_LENGTH + 1));

printf("Enter your guess: ");
fgets(guess, MAX_WORD_LENGTH, stdin);

guessLen = strlen(guess);

Also review the docs for fgets and note that the newline character is retained in the input, so you’ll need to account for that if you want to compare the two words. One quick fix for this is to only compare up to the length of word, and not the length of guess, so: if( strncmp(guess, word, wordLen) == 0). The problem with this quick fix is that it will pass invalid inputs, i.e. if word is eject, and guess is ejection, the comparison will pass.

Finally, there’s no reason to allocate memory for a new guess in each iteration of the loop, just use the string that you’ve already allocated. You could change your function setup to:

char guess(char *word, char *jumbledWord)
{
    int exit;

    size_t wordLen = strlen(word);
    size_t guessLen; 

    char *guess = malloc(sizeof(char) * (MAX_WORD_LENGTH + 1));

    do
    {
        printf("Enter your guess: ");
        // ...