I copied your code into a blank project and compiled... no errors... that's good. I ran it and the program immediately crashed... not good.
I put in some debug statements sprinkled here and there in the main and read_from_file functions. That would be a handy skill for you to develop by the way. I discovered that the fclose on a non-existant file (first time program is run there is no file) was causing the crash on my system. So I added the check mentioned below towards the very end of the read_from_file function so we only call fclose if we read in some data.
That isn't the only problem of course. Once I made the above changes, I was able to add airlines, delete airlines and exit the program. I was then able to successfully restart the program and display the list of airlines that had been saved and read from the file. At this point I hadn't entered any flight or passenger information for any of the airlines. I added a flight to one of the airlines I exited the program and started the program again. Now when I displayed the list of airlines, the airline list was messed up. Attempting to exit the program at this point also seemed to be a little problematic. So, there seems to be an issue with either saving or reading from the file once you get to the point where you start reading/writing flight information.Code:airline * read_from_file() { FILE *fp; airline *start, *curr, *temp; int length = 0; int airline_count= 0; int flight_count = 0; int passenger_count = 0; // Initialize pointers start = curr = NULL; // Open file for reading fp = fopen("airline.txt","rb"); // Not necessary while(!feof(fp)) { // Read in number of airlines stored in file if( fp == NULL) airline_count = 0; else fread(&airline_count,sizeof(int),1,fp); // Loop through "airline_count" airlines for( ; airline_count > 0; --airline_count ) { // allocate room for a single airline structure and flight link to NULL temp = (airline *)malloc(sizeof(airline)); temp->next = NULL; temp->node1 = NULL; // read airline name length fread(&length,sizeof(int),1,fp); //allocate sufficent memory for the airline name temp->airlinename = (char *)malloc(length+1); // read in airline's name and NULL terminate fread(temp->airlinename,length,1,fp); temp->airlinename[length] = 0; // Add current airline to end of growing list of airlines if( start == NULL ) { start = curr = temp; } else { curr->next = temp; curr = curr->next; } // Read in number of flights stored for the airline in file fread(&flight_count,sizeof(int),1,fp); // Loop through "flight_count" flight for( ; flight_count > 0; --flight_count ) { // allocate room for a single flight structure and set passenger link to NULL curr->node1 = (flight *)malloc(sizeof(flight)); curr->node1->next = NULL; curr->node1->node2 = NULL; // read flight name length fread(&length,sizeof(int),1,fp); //allocate sufficent memory for the flight name curr->node1->flightname = (char *)malloc(length+1); // read in flight name and NULL terminate fread(curr->node1->flightname,length,1,fp); curr->node1->flightname[length] = 0; // read departure location length fread(&length,sizeof(int),1,fp); //allocate sufficent memory for the departure location curr->node1->departure_location = (char *)malloc(length+1); // read in departure location and NULL terminate fread(curr->node1->departure_location,length,1,fp); curr->node1->departure_location[length] = 0; // read arrival location length fread(&length,sizeof(int),1,fp); //allocate sufficent memory for the arrival location curr->node1->arrival_location = (char *)malloc(length+1); // read in arrival location and NULL terminate fread(curr->node1->arrival_location,length,1,fp); curr->node1->arrival_location[length] = 0; // read take off time length fread(&length,sizeof(int),1,fp); //allocate sufficent memory for the take off time curr->node1->take_off_time = (char *)malloc(length+1); // read in take off time and NULL terminate fread(curr->node1->take_off_time,length,1,fp); curr->node1->take_off_time[length] = 0; // Add current flight to end of growing list of flights if( start->node1 == NULL ) { start->node1 = curr->node1 = temp->node1; } else { curr->node1->next = temp->node1; curr->node1 = curr->node1->next; } // Read in number of passengers stored for that file fread(&passenger_count,sizeof(int),1,fp); // Loop through "passenger_count" passengers for this flight for( ; passenger_count > 0; --passenger_count ) { // allocate room for a single passenger structure curr->node1->node2 = (passenger *)malloc(sizeof(passenger)); curr->node1->node2->next = NULL; // read passenger name length fread(&length,sizeof(int),1,fp); //allocate sufficent memory for the passenger name curr->node1->node2->name = (char *)malloc(length+1); // read in passenger name and NULL terminate fread(curr->node1->node2->name,length,1,fp); curr->node1->node2->name[length] = 0; // Add current passenger to end of growing list of // passengers for this flight if( start->node1->node2 == NULL ) { start->node1->node2 = curr->node1->node2 = temp->node1->node2; } else { curr->node1->node2->next = temp->node1->node2; curr->node1->node2 = curr->node1->node2->next; } } } } } // Not necessary // Should only have to close file if there was a file to read if( airline_count > 0 ) fclose(fp); return start; }
Another problem is all your menu functions seem to recursively calling themselves. This could eventually come back to bite you and should be fixed. As an example:
This function should be rewritten to look something like:Code:// Menu Function which is handles the airlinelist airline* airline_menu(airline *start) { int choice; printf("Welcome to the Main Menu\n"); printf("Please enter your choice from the menu shown below\n"); printf("1: Add a new airline to this airport\n"); printf("2: Delete an airline from the airport\n"); printf("3: Display the Airlines List at this Airport\n"); printf("4: Enter Flight menu for an airline\n"); printf("5: Exit the program\n"); scanf ("%d", &choice); switch(choice) { case 1: { start1 = create_airline_node(start1); } break; case 2: { start1 = delete_airline_node(start1); } break; case 3: { print_airline_list(start1); } break; case 4: { start1 = enter_flight_menu(start1); } break; case 5: { write_to_file(start1); exit(1); } break; default: { start1 = airline_menu(start1); } break; } printf("\n"); start1 = airline_menu(start1); return start1; }
There, no more recursion. However, I must point out that you are passing in a start pointer but everywhere in the code above you are using the global start1 pointer.Code:airline* airline_menu(airline *start) { int choice; do { printf("Welcome to the Main Menu\n"); printf("Please enter your choice from the menu shown below\n"); printf("1: Add a new airline to this airport\n"); printf("2: Delete an airline from the airport\n"); printf("3: Display the Airlines List at this Airport\n"); printf("4: Enter Flight menu for an airline\n"); printf("5: Exit the program\n"); scanf ("%d", &choice); switch(choice) { case 1: start1 = create_airline_node(start1); break; case 2: start1 = delete_airline_node(start1); break; case 3: print_airline_list(start1); break; case 4: start1 = enter_flight_menu(start1); break; case 5: write_to_file(start1); break; default: break; } printf("\n"); } while( choice != 5 ); return start1; }
It would also seem that you need to have a function that cleans up all the allocated memory for your linked lists. Something that gets called before main exits.
Make the changes I made above and try to get a little bit further. Put in temporary printf statements to help debug your code. If you still have problems, post you code again and explain what part of your code you think isn't working correctly.
