This program that I am doing for class to create an EMPLOYEE records file. I created two structs. One called employee and one called date. The EMPLOYEE struct has one char array, one int, 6 float values and DATE(another Struct). The DATE struct has just three int values (month, day, year).
I have created an array of type EMPLOYEE called person[1000].
Here is my code, I keep getting a debug assertion failed error in visual studios pointing to fwrite.c Expression: (Stream !=NULL). I am sure it has to do with my fread or fwite as I have never tried to store structs.
The point of the beginning of this function is to populate the array if the file exists and is not empty, so when the user starts storing data to the array the subscript is updated. I know there are probably a few other issues here but first things first and that would be the reading and writing portion.
Thanks Again,
Mike
void loadPayRoll(EMPLOYEE person[], int *i)
{
char sValidate[5] = "exit";
FILE *f;
int count = 0;
f = fopen("emplyeeRecords.bin", "rb");
if(f){
while(fread(&person[*i], sizeof(person), 1, f) > 0){
(*i)++;
}
fclose(f);
}
else {
while (strcmp( sValidate, person[*i].name)) {
fopen("employeeRecords.bin", "ab+");
printf("Please enter name or type exit to return to main menu: ");
scanf("%s", person[*i].name); //must use the '->' when passing by by refrence, must use '&' sign
flush;
if (!strcmp( sValidate, person[*i].name))
break;
printf("\nPlease enter age of %s: ", person[*i].name);
scanf("%i", &person[*i].age);
flush;
printf("\nPlease enter the hourlyWage for %s: ", person[*i].name);
scanf("%f", &person[*i].hourlyWage);
flush;
printf("\nPlease enter the hours worked for %s: ", person[*i].name);
scanf("%f", &person[*i].hoursWkd);
if (person[*i].hoursWkd > 40) {
person[*i].regPay = person[*i].hoursWkd * 40;
person[*i].otHoursWkd = person[*i].hoursWkd - 40;
person[*i].otPay = person[*i].otHoursWkd * (person[*i].hourlyWage * 1.5);
person[*i].totalPay = person[*i].regPay + person[*i].otPay;
}
else {
person[*i].totalPay = person[*i].hoursWkd * person[*i].hourlyWage;
}
flush;
printf("\nEnter 2 digit month: ");
scanf("%i", &person[*i].payDate.month); //must use the '->' when passing by by refrence, must use '&' sign
flush;
printf("\nEnter 2 digit day: ");
scanf("%i", &person[*i].payDate.day); //must use the '->' when passing by by refrence, must use '&' sign
flush;
printf("\nEnter 4 digit year: ");
scanf("%i", &person[*i].payDate.year); //must use the '->' when passing by by refrence, must use '&' sign
flush;
fwrite(&person[*i], sizeof(person), 1, f);
fclose(f);
(*i)++;
}
}
}//end function loadPayRoll
I'm pretty sure this:
fopen("employeeRecords.bin", "ab+");
sitting all by its lonesome on a single line without assigning the resulting FILE* has quite a bit to do with your problem.There are plenty of other issues for example:
flush;
Not really sure what thats all about. Perhaps you meant:
fflush(f);
Assuming f is ever actually assigned correctly,
And as pointed out in-comment, you should open the file before the loop starts, then write the data as needed, the close it after the loop is finished.
Related
I have declared a structure that has both integer and string type variables. I am able to scan the data and print it without issues. But when I try to write the structure to the file it only reads the strings and I don't understand why.
Here's the structure:
struct employee_details
{
char name[45];
int id;
char designation[30];
long long int phone_number;
char address[75];
}employee;
Here's the function used to get structure input:
void get_employee_details()
{
printf("\nName: ");
scanf("%s", employee.name);
printf("ID: ");
scanf("%d", &employee.id);
printf("Designation: ");
scanf("%s", employee.designation);
printf("Phone Number: ");
scanf("%lld", &employee.phone_number);
printf("Address: ");
scanf("%s", employee.address);
}
Here's the function to write this data in the file:
void add_employee(int is_first_record, int to_append)
{
FILE* p_wfile;
if (to_append == 0)
{
if (is_first_record == 1)
p_wfile = fopen("Record.txt", "w");
else
p_wfile = fopen("Record.txt", "a");
}
else
p_wfile = fopen("Record.txt", "a");
if (p_wfile == NULL)
{
printf("Can't open file.");
exit(1);
}
printf("\nADD EMPLOYEE's DETAILS\n");
get_employee_details();
fwrite(&employee, sizeof(struct employee_details), 1, p_wfile);
if (fwrite == 0)
printf("Error writing to file!\n");
fclose(p_wfile);
}
I have a loop in main() to repeat the writing process until the user wants to but no matter how many structures I input, only the characters get written.
What should I do? Is it somehow related to me using scanf() instead of the better functions?
I guess you are trying to read the file using a text editor.
Issue is with fwrite:
"fwrite" will write the numbers without converting it to ASCII or utf-8 chars hence numbers won't be found when opened via file editor. Instead, you will find a characters equivalent of the numbers stored. Try reading the file using "fread" you will get the actual values back into the "employee_details" structure.
Incase you want to read the data via file editor: use fprint
Try something Like:
fprintf(p_wfile , "%s %d\n", employee.name, employee.id);
So I have a list of names and corresponding phone numbers, and I want the user to be able to continuously enter a new name-number pair into that list. The part of my code where I try to do that looks something like this:
char name[20], list_names[1000][20], phone[20], list_phone[1000][20];
int n;
n = 0;
do
{
printf("Enter name: ");
scanf("%20[^\n]", name);
printf("Enter phone number of %s: ", name);
scanf("%20[^\n]", phone);
strcpy(list_names[n], name);
strcpy(list_phone[n], phone);
n += 1;
}
while (n < 1000);
This usually gives me an error like "incompatible pointer type". I have to do it the indirect way and first store the name in a separate variable. But how do I get the string from that variable into the list? Probably there's something I don't get in the strcpy() part.
Thanks for helping out!
try this
printf("Enter name: ");
scanf(" %19[^\n]", name);//add one space and turn 20 to 19 (leave space for '\0')
printf("Enter phone number of %s: ", name);
scanf(" %19[^\n]", phone);
I'm trying to make a program that can store certain information in a text file. The problem I have though is that with the code I've written so far, the information stored is a bunch of weird symbols and characters. I've managed to kind of find out where it happens from but I can't seem to solve it. It seems like in my register_item function, both item number and balance get weird values for some reason. If anyone can see what mistake I've made, that would be appreciated.
#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>
#define MAX 20
struct vara
{
int itemnumber[20];
char name[30];
int balance[20];
};
open_file(FILE *ange_filnamn, char filnamn[], struct vara varor[], int *antal_varor)
{
int mainmenu = 0;
while (mainmenu != 1 && mainmenu != 2)
{
printf("Do you want to open an existing file (1) or create a new one (2)?\n");
scanf("%d", &mainmenu);
//system("CLS");
if(mainmenu==1)
{
printf("Choose filename (ex. .txt).\n");
scanf("%s", filnamn);
ange_filnamn=fopen(filnamn, "r+");
while(!feof(ange_filnamn))
{
fread(&varor[*antal_varor], sizeof(struct vara), 1, ange_filnamn);
if(!feof(ange_filnamn))
{
*antal_varor=*antal_varor + 1;
}
}
printf("\nNumber of items: %d \n",*antal_varor);
fclose(ange_filnamn);
}
if(mainmenu==2)
{
printf("What name do you want for your new file?\n");
scanf("%s", filnamn);
ange_filnamn=fopen(filnamn, "w+");
printf("File is created!\n");
*antal_varor = 0;
fclose(ange_filnamn);
}
}
}
register_item(struct vara *varor, int *antal_varor)
{
printf("Item number:\n");
scanf("%d", varor[*antal_varor].itemnumber);
printf("Name:\n");
scanf("%s", varor[*antal_varor].name);
printf("Balance:\n");
scanf("%d", varor[*antal_varor].balance);
*antal_varor+=1;
}
print_item(struct vara varor[], int antal_varor)
{
int i;
for (i=0; i < antal_varor; i++)
{
printf("%d. Item number: %d Name: %s Balance: %d\n", i, varor[i].itemnumber, varor[i].name, varor[i].balance);
}
}
quit_program(char filnamn[], struct vara varor[], int *antal_varor)
{
FILE *fil;
//printf("%s", filnamn);
fil=fopen(filnamn, "w+");
fwrite(varor, sizeof(struct vara), *antal_varor, fil);
fclose(fil);
}
int main(void)
{
FILE *ange_filnamn;
struct vara varor[MAX];
int mainmenu, menu, antal_varor=0;
char filnamn[20], filen[30];
open_file(ange_filnamn,filnamn, varor, &antal_varor);
//Second menu
while(menu!=7)
{
printf("\n");
printf("1. Register new items to inventory.\n");
printf("2. Print all items from inventory.\n");
printf("3. Search for item.\n");
printf("4. Change inventory.\n");
printf("5. Sort inventory.\n");
printf("6. Deregister item from inventory.\n");
printf("7. Quit.\n");
scanf("%d", &menu);
if(menu==1)
{
register_item(varor, &antal_varor);
}
if (menu==2)
{
print_item(varor, antal_varor);
}
if (menu==3)
{
printf("test");
}
if (menu==4)
{
printf("test");
}
if (menu==5)
{
printf("test");
}
if(menu==6)
{
printf("test");
}
if (menu==7)
{
quit_program(filnamn, varor, &antal_varor);
}
}
}
You have an array of structures. The array contains antal_varor number of structures, and each structure contains members (elements) itemnumber, name, and balance.
Before we get started, a little side note: I think your structure definition has some bugs. Based on the way you're using it, I think you want
struct vara
{
int itemnumber;
char name[30];
int balance;
};
But your question was about writing the file out. When you call
fwrite(varor, sizeof(struct vara), *antal_varor, fil);
you are writing out the entire array, all at once, in "binary", which is why you can't read it. If you want to write it out in a more human-readable form, you can do something like this. Here I have an explicit loop over the elements of the array, and each time through the loop, I print out all the members of that element:
int i;
for(i = 0; i < *antal_varor; i++ {
fprintf(fil, "varor %d:\n", i);
fprintf(fil, " itemnumber: %d\n", varor[i].itemnumber);
fprintf(fil, " name: %s\n", varor[i].name);
fprintf(fil, " balance: %d\n", varor[i].balance);
}
So, first try that. You should find that the output file is perfectly readable.
Now, the problem is that since you wrote the file out in this nicer, more readable format, your code that reads the data back in, that used to use
fread(&varor[*antal_varor], sizeof(struct vara), 1, ange_filnamn);
is not going to work any more. But here is the sort of code you could use to read the new-format file back in. This code reads the file line by line with fgets, figuring out what each line is, and plugging data items one by one into the varor array to rebuild it.
char line[80];
int i = 0;
*antal_varor = 0;
while(fgets(line, sizeof(line), ange_filnamn) != NULL) {
if(strncmp(line, "varor ", 6) == 0) {
sscanf(line, "varor %d:", &i);
if(i >= MAX) {
fprintf(stderr, "warning: index in file too large\n");
i = 0;
continue;
}
if(i + 1 > *antal_varor) *antal_varor = i + 1;
} else if(strncmp(line, " itemnumber:", 12) == 0) {
sscanf(line, " itemnumber: %d", &varor[i].itemnumber);
} else if(strncmp(line, " name:", 6) == 0) {
sscanf(line, " name: %s", varor[i].name);
} else if(strncmp(line, " balance:", 9) == 0) {
sscanf(line, " balance: %d", &varor[i].balance);
} else {
fprintf(stderr, "warning: unrecognized line in file\n");
}
}
printf("\nNumber of items: %d \n",*antal_varor);
fclose(ange_filnamn);
I haven't tested this, so there may be some little mistakes in it, but it should give you the idea.
(Also there are better ways of writing this sort of thing, but they're a little more elaborate or require more infrastructure, so I've stuck to something very simple and understandable, although it's less than robust.)
The commenters on your question have it right.
- What is displayed with printf (and written to a file with fprintf) is ASCII representation of the numbers.
- What is stored in memory (and written with fwrite) is the actual "binary" value.
In C, an int variable always takes up the same number of bytes in memory, regardless of the value stored. That is why your sizeof() works consistently. Reading and writing can be consistently done.
(Note that not all C implementations use the same size int though. It is 4 bytes in the x86 Linux I'm using right now).
When displaying the ASCII representation, the number of ASCII digit characters required depends on the value. So, if reading values in that have been stored this way, you have to 'parse' the text and build up the integer value from the digits read, and in general will be a variable number of digits. (This is what scanf does.) Hence, reading and parsing ASCII could be considered more complicated than just reading in a value stored as binary int that is always the same size.
IMPORTANT: If you are going to read the file as binary, you should open it with the "b" attribute like this:
ange_filnamn=fopen(filnamn, "r+b");
Similary, to open for binary write:
fil=fopen(filnamn, "w+b");
Essentially, I printed to a binary file using fseek() and fwrite(). However, I want to read the contents from a specific line into a structure. I also used fseek() and fread() to obtain the contents. I prompted the user to enter a code. From what I have learnt, I would use the value obtained from the user to use in the fseek function to get the specific line to start read from. Apparently, the fseek to read the contents does not work, I am getting gibberish essentially when it is displayed on the screen. Assistance is greatly appreciated.
#include <conio.h>
#include <stdio.h>
typedef struct registered
{
int compcode;
char compname[20];
int pinID;
int custID;
char IDtype[15];
int compID;
}REGISTERED;
void AddUpdate(REGISTERED info);
void SellPetrol();
void main(){
REGISTERED info = {0, "Apple", 0, 0, "passport", 0};
REGISTERED list;
AddUpdate(info);
SellPetrol();
}
void AddUpdate(REGISTERED info){
int choice;
FILE *registryfile = NULL;
registryfile = fopen("Sales.dat", "ab");
if (registryfile == NULL){
perror("Error: ");
}
else{
do{
printf("Company Code: ");
scanf("%d", &info.compcode);
printf("Company Name: ");
scanf("%s", &info.compname);
printf("Pin: ");
scanf("%d", &info.pinID);
printf("Customer ID: ");
scanf("%d", &info.custID);
printf("ID type: ");
scanf("%s", &info.IDtype);
printf("Company ID: ");
scanf("%d", &info.compID);
fseek(registryfile, (info.compcode - 1) * sizeof(REGISTERED), SEEK_SET);
fwrite(&info, sizeof(REGISTERED), 1, registryfile);
printf("Enter choice: ");
scanf("%d", &choice);
}while(choice == 1);
}
printf("\tCompany Code: %d\t\n", info.compcode);
printf("\tCustomer ID: %d\t\n", info.custID);
fclose(registryfile);
}
void SellPetrol(){
int code = 0, PIN;
REGISTERED list;
FILE *registryfile = NULL;
registryfile = fopen("Sales.dat", "rb");
if (registryfile == NULL){
perror("Error: ");
}
else{
printf("Please enter the company code: ");
scanf("%d", &code);
// printf("Please enter the PIN: ");
// scanf("%d", &PIN);
rewind(registryfile);
fseek(registryfile, (code - 1) * sizeof(REGISTERED), SEEK_SET);
fread(&list, sizeof(REGISTERED), 1, registryfile); //reads data into list
fflush(stdin);
printf("Company Code: %d\n", list.compcode);
printf("Company Name: %s\n", list.compname);
printf("Pin: %d\n", list.pinID);
printf("Customer ID: %d\n", list.custID);
printf("ID Type: %s\n", list.IDtype);
printf("Company ID: %d\n", list.compID);
}
fclose(registryfile);
}
It seems whichever method you're using to learn C is causing troubles, as the mistakes you seem to be making are common. I suggest reading a book, such as K&R2E... Do the exercises as you stumble across them; don't move on until you've completed them, and ask questions about them if necessary.
Don't fflush(stdin). fflush doesn't do what you think it does.
Check return values for functions such as fopen, scanf, fseek, fread, even fwrite. You'll probably find that your fread or scanf is returning a value indicating failure, hence the gibberish you speak of.
Be aware that C uses pass-by-value semantics ONLY. The source of at least one error in your code is a misunderstanding regarding these semantics. Namely, AddUpdate has no way to modify the variable declared within main, as it recieves a copy of that variable; at this point it seems void AddUpdate(REGISTERED info) should be void AddUpdate(void) and info should be declared within AddUpdate.
scanf("%s", &info.compname); probably doesn't do what you think it does. The %s directive tells scanf to read (metalinguistically speaking) a word (that is, a whitespace-delimitered token), not a line (a newline delimitered token), of user input. You probably want int x = scanf("%19[^\n]", info.compname); or better yet, char *x = fgets(info.compname, sizeof info.compname, stdin);...
void main() is unportable, and so is #include <conio.h>. You probably want int main(void) and ... you don't appear to be using any functions from <conio.h>, so you probably don't want anything in place of that. In C99, a main function that has no return statement will implicitly return 0; without a warning issued.
Yes ,I know that this question was already asked for many times ,but none of these helped me to discover the problem (duplicate...yeah). I want to read from input a series of strings into an array and then search from 'First Name'. If the name exist ,I want to display all the data stored in that element of array (I attached the code to undestand easily). When I run it ,I read from keyboard all the data ,but it returns me absolutely nothing.
#include<stdio.h>
typedef struct record {
char name[10],lname[10],phone[10],bday[10];
};
void main() {
struct record rec;
char search;
int i,nr;
printf("\nInput number of records: ");
scanf("%d",&nr);
for (i=0 ; i<nr ;i++) {
printf("First name: ");
scanf("%s",&rec.name[i]);
printf("Last name: ");
scanf("%s",&rec.lname[i]);
printf("Phone: ");
scanf("%s",&rec.phone[i]);
printf("Bday: ");
scanf("%s",&rec.bday[i]);
}
printf("Input the first name for searching: ");
scanf("%s",&search);
for (i=0 ;i<nr;i++) {
if (search == rec.name[i]) {
printf("First name: %s\nLast name: %s\nPhone: %s\nB-day: %s",rec.name[i],rec.lname[i],rec.phone[i],rec.bday[i]);
}
}
}
NOTE: I already replaced
scanf("%s",&rec.name[i]);
with
scanf("%s",rec.name[i]);
but no effect.
I believe there are a lot of problems with your code.
Firstly in this line:
scanf("%s",&search);
You have declared search as only a char, when really you want an array of chars. You also don't need & with search, as an array decays to a pointer to the first element.
It instead should be like this:
char search[10];
scanf("%9s", search); /* %9s to avoid buffer overflow */
You need to make this change to all your other scanf() calls, as this seems to be everywhere in this code.
It also seems that you want to create an array of records(structures), So you might need to make this after getting the value of nr. You can create it like this:
struct record rec[nr]; /* array of nr structures */
This also means calls like this:
rec.name[i]
Don't make sense, as you are iterating over the characters within a name, not over all the records in struct records.
This needs to be instead:
rec[i].name
Secondly, Your using == to compare strings, when you should be using strcmp instead. Using == will only compare the base address of the strings, not the actual contents of strings.
Your line should be this instead:
if (strcmp(search, rec[i].name) == 0) {
If you read the manual page for strcmp(), checking for a return value of 0 means that both strings are equal in comparison.
Lastly, in your first scanf() call:
scanf("%d",&nr);
You should really check the return value of this:
if (scanf("%d", &nr) != 1) {
/* exit program */
}
Note: For reading strings, you should really be using fgets instead. You can try upgrading to this later, but I think it is better to understand these basics first.
Here is working example of what your program should do:
#include <stdio.h>
#include <string.h>
#define STRSIZE 10
typedef struct {
char name[STRSIZE+1]; /* +1 to account for null-btye at the end */
char lname[STRSIZE+1];
char phone[STRSIZE+1];
char bday[STRSIZE+1];
} record;
int main() {
char search[STRSIZE+1];
int i,nr;
printf("\nInput number of records: ");
if (scanf("%d", &nr) != 1) {
printf("Invalid input.\n");
return 1;
}
record rec[nr]; /* array of records */
for (i = 0; i < nr ; i++) {
printf("First name: ");
scanf("%10s", rec[i].name);
printf("Last name: ");
scanf("%10s", rec[i].lname);
printf("Phone: ");
scanf("%10s", rec[i].phone);
printf("Bday: ");
scanf("%10s", rec[i].bday);
}
printf("Input the first name for searching: ");
scanf("%10s", search);
for (i = 0; i < nr; i++) {
if (strcmp(search, rec[i].name) == 0) {
printf("First name: %s\nLast name: %s\nPhone: %s\nB-day: %s\n",rec[i].name,rec[i].lname,rec[i].phone,rec[i].bday);
} else {
printf("Record not found.\n");
}
}
return 0;
}
The numeric input leaves a new line character in the input buffer, which is then picked up by the character input. when numeric input with scanf() skips leading white space, character input does not skip this leading white space.
Use a space before %c and it will help you cause if space is not used then a buffer added with value .so that use space before %c
scanf(" %c",&rec.name[i]);