Question

I am using Linux and there is a custom function of which returns an ASCII int of current key sort of like getch(). When trying to get used to it and how to store the password I came into an issue, my code is as follows:

int main() {
    int c;
    char pass[20] = "";

    printf("Enter password: ");
    while(c != (int)'\n') {
        c = mygetch();
        strcat(pass, (char)c);
        printf("*");
    }

    printf("\nPass: %s\n", pass);

    return 0;
}

Unfortunately I get the warning from GCC:

pass.c:26: warning: passing argument 2 of ‘strcat’ makes pointer from integer without a cast
/usr/include/string.h:136: note: expected ‘const char * __restrict__’ but argument is of type ‘char’

I tried using pointers instead of a char array for pass, but the second I type a letter it segfaults. The function works on its own but not in the loop, atleast not like getch() would on a Windows system.

What can you see is wrong with my example? I am enjoying learning this.

EDIT: Thanks to the answers I came up with the following silly code:

int c;
int i = 0;
char pass[PASS_SIZE] = "";

printf("Enter password: ");
while(c != LINEFEED && strlen(pass) != (PASS_SIZE - 1)) {
    c = mygetch();
    if(c == BACKSPACE) {
        //ensure cannot backspace past prompt
        if(i != 0) {
            //simulate backspace by replacing with space
            printf("\b \b");
            //get rid of last character
            pass[i-1] = 0; i--;
        }
    } else {
        //passed a character
        pass[i] = (char)c; i++;
        printf("*");
    }
}
pass[i] = '\0';
printf("\nPass: %s\n", pass);

Answer 1

The problem is that strcat expects a char * as its second argument (it concatenates two strings). You don’t have two strings, you have one string and one char.

If you want to add c to the end of pass, just keep an int i that stores the current size of pass and then do something like

pass[i] = (char) c.

Make sure to null-terminate pass when you are done (by setting the last position to 0).