[Programming] scanf()

Issue: scanf() by char or string goes wrong result.

#include <stdio.h>

int main(int argc, char **argv)
{
        int valA;
        char valB;

        scanf ("%d", &valA);
        printf ("valA=%d\n", valA);
        scanf ("%c", &valB);
        printf ("valB=%c\n", valB);

        return 0;
}

Result:

3
valA=3
valB=


Expect result:

3

valA=3

4

valB=4

Reason: scanf() doesn't handle new line character, "\n".

Solution1: Discard the last character "\n" by "%*c".


#include <stdio.h>

int main(int argc, char **argv)
{
        int valA;
        char valB;

        scanf ("%d%*c", &valA);
        printf ("valA=%d\n", valA);
        scanf ("%c%*c", &valB);
        printf ("valB=%c\n", valB);

        return 0;
}


Solution2: Add a space character to second scanf().

#include <stdio.h>

int main(int argc, char **argv)

{

        int valA;

        char valB;

        scanf ("%d", &valA);

        printf ("valA=%d\n", valA);

        scanf (" %c", &valB); // It is " %c". There is a space character in front of %c.

        printf ("valB=%c\n", valB);

        return 0;

}

Solution3: Read out the "\n" by getchar();

#include <stdio.h>

int main(int argc, char **argv)
{
        int valA;
        char valB;

        scanf ("%d", &valA);
        getchar();
        printf ("valA=%d\n", valA);

        scanf ("%c", &valB);
        getchar();
        printf ("valB=%c\n", valB);

        return 0;
}