Break out of this while loop

Question

I'm reading in from a text file likewise:

George Washington, 2345678
John Adams, 3456789
Thomas Jefferson, 4567890
James Madison, 0987654
James Monroe, 9876543
John Quincy Adams, 8765432
Andrew Jackson, 7654321
Martin Van Buren, 6543210
William Henry Harrison, 5432109
John Tyler, 4321098

The function to delete the name works, however when it is successful the printf statements just continue to loop in the command window. I tried using a break statement at the end of the loop, however that only led to saying that the name wasn't found. Can someone offer any insight?

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//Creates node for holding student's information
struct node
{
    char name [50];
    int id;
    struct node *next;
}*head;

//Create Function Prototypes
void readDataFile ();
void insert(char *inName, char *inID);
void display(struct node *d);
int deleteID(int num);
void deleteName(char *delete_name);


//Main function
int main()
{
    //Declare variables
    int i, num, delete_id, id;
    char *name;
    char nameDelete [50];
    char nameInsert [50];
    struct node *n;

    //initialize link list
    head = NULL;

    //Read in file
    readDataFile();

    //Create list of operations utilized in program
    while (1)
    {
        printf("\nList Operations\n");
        printf("===============\n");
        printf("1.Insert\n");
        printf("2.Display\n");
        printf("3.Delete by ID\n");
        printf("4.Delete by Name\n");
        printf("5.Exit\n");
        printf("Enter your choice : ");

        if(scanf("%d", &i) <= 0)
        {
            printf("Enter only an Integer\n");
            exit(0);
        }
        else
        {
            switch(i)
            {
                case 1:
                    getchar();
                    printf("Enter the name to insert:");
                    scanf("%[^\n]s", nameInsert);
                    printf("\nEnter the ID associated with the name: ");
                    scanf("%d", &id);
                    break;
                case 2:
                    if (head == NULL)
                        printf("List is Empty\n");
                    else
                    {
                        printf("Elements in the list are:\n");
                    }
                    display(n);
                    break;
                case 3:
                    if(head == NULL)
                        printf("List is Empty\n");
                    else
                    {
                        printf("Enter the ID number to delete: ");
                        scanf("%d", &delete_id);
                    }

                    if(deleteID(delete_id))
                        printf("%d deleted successfully \n", delete_id);
                    else
                        printf("%d not found in the list\n", delete_id);
                    break;
                case 4:
                    getchar();
                    if(head == NULL)
                        printf("List is Empty\n");
                    else
                    {
                        printf("Enter name to delete: ");
                        scanf("%[^\n]s", nameDelete);
                        printf("Checking for name %s...\n", nameDelete);
                        printf("%s not found in the list\n", nameDelete);
                        deleteName(nameDelete);
                    }
                    break;
                case 5:
                    return 0;
                default:
                    printf("Invalid option\n");
            }
        }
    }
    return 0;
}

//Define the functions
//Function to delete by name
void deleteName(char *delete_name)
{
    //Create temporary and helper node
    struct node *temp, *helper;

    //Set temp equal to head
    temp = head;

    //Loop until the end of the list
    while(temp != NULL)
    {
        if(strcmp(temp->name, delete_name) == 0)
        {
            if(temp == head)
            {
                head = temp->next;
                free(temp);
                printf("Found %s!\n", delete_name);
                printf("%s deleted successfully\n", delete_name);
            }
            else
            {
                helper->next = temp->next;
                free(temp);
                printf("Found %s!\n", delete_name);
                printf("%s deleted successfully\n", delete_name);
            }
        }
        else
        {
            helper = temp;
            temp = temp->next;
        }
    }
break;
}

Answer 1

Please learn how to make an MCVE ( How to create a Minimal, Complete, and Verifiable Example? ) or SSCCE ( Short, Self-Contained, Correct Example ) — two names and links for the same basic idea.

Here's an MCVE derived from your code. I added the missing break; or return; from the loop in deleteName() . I rewrote main() essentially completely, but it works cleanly:

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct node
{
    char name[50];
    int id;
    struct node *next;
} *head;

void deleteName(char *delete_name);

int main(void)
{
    struct node *n;

    head = NULL;

    head = malloc(sizeof(*head));
    assert(head != 0);
    strcpy(head->name, "Abraham Lincoln");
    head->id = 1;
    head->next = 0;

    n = malloc(sizeof(*n));
    strcpy(n->name, "George Washington");
    n->id = 2;
    n->next = head;
    head = n;

    n = malloc(sizeof(*n));
    strcpy(n->name, "John Adams");
    n->id = 3;
    n->next = head;
    head = n;

    deleteName("George Washington");
    deleteName("John Adams");
    deleteName("Abraham Lincoln");

    return 0;
}

void deleteName(char *delete_name)
{
    struct node *temp, *helper = 0;

    temp = head;

    while (temp != NULL)
    {
        if (strcmp(temp->name, delete_name) == 0)
        {
            if (temp == head)
            {
                head = temp->next;
                free(temp);
                printf("Found %s!\n", delete_name);
                printf("%s deleted successfully\n", delete_name);
            }
            else
            {
                helper->next = temp->next;
                free(temp);
                printf("Found %s!\n", delete_name);
                printf("%s deleted successfully\n", delete_name);
            }
            return;  // The key change!
        }
        else
        {
            helper = temp;
            temp = temp->next;
        }
    }
}

This ran cleanly under valgrind and Mac OS X 10.10.2 with GCC 4.9.1.

Found George Washington!
George Washington deleted successfully
Found John Adams!
John Adams deleted successfully
Found Abraham Lincoln!
Abraham Lincoln deleted successfully

It is important to learn how to be brutal about stripping out irrelevant code when creating an MCVE.

Answer 2

The break keyword will break out of the nearest switch or loop. Therefore, you can try this:

while(temp != NULL)
{
    if(strcmp(temp->name, delete_name) == 0)
    {
        if(temp == head)
        {
            head = temp->next;
            free(temp);
            printf("Found %s!\n", delete_name);
            printf("%s deleted successfully\n", delete_name);
            break;
        }
        else
        {
            helper->next = temp->next;
            free(temp);
            printf("Found %s!\n", delete_name);
            printf("%s deleted successfully\n", delete_name);
            break;
        }
    }
    else
    {
        helper = temp;
        temp = temp->next;
    }
}

An alternate solution is to set temp to NULL after you free it (this is good practice anyway, so that might be another idea)

Answer 3

Add the return statement at the end of the if block once you have found the name to be deleted

void deleteName(char *delete_name)
{
    //Create temporary and helper node
    struct node *temp, *helper;

    //Set temp equal to head
    temp = head;

    //Loop until the end of the list
    while(temp != NULL)
    {
        if(strcmp(temp->name, delete_name) == 0)
        {
            if(temp == head)
            {
                head = temp->next;
                free(temp);
                printf("Found %s!\n", delete_name);
                printf("%s deleted successfully\n", delete_name);
            }
            else
            {
                helper->next = temp->next;
                free(temp);
                printf("Found %s!\n", delete_name);
                printf("%s deleted successfully\n", delete_name);
            }
            return; 
        }
        else
        {
            helper = temp;
            temp = temp->next;
        }
    }
}

Also you how are planning to indicate that the name isn't part of the list, as opposed to being found and deleted. You can change modify the function such that it returns an error code when it hasn't found the name in the list, which is then used to indicate the name was never in the list to begin with.

Answer 4

I did not really look at the delete() function,
however, the following code illustrates how the 
code should be formatted, etc.

notice the checking for input errors, which should always be performed
notice the separation of the struct definition from the struct declaration
notice the easy readability of the switch cases
    by incorporating some vertical white space
notice the simple comments after the closing braces
notice that no call to an action is performed if the linked list is empty



#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//define node for holding student's information
struct node
{
    char name [50];
    int id;
    struct node *next;
};

// create head pointer for linked list of student info
// and initialize
struct node *head = NULL;

// Function Prototypes
// note: if all these functions are only accessed within this file
//       then they should be declared with the 'static' modifier
void readDataFile (void);
void insert (char *inName, char *inID);
void display (struct node *d);
void deleteID (int delete_ID);
void deleteName (char *delete_name);


//Main function
int main()
{
    //Declare local variables
    // notice use of meaningful names
    // notice, for readability and documentation, 
    //         only one variable declared per line
    int i;  // receives user menu selection input
    int idDelete;
    int idInsert;
    char nameDelete [50];
    char nameInsert [50];
    // struct node *n; // unused variable
    int done = 0; // used to exit when user enters '5'



    //Read in file
    readDataFile();

    //Create list of operations utilized in program
    while (!done)
    {
        printf("\nList Operations\n");
        printf("===============\n");
        printf("1.Insert\n");
        printf("2.Display\n");
        printf("3.Delete by ID\n");
        printf("4.Delete by Name\n");
        printf("5.Exit\n");
        printf("Enter your choice : ");

        if( 1 != scanf("%d", &i) )
        { // then, scanf failed
            perror( "scanf for choice failed");
            exit( EXIT_FAILURE );
        }

        // implied else, scanf successful

        switch(i)
        {
            case 1:
                int ch;
                while(EOF != (ch = getchar()) && (ch != '\n'));

                printf("Enter the name to insert:");

                if( 1 != (scanf("%[^\n]s", nameInsert) ) )
                { // then scanf failed
                    perror( "scanf for new student name failed");
                    exit( EXIT_FAILURE );
                }

                // implied else, scanf successful

                printf("\nEnter the ID associated with the name: ");

                if( 1 != (scanf("%d", &idInsert) ) )
                { // then scanf failed
                    perror( "scanf for new student ID failed");
                    exit( EXIT_FAILURE );
                }

                // implied else, scanf successful

                insert( nameInsert, idInsert );
                break;

            case 2:
                if (head == NULL)
                    printf("List is Empty\n");
                else
                {
                    printf("Elements in the list are:\n");
                    display(n);
                } // end if
                break;

            case 3:
                if(head == NULL)
                    printf("List is Empty\n");
                else
                {
                    printf("Enter the ID number to delete: ");

                    if( 1 != (scanf("%d", &idDelete) ) )
                    { // then, scanf failed
                        perror( "scanf for ID to delete failed");
                        exit( EXIT_FAILURE );
                    } 

                    // implied else, scanf successful

                    deleteID(idDelete);
                } // end if
                break;

            case 4:
                int ch;
                while(EOF != (ch = getchar()) && (ch != '\n'));

                if(head == NULL)
                    printf("List is Empty\n");
                else
                {
                    printf("Enter name to delete: ");

                    if( 1 != (scanf("%[^\n]s", nameDelete) ) )
                    { // then, scanf failed
                        perror( "scanf for name to delete failed");
                        exit( EXIT_FAILURE );
                    }

                    // implied else, scanf successful

                    printf("Checking for name %s...\n", nameDelete);

                    deleteName(nameDelete);
                } // end if
                break;

            case 5:
                done = 1; // this will cause while() loop to exit
                break;

            default:
                printf("Invalid option\n");
                break;
        } // end switch
    } // end while
    return 0;
} // end of function: main