I have got this program, inventory2.c, which allows a user to store a database of parts. It uses command-line switches to determine what course of action to take. I'm trying to add a command-line switch ' e ' which will allow you to erase a part from the database. I Insert a part, Part Number: 1, Name: Wrench, Quantity: 2, then i search for that part, it does what its suppose to, then i try to erase it. After i do my erase function, i use the s switch to search for it and the part isnt found, But when i use the insert switch again and enter part number 1, it says it already exists. Any help? Im stumped on what I need to do.
Code:/********************************************************* * From C PROGRAMMING: A MODERN APPROACH, Second Edition * * By K. N. King * * Copyright (c) 2008, 1996 W. W. Norton & Company, Inc. * * All rights reserved. * * This program may be freely distributed for class use, * * provided that this copyright notice is retained. * *********************************************************/ /* inventory2.c (Chapter 17, page 434) */ /* Maintains a parts database (linked list version) */ #include <stdio.h> #include <stdlib.h> #include "readline.h" #define NAME_LEN 25 struct part { int number; char name[NAME_LEN+1]; int on_hand; struct part *next; }; struct part *inventory = NULL; /* points to first part */ struct part *find_part(int number); void insert(void); void search(void); void update(void); void print(void); void erase(void); /********************************************************** * main: Prompts the user to enter an operation code, * * then calls a function to perform the requested * * action. Repeats until the user enters the * * command 'q'. Prints an error message if the user * * enters an illegal code. * **********************************************************/ int main(void) { char code; for (;;) { printf("Enter operation code: "); scanf(" %c", &code); while (getchar() != '\n') /* skips to end of line */ ; switch (code) { case 'i': insert(); break; case 's': search(); break; case 'u': update(); break; case 'p': print(); break; case 'e': erase(); break; case 'q': return 0; default: printf("Illegal code\n"); } printf("\n"); } } /********************************************************** * find_part: Looks up a part number in the inventory * * list. Returns a pointer to the node * * containing the part number; if the part * * number is not found, returns NULL. * **********************************************************/ struct part *find_part(int number) { struct part *p; for (p = inventory; p != NULL && number > p->number; p = p->next) ; if (p != NULL && number == p->number) return p; return NULL; } /********************************************************** * insert: Prompts the user for information about a new * * part and then inserts the part into the * * inventory list; the list remains sorted by * * part number. Prints an error message and * * returns prematurely if the part already exists * * or space could not be allocated for the part. * **********************************************************/ void insert(void) //Insert function that is saying the part already exists { struct part *cur, *prev, *new_node; new_node = malloc(sizeof(struct part)); if (new_node == NULL) { printf("Database is full; can't add more parts.\n"); return; } printf("Enter part number: "); scanf("%d", &new_node->number); for (cur = inventory, prev = NULL; cur != NULL && new_node->number > cur->number; prev = cur, cur = cur->next) ; if (cur != NULL && new_node->number == cur->number) { printf("Part already exists.\n"); free(new_node); return; } printf("Enter part name: "); read_line(new_node->name, NAME_LEN); printf("Enter quantity on hand: "); scanf("%d", &new_node->on_hand); new_node->next = cur; if (prev == NULL) inventory = new_node; else prev->next = new_node; } /********************************************************** * search: Prompts the user to enter a part number, then * * looks up the part in the database. If the part * * exists, prints the name and quantity on hand; * * if not, prints an error message. * **********************************************************/ void search(void) { int number; struct part *p; printf("Enter part number: "); scanf("%d", &number); p = find_part(number); if (p != NULL) { printf("Part name: %s\n", p->name); printf("Quantity on hand: %d\n", p->on_hand); } else printf("Part not found.\n"); } /********************************************************** * update: Prompts the user to enter a part number. * * Prints an error message if the part doesn't * * exist; otherwise, prompts the user to enter * * change in quantity on hand and updates the * * database. * **********************************************************/ void update(void) { int number, change; struct part *p; printf("Enter part number: "); scanf("%d", &number); p = find_part(number); if (p != NULL) { printf("Enter change in quantity on hand: "); scanf("%d", &change); p->on_hand += change; } else printf("Part not found.\n"); } /********************************************************** * erase: Prompts the user to enter a part number. * * Prints an error message if the part doesn't * * exist; otherwise,it deletes the part from * * the database. * **********************************************************/ void erase(void) { //Erase function int number; struct part *p; printf("Enter part number: "); scanf("%d", &number); p = find_part(number); if(p != NULL) { free(p); } else printf("Part not found.\n"); } /********************************************************** * print: Prints a listing of all parts in the database, * * showing the part number, part name, and * * quantity on hand. Part numbers will appear in * * ascending order. * **********************************************************/ void print(void) { struct part *p; printf("Part Number Part Name " "Quantity on Hand\n"); for (p = inventory; p != NULL; p = p->next) printf("%7d %-25s%11d\n", p->number, p->name, p->on_hand); }
Originally Posted by clmoore3
