【发布时间】：2015-04-30 17:09:59
【问题描述】：
大家好，我发现很难找到一种将链表写入现有文本文件的方法。在程序开始时，我从文本文件中读取员工数据并将它们存储在链表中。然后用户可以添加员工。在程序结束时，链表被写入文件，在程序下次加载时更新它。这是我到目前为止所拥有的。任何帮助表示赞赏。
这是我的代码
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define ID_LENGTH 25
#define NAME_LENGTH 25
#define address_LENGTH 25
#define department_LENGTH 25
#define joinDate_LENGTH 25
#define email_LENGTH 30
int mymenu;
//Create employee Structure
typedef struct employee{
char* ID;
char* name;
char* department;
char* address;
char* joinDate;
double salary;
char* email;
struct employee *next;
}employee;
//Declare Function Prototypes
int login();
int Menu();
void Add(struct employee *head);
void search(struct employee *head, char*);
void WriteListToFile(employee *head);
void update(struct employee *head, char*);
void outputList();
struct employee* searchForEmployee(char* );
void savetxt(struct employee *head);
employee* new_employee(char*, char*, char*, char*, char*, double, char*);
employee* insert_by_employee(employee*, employee*);
void removeEmployee(char *);
void print_list(employee*); // prints out the LinkedList
employee* head = NULL;
employee* tail = NULL;
employee* temp = NULL;
employee* current = NULL;
//this stores the employee that comes before the employee that is found by the searchforEmployee
struct employee *empBeforeEmptoDelete = NULL;
int main() {
int num = 0;
FILE *in;
char* ID = (char*)malloc(sizeof(char*) * ID_LENGTH);
char* name = (char*)malloc(sizeof(char*) * NAME_LENGTH);
char* department = (char*)malloc(sizeof(char*) * department_LENGTH);
char* address = (char*)malloc(sizeof(char*) * address_LENGTH);
char* joinDate = (char*)malloc(sizeof(char*) * joinDate_LENGTH);
double salary = 0;
char* email = (char*)malloc(sizeof(char*) * email_LENGTH);
if ((in = fopen("Employees.txt", "r")) == NULL) //Did the file successfully open?
{
printf("The input file failed to open.\n");
printf("Program cannot continue. Exiting. . .\n");
return 1; //Exit Program
}
while (!feof(in)) //Check for file end
{
//Read first data value to kickstart.
if (fscanf(in, "%s %s %s %s %s %lf %s", ID, name, department, address, joinDate, &salary, email) == EOF) {
break;
}
employee* hold = new_employee(ID, name, department, address, joinDate, salary, email);
head = insert_by_employee(head, hold);
}
login();
}
employee* new_employee(char* id, char* name, char* department, char* address, char* joinDate, double salary, char* email) {
//Create new employee and malloc space
employee* new = (employee*)malloc(sizeof(struct employee));
new->ID = (char*)malloc(sizeof(char) * ID_LENGTH);
new->name = (char*)malloc(sizeof(char) * NAME_LENGTH);
new->department = (char*)malloc(sizeof(char) * department_LENGTH);
new->address = (char*)malloc(sizeof(char) * address_LENGTH);
new->joinDate = (char*)malloc(sizeof(char) * joinDate_LENGTH);
new->email = (char*)malloc(sizeof(char) * email_LENGTH);
//Set data
strcpy(new->ID, id);
strcpy(new->name, name);
strcpy(new->department, department);
strcpy(new->address, address);
strcpy(new->joinDate, joinDate);
new->salary = salary;
strcpy(new->email, email);
//Retun a pointer to the node
return new;
}
//Inserts new node into an alphabetically sorted linked list.
employee* insert_by_employee(employee* head, employee* new)
{
employee* current = NULL;
current = head;
if (current == NULL || strcmp(current->department, new->department) > 0)
{
new->next = current;
return new;
}
else {
while (current->next != NULL && strcmp(current->next->department, new->department) < 0)
{
current = current->next;
}
}
new->next = current->next;
current->next = new;
return head;
}
struct employee* searchForEmployee(char* id){
struct employee *empIterator = head;
char i[] = "Employee ID";
char n[] = "Name";
char a[] = "Address";
char d[] = "Department";
char jd[] = "Join Date";
char s[] = "Salary";
char em[] = "Email";
while (empIterator != NULL){
int isEqual = strcmp(empIterator->ID, id);//if the passed in ID is equla to the ID of the node then isEqual will ring true
if (!isEqual){
printf("Employee Found\n");
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", empIterator->ID, empIterator->name, empIterator->address, empIterator->department, empIterator->joinDate, empIterator->salary, empIterator->email);
//printing out the current node which is the desired employee
printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
return empIterator;
}
empBeforeEmptoDelete = empIterator;
empIterator = empIterator->next;
}
printf("%s was not found\n\n", id);
return NULL;
}
void print_list(employee* head)
{
employee* current;
current = head;
char i[] = "Employee ID";
char n[] = "Name";
char a[] = "Address";
char d[] = "Department";
char jd[] = "Join Date";
char s[] = "Salary";
char em[] = "Email";
//Header
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);
printf("--------------------------------------------------------------------------------------------------------------------------------------------\n");
while (current != NULL)
{
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", current->ID, current->name, current->address, current->department, current->joinDate, current->salary, current->email);
current = current->next;
}
printf("-------------------------------------------------------------------------------------------------------------------------------------------\n");
return;
}
//login function takes in user input and compares it the 3
//entries in the Login Struct
int login()
{
char ch;
char username[7];//holds the username
char password[7];//holds the password
int i;
printf("\nPlease enter your Username: ");
gets(username);
printf("\nPlease enter your Password: ");
for (i = 0; i<4; i++)//loop 4 times
{
ch = getch();//get the first character entered for password
password[i] = ch;//insert it into the password array
ch = '*';//change the value of ch to '*'
printf("%c", ch);//print ch which now contains '*' to the screen
}
password[i] = '\0';
struct login{
char name[7];
char password[7];
};
struct login details[3];
fflush(stdin);
FILE *file;
file = fopen("login.txt", "r");
if (file == NULL){
printf("Can not open the file\n");
exit(-1);
}
fflush(stdin);
for (int i = 0; i < 3; i++){
fscanf(file, "%s %s\n", details[i].name, details[i].password);
}
for (int i = 0; i < 3; i++){
if ((strcmp(details[i].name, username) == 0) && (strcmp(details[i].password, password) == 0))
{
printf("\nWelcome %s\n", username);
Menu();
}
fflush(stdin);
}
}
////basic menu function with a switch statement
int Menu()
{
int menuChoice = 0;
int Choice = 9;
while(menuChoice != 8 ){
printf("\n");
printf("1. Add\n");
printf("2. Show\n");
printf("3. Update\n");
printf("4. Delete\n"); // Write a Function for this
printf("5. Departments\n");
printf("6. Employee Report\n");
printf("7. \n");
printf("8. Exit\n\n\n\t\tSELECTION = ");
fflush(stdin);
scanf("%d", &Choice);
fflush(stdin);
switch (Choice)
{
case 1:
{
Add(head);
break;
}
case 2:
{
char text[10];
printf("Enter the text to search for :");
scanf("%s", text);
//search(head, text);
searchForEmployee(text);
break;
}
case 3:
{
char text[10];
printf("Enter the ID to update for :");
scanf("%s", text);
update(head, text);
break;
}
case 4:
{
print_list(head);
char text[10];
printf("Enter the ID to remove :");
scanf("%s", text);
removeEmployee(text);
print_list(head);
break;
}
case 5:
{
print_list(head);
break;
}
case 6:
{
break;
}
case 7:
{
break;
}
case 8:
{
WriteListToFile(head);
exit(0);
break;
}
default:
{
printf("\nInvalid Selection");
break;
}
}
}
system("Pause");
printf("\n\n\n");
return 1; //Exit Success
}
//my add function which validates the email and start date
void Add()
{
char* ID = (char*)malloc(sizeof(char*) * ID_LENGTH);
char* name = (char*)malloc(sizeof(char*) * NAME_LENGTH);
char* department = (char*)malloc(sizeof(char*) * department_LENGTH);
char* address = (char*)malloc(sizeof(char*) * address_LENGTH);
char* joinDate = (char*)malloc(sizeof(char*) * joinDate_LENGTH);
char* tempDate = (char*)malloc(sizeof(char*) * joinDate_LENGTH);
double salary = 0;
char* email = (char*)malloc(sizeof(char*) * email_LENGTH);
char temp[25];
char com[5] = ".com";
int m, d, y;
int daysinmonth[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
int legit = 3;
printf("\nEnter the ID : ");
scanf("%s", ID);
printf("\nEnter the new employee name : ");
scanf("%s", name);
printf("\nEnter their address : ");
scanf("%s", address);
printf("\nEnter their department : ");
scanf("%s", department);
while (legit != 1){
printf("\nEnter their start date : ");
scanf("%s", tempDate);
sscanf(tempDate, "%02d/%02d/%04d", &m, &d, &y);
//printf("%d%d%d",m,d,y);
// leap year checking, if ok add 29 days to february
if (y % 400 == 0 || (y % 100 != 0 && y % 4 == 0))
daysinmonth[1] = 29;
// days in month checking
if (m < 13)
{
if (d <= daysinmonth[m - 1])
legit = 1;
}
if (legit == 1){
printf("\nIt is a legitimate date!\n");
strcpy(joinDate, tempDate);
}
else
printf("\nIt's not a legitimate date!");
}
printf("\nEnter their salary : ");
scanf("%lf", &salary);
printf("\nEnter their email : ");
scanf("%s", temp);
printf(temp);
//I use strchr to check the input for a single '@'
//I then use strstr to check for a substring
while (strchr(temp, '@') == NULL || strstr(temp, com) == NULL)
{
printf("\nThe email doesnt contain an @ sign or .com .");
printf("\nEnter Employee E-Mail: ");
fflush(stdin);
gets(temp);
}
strcpy(email, temp);
employee* hold = new_employee(ID, name, department, address, joinDate, salary, email);
head = insert_by_employee(head, hold);
}
//search by ID or name
void search(struct employee *head, char *crit)//This function takes in the head pointer and a character array pointer
{
int choice;//menu choice tracker
//arrays to hold the header heads
char i[] = "Employee ID";
char n[] = "Name";
char a[] = "Address";
char d[] = "Department";
char jd[] = "Join Date";
char s[] = "Salary";
char em[] = "Email";
//sub menu to filter by ID and Name searches
printf("\nSearch by ");
printf("\n1 : ID");
printf("\n2 : Name\n");
scanf("%d", &choice);
//if the user wants to search by ID
if (choice == 1){
while (head != NULL)
{
//compare the ID to the criteria. If its the same then execute this if
if ((strcmp(head->ID, crit) == 0))
{
//print that we found the employee
printf("Employee Found\n");
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
//printing out the current node which is the desired employee
printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
return;
}
head = head->next;//increments the node until we get to the end of the Linked List
}
printf("Employee not found\n");//Else there is no Employee with an ID of the entered criteria
}
//if the user wants to search by Name
else if (choice == 2){
while (head != NULL)
{
//compare the Name to the criteria. If its the same then execute this if
if ((strcmp(head->name, crit) == 0))
{
//print that we found the employee
printf("Employee Found\n");
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
//printing out the current node which is the desired employee
printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
return;
}
head = head->next;//increments the node until we get to the end of the Linked List
}
printf("Employee not found\n");//Else there is no Employee with an Name of the entered criteria
}
else
printf("Bad input");//Otherwise the user entered a choice out of the range of our handled input
}
//the update function uses the search function then uses a holder to transfer data and then overwrite it
void update(struct employee *head, char *crit)//This function takes in the head pointer and a character array pointer
{
//arrays to hold the header heads
char i[] = "Employee ID";
char n[] = "Name";
char a[] = "Address";
char d[] = "Department";
char jd[] = "Join Date";
char s[] = "Salary";
char em[] = "Email";
char id[25];
char name[25];
char address[25];
char department[25];
char joinDate[25];
double salary;
char email[25];
//if the user wants to search by ID
while (head != NULL)
{
//compare the ID to the criteria. If its the same then execute this if
if ((strcmp(head->ID, crit) == 0))
{
//print that we found the employee
printf("Employee Found\n");
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
//printing out the current node which is the desired employee
printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
printf("\nEnter the ID : ");
scanf("%s", id);
printf("\nEnter the new employee name : ");
scanf("%s", name);
printf("\nEnter their address : ");
scanf("%s", address);
printf("\nEnter their department : ");
scanf("%s", department);
printf("\nEnter their start date : ");
scanf("%s", joinDate);
printf("\nEnter their salary : ");
scanf("%lf", &salary);
printf("\nEnter their email : ");
scanf("%s", email);
strcpy(head->ID, id);
strcpy(head->name, name);
strcpy(head->department, department);
strcpy(head->address, address);
strcpy(head->joinDate, joinDate);
head->salary = salary;
strcpy(head->email, email);
printf("Employee Found\n");
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
//printing out the current node which is the desired employee
printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
return;
}
head = head->next;//increments the node until we get to the end of the Linked List
}
printf("Employee not found\n");//Else there is no Employee with an ID of the entered criteria
}
//this was a secondary function to output the LinkedList. Not the one used in finished solution
void outputList(){
//this was a secondary function to output the LinkedList. Not the one used in finished solution
char i[] = "Employee ID";
char n[] = "Name";
char a[] = "Address";
char d[] = "Department";
char jd[] = "Join Date";
char s[] = "Salary";
char em[] = "Email";
struct employee * employees = head;
printf("Employees Entered\n\n");
while (employees != NULL){
printf("Employee Found\n");
printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", employees->ID, employees->name, employees->address, employees->department, employees->joinDate, employees->salary, employees->email);
printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
employees = employees->next;
}
}//this was a secondary function to output the LinkedList. Not the one used in finished solution
//my remove employee function
void removeEmployee(char* empID){
struct employee* empToDelete = NULL;//this holds the employee we are deleting
empToDelete = searchForEmployee(empID);//we use the search function we made to get the employees details
if (empToDelete != NULL){//if we find him execute this for
printf("%s was deleted\n\n", empID);//let the user know the employee details ahve been deleted
if (empToDelete == head){
head = empToDelete->next;
}
else{
empBeforeEmptoDelete->next = empToDelete->next;
}
free(empToDelete);//Delete the details from memory
}
else//otherwise the employee was not found
{
printf("%s was not found", empID);
}
}
void savetxt(struct employee *head)
{
FILE *f;
f = fopen("Employees.txt", "w+");
if (f == NULL)
{
printf("error");
}
//struct employee *Current = head->next;
while (head != NULL)
{
fprintf(f, "%s\n", head->ID);
fprintf(f, "%s\n", head->name);
fprintf(f, "%s\n", head->address);
fprintf(f, "%s\n", head->department);
fprintf(f, "%s\n", head->joinDate);
fprintf(f, "%lf\n", head->salary);
fprintf(f, "%s\n", head->email);
head = head->next;
}
//head = head->next;
fprintf(f, "\n\n");
fclose(f);
return NULL;
}
void WriteListToFile(employee *head) {
FILE *pFile;
pFile = fopen("Employees.txt", "w");
if (pFile != NULL) {
employee *currentEmp = head;
employee *holdNext = NULL;
while (currentEmp != NULL) {
holdNext = currentEmp->next;
currentEmp->next = NULL;
fseek(pFile, 0, SEEK_END);
fprintf(currentEmp, sizeof(employee), 1, pFile);
printf("Writing:%s to file\n", currentEmp->name);
currentEmp->next = holdNext;
holdNext = NULL;
currentEmp = currentEmp->next;
}
fclose(pFile);
pFile = NULL;
}
else {
printf("FILE OPEN ERROR\n");
}
}EMP1 Martin Computer Clare 06/06/1996 60000 martinemp@gmail.com
EMP2 John Accounting Galway 05/05/1995 50000 johnemp@gmail.com
EMP3 Kevin Computer Kilkenny 04/04/1994 34000 kevinemp@gmail.com
EMP4 Kim Sales Sligo 03/03/1993 65000 kimemp@gmail.com
EMP5 Keith Accounting Ballina 02/02/1992 53200 keithemp@gmail.com
EMP6 Tim Sales Dublin 01/01/1991 23000 timemp@gmail.com
EMP7 Andy Computer Chicago 07/07/1990 10000 andyemp@gmail.com这是登录信息
martin 1234
tim 5678
keith 4321【问题讨论】：
-
您看到了什么问题？
-
嘿嘿基本上程序结束时文件是空的。
-
所以链接列表可能是空的？你看到标准输出上的“try”行了吗？这些字段也可能是空字符串。也打印出来。
-
我有一个功能可以将链表打印到屏幕上。不是空的
-
如果将所有
fprintfs 更改为printf为stdout，是否打印？
标签： c file-io linked-list nodes