Question

Im trying to store some user-input names in a ragged array. However i get an error during run-time and im trying to figure out what has gone wrong.

My code:

int num, count, i;
char *myNames[10];

printf("Enter the number of names: ");
scanf( "%d" , &num);

fflush(stdin);

    // Ask user to input the name
for( count = 0 ; count <= num ; count++)
{
    printf("Enter a name: ");
    scanf( "%s" , myNames[count]);
    fflush(stdin);
}

    // To check if names are stored correctly
printf("%s", *myNames[1]);

return 0;
}

Grateful if anyone can share some help, or at least point me in the right direction. Thanks

Answer 1

You need to allocate space for the strings themselves; currently you only allocate an array of 10 pointers, but they never actually point to any valid memory; hence the error that you get when scanf() tries to write into them.

Of course, in order to allocate the right amount of space for a string you need to know how many characters are in the string, which is a bit of a chicken-and-egg problem; you should probably use one stack-allocated array to let scanf() write into and then strdup() that, like this:

for( count = 0 ; count <= num ; count++)
{
   printf("Enter a name: ");
   char temp[1024];
   scanf( "%s" , temp);
   myNames[i] = strdup(temp);
   fflush(stdin);
}

… and of course if you wanted your program to be 100% correct and avoid a memory leak, you’d need to free() each of the 10 strings before returning, but if this is just a toy program you can ignore that and just let the OS deal with cleaning up.