How to store formatted data to array in C?

Question

I have this code to substring the array src into 4 characters and save each substring into char dest[5]; array. It works fine. Now, I want to store every 4 characters into another format - unsigned int- %u in another array unsigned long k[4] ; I've been trying to store the formatted input in k using sprintf(), but it does not giving me the conversion of each element in array dest. So, I could have k[0] = dest[0], k[1]= dest[1], and so on!

        unsigned int k [4];
        char dest[5] ; // 4 chars + terminator */
        char src [] = "123456789abcdefg"
        int len = strlen(src);
        int b = 0;
        int bb=1;
        while (b*4 < len) {
            strncpy(dest, src+(b*4), 4);

            printf("loop %s\n",dest);

           sprintf(&k, "%u",dest);
            puts(k);                
            b++;

        }

I just got the solution,

unsigned long *k = (unsigned long *) dest;

Anyways, Thank you guys!!

I think an nested loop could help for (i=0;i <5;i++) k [i]=dest [i]; — kabab
– kabab, Commented Mar 20, 2015 at 17:37

user3469811 · Accepted Answer · 2015-03-20 17:31:26Z

1

sprintf() and puts() expect pointer to chars, k is a pointer to unsigned int array. proper casts should solve your problem

answered Mar 20, 2015 at 17:31

user3469811

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Comments

R Sahu · Accepted Answer · 2015-03-20 17:34:15Z

1

You have a few errors. Here are my suggestions to fix them.

while (b*4 < len) {
    strncpy(dest, src+(b*4), 4);
    dest[4] = '\0';    // Make sure to null terminate dest

    printf("loop %s\n",dest);

    // Need sscanf, not sprintf
    // sprintf(&k, "%u",dest); 
    sscanf(dest, "%u", &k[b] );

    // Need printf, not puts, 
    // puts(k);
    printf("%u", k[b]);

    b++;

}

answered Mar 20, 2015 at 17:34

R Sahu

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2 Comments

AliDeV Over a year ago

it is returning 0 values in every k elements.

R Sahu Over a year ago

I can see how you would get 0 in k[3] -- can't convert "defg" to a number but that shouldn't be the case for the other elements of k. See working code at ideone.com/AnZofC.

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