While loop does not terminate despite condition not fulfilled with scanf

Asked Sep 29 '20 at 09:35

Active Sep 29 '20 at 09:38

Viewed 30 times

I have a very simple 9 line program:

# include <stdio.h>

void main() {
    char input[20];
    scanf("%s20", input);

    while (input != "stop") {
      printf("%s\n", input);
      scanf("%s20", input);
    }
}

I am first reading a string from the user and then echoing it back. This works fine. However when the program receives the string "stop" i would expect the while-loop to terminate. It does not and I have to stop the loop with Ctr+C. Why is that?

edited Sep 29 '20 at 09:38

Konrad Rudolph

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asked Sep 29 '20 at 09:35

PixelRayn

1

`while (input != "stop")` ==> `while (strcmp(input, "stop"))` – pmg Sep 29 '20 at 09:36
1

`scanf("%s20", input);` ==> `scanf("%19s", input);` ==> `if (scanf("%19s", input) != 1) exit(EXIT_FAILURE);` – pmg Sep 29 '20 at 09:37
1

`void main()` ==> `int main()` ==> `int main(void)` – pmg Sep 29 '20 at 09:39

While loop does not terminate despite condition not fulfilled with scanf

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