Copy char input into array of strings

Question

I'm currently refreshing my C skills and having trouble with the following code:

int main (int argc, const char * argv[]) {

    @autoreleasepool {

        int numberOfTestCases;

        scanf("%d", &numberOfTestCases);

        char *a[numberOfTestCases];

        for (int i = 0; i < numberOfTestCases; i++) {

            char input[100];
            scanf("%s", input);
            a[i] = input;
        }

        for (int k = 0; k < numberOfTestCases; k++) {
            printf("%s\n", a[k]);
        }

    }
    return 0;
}

First I want to enter the user a number to determine how many strings she/he wants to enter.

Second I want to let the user enter the number of strings and store them in an array of strings.

Last I want to loop over that array and print out all the values. So my test input is e.g. something like:

5

My

name

is

John

Doe

with an expected result of

My

name

is

John

Doe

Instead the result is:

Doe

I can't figure out how to insert the input in the array.. very thankful for a hint in the right direction.

That is not a C program, neither is it C++. Possibly Objective-C. — Some programmer dude
– Some programmer dude, Commented Feb 4, 2015 at 13:08
Your title mentions NSStringWithFormat, which is Objective-C, but your code or question body don't even seem relevant to the title. — crashmstr
– crashmstr, Commented Feb 4, 2015 at 13:09
Oh, and a[i] = input; will make each array element point to the same char input[100]; which also goes out of scope outside the for loop. — crashmstr
– crashmstr, Commented Feb 4, 2015 at 13:12
Sorry for the wrong title. That was an old browser cache error. — MrBr
– MrBr, Commented Feb 4, 2015 at 13:15

Some programmer dude · Accepted Answer · 2015-02-04 13:12:16Z

3

If that was a C program, you would have undefined behavior because you have an array of pointers, and each pointer you make point to a variable inside a nested scope, which means that variable will be out of scope outside of the loop, and the pointers (who are all pointing to the same memory) will be stray leading to said undefined behavior.

answered Feb 4, 2015 at 13:12

Some programmer dude

411k36 gold badges420 silver badges655 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

crashmstr Over a year ago

I would guess that it would be undefined behavior in Objective-C as well.

Collectives™ on Stack Overflow

Copy char input into array of strings

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related