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POOptional parameters in fscanf [C]
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copied!<p>Hello I am struggling with creating my menu for my linked list. I am told to use fscanf to take in input, but I have an argument that the user may not always enter, specifically a number to add to the linked list. The way I have fscanf set up is it reads a char, a number, and then another char (the [enter] key). E.g. the user enters "a 20[enter]" to add the number 20 to the linked list. However, if the user enters "d[enter]", then the num field is invalid because the user entered a char! Note I <strong>cannot</strong> use fgets(). </p> <p>Do I need another fscanf field? Here's my menu code below:</p> <pre><code>int main(void) { struct node* head = NULL; int num, ret; char select = 'n'; char c; while (select != 'e') { printf("Enter:\na(dd) (x) = add a new node with value x to the list at the front of the list\n"); printf("d(el) = delete the first node of list\n"); printf("l(ength) = print the number of nodes in the list\n"); printf("p(rint) = print the complete list\n"); printf("z(ero) = delete the entire list\n"); printf("e(xit) = quit the program\n"); ret = (fscanf(stdin, "%c %d%c", &select, &num, &c)); if (ret == 3 && select == 'a' && c == '\n') Add(&head, num); else if (ret == 2 && select == 'd') Delete(&head); else if (ret == 2 && select == 'l') Length(head); else if (ret == 2 && select == 'p') PrintList(head); else if (ret == 2 && select == 'z' ) ZeroList(&head); else printf("invalid\n"); } return EXIT_SUCCESS; } </code></pre>

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