Print from array of strings in C

Question

I have written the following program:

char name[100], firstDigits[13], cards[5000][16];

srand(1019336);
int i, j;
char c = '0';
for(i=0;i<13;i++){
    c = '0' + (rand() % 43);
    while(c > 57 && c < 65){
        c = '0' + (rand() % 43);
    }
    firstDigits[i] = c;

}
printf("%s \n", firstDigits);
for(i=0;i<5;i++){
    for(j=0;j<13;j++){
        cards[i][j] = firstDigits[j];
    }
}
for(i=0;i<5;i++){

    for(j=13;j<16;j++){
        c = '0' + (rand() % 43);
        while(c > 57 && c < 65){
            c = '0' + (rand() % 43);
        }
        cards[i][j] = c;
    }
}

printf("%s \n", cards[1]);

The first loop generates a string of 13 characters which are from 0-9 and A-Z. Then I want to generate an array of 5000 strings where each string's first 13 'letters' are that of firstDigits[13]. The problem is that when I try to print one of those strings like above I get as output all of the strings in the array! Why is this happening?

There are at least a few errors there. I am unsure of what exactly you are trying to do, though. — Evan Carslake
– Evan Carslake, Commented Apr 13, 2017 at 0:25

Richard · Accepted Answer · 2017-04-13 00:31:51Z

2

C strings must be null terminated. Printf will output chars until it hits a null. After you finish generating your random string add '\0' to the end. Of course you'll have to increase you array size by 1 to accommodate it.

answered Apr 13, 2017 at 0:31

Richard

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Comments

David Schwartz · Accepted Answer · 2017-04-13 00:30:45Z

2

The %s format specifier is only for strings. It's not for arrays of characters. How would it know how many characters to print?

You can use %.13s to print 13 characters.

edited Apr 13, 2017 at 0:30

answered Apr 13, 2017 at 0:25

David Schwartz

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3 Comments

Shivalnu Over a year ago

Does that mean that the array of strings is correctly generated and I just had a mistake in printf?

David Schwartz Over a year ago

@Peter I can't tell. The output bug is blocking the ability to tell if the generated array is correct. Fix it and keep going.

aschepler Over a year ago

Do you mean "%.13s"?

Nguai al · Accepted Answer · 2017-04-13 03:04:52Z

0

Since there are 16 characters for each outer index (char [][16]), you can use an array to print each character:

for(j=0;j<16;j++)
    printf("%c", cards[1][j]);

In this case, this prints every character of the outer index 1.

answered Apr 13, 2017 at 3:04

Nguai al

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