I have a problem with a function which should write a struct to a file, the files are created however they stay empty whatever I do.
This is the struct that I'm trying to write to the file:
typedef struct
{
double dA;
double dA1;
double dB;
double dB1;
double dAwnser;
char cStepOne[24];
char cStepTwo[24];
char cStepThree[20];
char cFormula[26];
} equationData_t;
equationData_t equation;
This is the function to write the struct to a file:
void writeDataToFile(equation)
{
int iSizeOfStruct = 0;
char cFileName[20];
int iQuitProgram = 0;
iSizeOfStruct = sizeof(equationData_t);
while (1)
{
printf("Give file name with extension (Max 20 char.):\n:");
scanf("%s",&cFileName[0]);
pnf = fopen(cFileName, "r+");
if (pnf == NULL)
{
printf ("\nError: File not found!\n1.Try again.\n2.Quit.\n3.Make new file.\n:");
scanf("%d",&iQuitProgram);
switch(iQuitProgram)
{
case 1: break;
case 2: exit(1);
case 3: makeNewFile();
}
}
if (pnf != NULL)
{
printf("\n************************************\nFile opend!\nWriting data to file.\n");
fwrite(equation, iSizeOfStruct, 1, pnf);
fclose(pnf);
printf("Data written");
break;
}
}
}
You can try to use open() and then pwrite() instead of fopen() and the fwrite().
However, in your code:
fwrite(equation, iSizeOfStruct, 1, pnf);
should be modified in:
fwrite(&equation, iSizeOfStruct, 1, pnf);
Related
I'm working on the last exercise of the "Think like a computer scientist, C version" book and I have some trouble with one particular point.
The exercise consists of making a small game, where the computer picks a random value between 0 and 20 and then asks me to guess the number.
After that, the computer counts the number of tries I made and, if I get a better score than the previous party, I need to store my name and the number of tries in a structure.
My problem is the following: When I restart the game, the string value, player_name, in the structure gets somehow deleted but player_score is still there.
First, I made a "call by value" function to create the structure and then a tried with a "call by reference" but getting the same results.
I think I tried everything I could with my actual knowledge for now; so, if someone could check my code and give me some tips about what's wrong I would much appreciate it!
//HEADERS
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define FALSE 0
#define TRUE 1
//TYPEDEF STRUCTS
typedef struct
{
int player_score;
char *player_name;
} HS_Player;
//FUNCTION PROTOTYPES
int Random_Value(void);
int Get_User_Choice(void);
int Check_Result(int computer, int my_choice);
int Try_Again(int game_result, int computer);
void Player_Infos(HS_Player *player_p, int score);
int Game_Restart(void);
//MAIN
int main(void)
{
int end_game;
int high_score_value = 100;
HS_Player player;
while (end_game != TRUE)
{
int computer_number = Random_Value();
printf("Guess the number between 0 et 20 chosen by the computer.\n");
int your_number = Get_User_Choice();
int result_game = Check_Result(computer_number, your_number);
int tries_to_win = Try_Again(result_game, computer_number);
printf("Number of tries: %i\n", tries_to_win);
if (tries_to_win < high_score_value)
{
Player_Infos(&player, tries_to_win );
high_score_value = player.player_score;
}
printf("Highest score: %i By: %s\n", player.player_score, player.player_name);
printf("\n");
end_game = Game_Restart();
}
return EXIT_SUCCESS;
}
//Random_Value FUNCTION
int Random_Value(void)
{
srand(time(NULL));
int x = rand();
int y = x % 20;
return y;
}
//Get_User_Choice FUNCTION
int Get_User_Choice(void)
{
int success, x;
char ch;
printf("Your Guess:\t");
success = scanf("%i", &x);
while (success != 1)
{
printf("Your input is not a number. Please try again:\t");
while ((ch = getchar()) != '\n' && ch != EOF);
success = scanf("%i", &x);
}
if (x < 0 || x > 20)
{
printf("Your input must be between 0 and 20. Please try again.\n");
Get_User_Choice();
}
return x;
}
//Check_Result FUNCTION
int Check_Result(int computer, int my_choice)
{
int check_result;
if (my_choice < computer)
{
printf("Computer number is larger!\n");
check_result = FALSE;
}
else if (my_choice > computer)
{
printf("Computer number is smaller!\n");
check_result = FALSE;
}
else if (my_choice == computer)
{
printf("It's a Match! You chose the same number than the computer.\n");
printf("\n");
check_result = TRUE;
}
return check_result;
}
//Try_Again FUNCTION
int Try_Again(int game_result, int computer)
{
int tries_befor_success = 1;
while (game_result != TRUE)
{
int your_number = Get_User_Choice();
game_result = Check_Result(computer, your_number);
tries_befor_success++;
}
return tries_befor_success;
}
//Player_Infos FUNCTION
void Player_Infos(HS_Player *player_p, int score)
{
char new_name[80];
printf("Congrats! Your made a new high score.\n");
printf("What's your name ?\t");
scanf("%s", new_name);
printf("\n");
player_p->player_score = score;
player_p->player_name = new_name;
}
//Game_Restart FUNCTION
int Game_Restart(void)
{
int quit_value;
printf("Quit Game ?\n");
printf("Press 'y' to quit or any other keys to continue.\n");
fflush(stdin);
char quit_game = getchar();
printf("\n");
if (quit_game == 'y')
{
quit_value = TRUE;
}
else
{
quit_value = FALSE;
}
return quit_value;
}
The problem is that, in your Player_Infos function, you are assigning the address of a local array to the char* player_name pointer member of the passed structure. When that function ends, the local array it used will be deleted and the pointer in the structure will be invalid. (In the case of the player_score, you don't have that problem, because the given value is copied to the structure member.)
There are several ways around this; one would be to use the strdup() function to make a copy of the local char new_name[80]; array – but that is really overkill, and you would need to manage (i.e. free()) that allocated string whenever you make a modification.
A simpler way is to make the player_name member an actual array of char and then use strcpy() to copy the local array into that member.
Better, still, with the player_name member defined as char [80], you can read directly into that (in the function), and avoid the local array completely:
typedef struct
{
int player_score;
char player_name[80];
} HS_Player;
//...
void Player_Infos(HS_Player *player_p, int score)
{
printf("Congrats! Your made a new high score.\n");
printf("What's your name ?\t");
// Read directly. Limit input to 79 chars (allowing room for null terminator).
scanf("%79s", player_p->player_name);
printf("\n");
player_p->player_score = score;
}
Also, just as a "style" tip, you may want to change the member names to just score and name, as the "player" part is implied by the structure type-name itself.
This issue you are having is that you are associating the player name pointer to a variable that goes out of scope when you leave the "player_Infos" function. What you probably would want to do is define the name as a character array in your structure and then use the "strcpy" call in your function instead. Following is a couple of code snippets illustrating that point.
//TYPEDEF STRUCTS
typedef struct
{
int player_score;
char player_name[80];
} HS_Player;
Then, in your function, use the "strcpy" call.
//Player_Infos FUNCTION
void Player_Infos(HS_Player *player_p, int score)
{
char new_name[80];
printf("Congrats! Your made a new high score.\n");
printf("What's your name ?\t");
scanf("%s", new_name);
printf("\n");
player_p->player_score = score;
strcpy(player_p->player_name, new_name);
//player_p->player_name = new_name;
}
When I tested that out, I got a name to appear in the terminal output.
Computer number is smaller!
Your Guess: 4
It's a Match! You chose the same number than the computer.
Number of tries: 8
Highest score: 4 By: Craig
FYI, you will need to include the "string.h" file.
Give that a try.
Name Update
The reason your player.player_name is not getting updated is because you can't assign a string this way in C. When doing player_p->player_name = new_name; you're actually saving in player_p->player_name the memory address of new_name.
Instead, what you want to achieve, is to copy each character of new_name to player_p->player_name and in order to achieve this, you have to change the type of prlayer_name field from char* player_name to char player_name[80], then assign it using, for example, strcpy():
#include <string.h>
// [...]
//TYPEDEF STRUCTS
typedef struct
{
unsigned int player_score;
char player_name[80];
} HS_Player;
// [...]
//Player_Infos FUNCTION
void Player_Infos(HS_Player *player_p, int score)
{
char new_name[80];
printf("Congrats! Your made a new high score.\n");
printf("What's your name ?\t");
scanf("%s", new_name);
printf("\n");
player_p->player_score = score;
strcpy(player_p->player_name, new_name);
}
Data Persistence
To make data (players info) persistent over multiple runs, you have to save the content of the struct to a file.
Example
int Save_Score(char* filename, HS_Player* player)
{
FILE* file = fopen(filename, "w");
if (file == NULL)
{
fprintf(stderr, "\nAn error occurred while opening the file\n");
return -1;
}
if (fprintf(file, "%d %s", player->player_score, player->player_name) < 0)
return -1;
fclose(file);
return 0;
}
int Load_Score(char* filename, HS_Player* player)
{
FILE* file = fopen(filename, "r");
if (file == NULL)
{
fprintf(stderr, "\nAn error occurred while opening the file\n");
return -1;
}
if (fscanf(file, "%d %79s", &player->player_score, player->player_name) < 0)
return -1;
fclose(file);
return 0;
}
Im trying to scanf a structure from file input within a function, and print it using another function.
Ultimately I need to be able to print out the same information that I would from the code that I commented out, but doing so from the functions I have listed in the function prototypes declaration area. I only un-commented 2 of those so I could try baby steps to get something to scan and print using functions. The functions themselves are located at the very bottom.
To finish the scan_auto function, somehow I need to scanf 2 other structures that are part of the main structure. I assume I need to call the functions scan_date and scan_tank from scan_auto, however I am unsure how to do that properly.
Here is the code I have so far...
#include <stdio.h>
#define STRSIZE 20
/* Structure definitions */
typedef struct {
int month,
day,
year;
} date_t;
typedef struct {
double capacity,
current;
} tank_t;
typedef struct {
char make[STRSIZE],
model[STRSIZE];
int odometer;
date_t manuf,
purch;
tank_t tank;
} auto_t;
/* Function prototypes */
/*
int scan_date(date_t *date);
int scan_tank(tank_t *tank);
*/
int scan_auto(auto_t *vehicle, FILE *inp);
/*
void print_date(date_t date);
void print_tank(tank_t tank);
*/
void print_auto(auto_t vehicle);
int main()
{
auto_t vehicle;
int number=0,
i=0,
status=1;
FILE *inp = fopen("autos.txt","r"); /* defining file input */
/* Check to make sure input file is found and readable. */
if(inp==NULL){
printf("Error: Input file - autos.txt - not found!\n");
getch();
return 0;
}
printf("Vehicle Vehicle Odometer Date Date Tank Current\n");
printf("Make Model Reading Purchased Manufactured Capacity Fuel Level\n");
printf("\n----------------------------------------------------------------------------\n\n");
/*******************COMMENTED OUT*************************************
while(status>0){
status=fscanf(inp, "%s%s%d%d%d%d%d%d%d%lf%lf", vehicle.make,
vehicle.model,
&vehicle.odometer,
&vehicle.manuf.month,
&vehicle.manuf.day,
&vehicle.manuf.year,
&vehicle.purch.month,
&vehicle.purch.day,
&vehicle.purch.year,
&vehicle.tank.capacity,
&vehicle.tank.current);
if(status==11){
printf("%-10s%-9s%-10d%2d/%d/%-6d%2d/%d/%-8d%-11.1lf%.1lf\n", vehicle.make,
vehicle.model,
vehicle.odometer,
vehicle.manuf.month,
vehicle.manuf.day,
vehicle.manuf.year,
vehicle.purch.month,
vehicle.purch.day,
vehicle.purch.year,
vehicle.tank.capacity,
vehicle.tank.current);
i++;}
else if(status <11 && status>0){
printf("\nInvalid Input - The next line of data is corrupt.\n");
}
}
******************************************************************************/
scan_auto(&vehicle, inp);
print_auto(vehicle);
/*
print_auto(vehicle);
*/
getch();
return 0;
}
/*********************************************************************************/
int scan_date(date_t *date)
{
int result;
result=scanf("%d%d%d", &(*date).month,
&(*date).day,
&(*date).year);
if (result==3)
result=1;
else if(result !=EOF)
result=0;
return (result);
}
/*********************************************************************************/
double scan_tank(tank_t *tank)
{
int result;
result=scanf("%lf%lf", &(*tank).capacity,
&(*tank).current);
if (result==2)
result=1;
else if(result !=EOF)
result=0;
return (result);
}
/*********************************************************************************/
int scan_auto(auto_t *vehicle, FILE *inp)
{
int result;
result=fscanf(inp, "%s%s%d", (*vehicle).make,
(*vehicle).model,
&(*vehicle).odometer);
if (result==3)
result=1;
else if(result !=EOF)
result=0;
return (result);
}
/*********************************************************************************/
void print_auto(auto_t vehicle)
{
printf("%-10s%-9s%-10d", vehicle.make,
vehicle.model,
vehicle.odometer);
}
The text file (autos.txt) I am using....
Mercury Sable 99842 1 18 2001 5 30 1991 16 12.5
Mazda Navajo 123961 2 20 1993 6 15 1993 19.3 16.7
however I am unsure how to do that properly.
Can you elaborate on what you're unsure? If you're not sure how to assign value to struct member of struct, perhaps this sample code will help you? I combined all of the things together...
Oh, and I changed your *vehicle to *v to make it shorter and easier to read.
Also, since you're accessing member of struct pointer, why don't you use v->xxx instead of (*v).xxx ?
UPDATE 1: You asked how to do it separately. Here it is:
int scan_date(date_t *date, FILE *inp)
{
int result = fscanf(
inp,
"%d%d%d",
&(date->day),
&(date->month),
&(date->year));
return (result == 3);
}
int scan_tank(tank_t *tank, FILE *inp)
{
int result = fscanf(
inp,
"%lf%lf",
&(tank->capacity),
&(tank->current));
return (result == 2);
}
int scan_auto(auto_t *v, FILE *inp)
{
int result = fscanf(
inp,
"%s%s%d",
v->make,
v->model,
&(v->odometer));
result += scan_date(&(v->purch), inp);
result += scan_date(&(v->manuf), inp);
result += scan_tank(&(v->tank), inp);
return (result == 11); // return 0 if true
}
The following code doesn't behave as expected ..
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
struct dest
{
char filename[20], keyword[20];
bool opened;
FILE * file;
};
void display_data(const struct dest p) {
printf("Keyword: %s, Filename: %s, Used: %s\n", p.keyword, p.filename, p.opened ? "Yes" : "No");
}
int main(int argc, char const *argv[])
{
// declaring variables
float lon, lat;
char info[80];
FILE *reader;
// checking required arguments
if ((argc+1) % 2 || argc < 2) {
fprintf(stderr, "Usage: %s file_to_read file_for_unknown type file type file ...\n", argv[0]);
return 2;
}
// opening the reader
if (!(reader = fopen(argv[1], "r"))) {
fprintf(stderr, "File can't be accessed: %s\n", argv[1]);
return 2;
}
// creating important globals
const short pairs = (argc-3)/2;
struct dest data[pairs];
struct dest other;
strcpy(other.filename, argv[2]);
other.opened = false;
// gathering data
short times = 4;
for(short i = 4; i < argc; i += 2) {
data[i-times].opened = false;
strcpy(data[i-times].keyword, argv[i-1]);
strcpy(data[i-times].filename, argv[i]);
times += 1;
}
// finally, scanning the file ..
struct dest *use_f; // pointer for the wanted destination ..
bool known;
while (fscanf(reader, "%f,%f,%79[^\n]", &lat, &lon, info)) {
// deciding which file to use ..
known = false;
for(short i=0; i < pairs; ++i) {
if (strstr(info, data[i].keyword)) {
known = true;
use_f = &data[i];
}
}
if (!(known)) {
use_f = &other;
}
// checking the file ..
if (!((*use_f).opened)) {
(*use_f).file = fopen((*use_f).filename, "w");
(*use_f).opened = true;
}
// writing to the file ..
fprintf((*use_f).file, "%f,%f,%s\n", lat, lon, info);
}
// closing all data streams, and informing user ..
for (short i=0; i < pairs; ++i) {
display_data(data[i]);
if (data[i].opened) {
fclose(data[i].file);
data[i].opened = false;
}
}
fclose(reader);
fclose(other.file);
return 0;
}
The command used to run it is this ..
./categorize spooky.csv other.csv UFO UFOS.csv # I get no output at all
It seems that the while loop doesn't actually end, which is mysterious, because the file (spooky.csv) is only 11 lines !
30.685163,-68.137207,Type=Yeti
28.304380,-74.575195,Type=UFO
29.132971,-71.136475,Type=Ship
28.343065,-62.753906,Type=Elvis
27.868217,-68.005371,Type=Goatsucker
30.496017,-73.333740,Type=Disappearance
26.224447,-71.477051,Type=UFO
29.401320,-66.027832,Type=Ship
37.879536,-69.477539,Type=Elvis
22.705256,-68.192139,Type=Elvis
27.166695,-87.484131,Type=Elvis
It just keeps writing to other.file, yet I don't know why ..
The program simply doesn't end, can anybody explain things to me ?
From the fscanf() manpage: "The value EOF is returned if an input failure occurs before any conversion (such as an end-of-file) occurs."
Here's a hint... EOF isn't equal to 0. Your while-loop never terminates.
I've been working on a program for a data structure that reads in a file of different currencies, which I then call to use for conversion. I've been running over this for days on end and tried fgets, fscanfs, and such, and I'm just lost at this point as I am pretty new to programming.
the dat. file is outlined on separate lines like this:
dollar 1.00
yen 0.0078
franc 0.20
mark 0.68
pound 1.96
my code so far:
typedef struct {
string currency;
double rate;
} currencyT;
typedef struct {
currencyT cur[MaxCurrencyTypes];
int nCurrency;
} *currencyDB;
static currencyDB ReadDataBase(void);
static ReadOneLine(FILE *infile, currencyDB db);
static currencyDB ReadDataBase(void)
{
FILE *infile;
currencyDB db;
int nCurrency;
db = New(currencyDB);
infile = fopen(ExchangeFile, "r");
while (ReadOneLine(infile, db));
fclose(infile);
return(db);
}
static ReadOneLine(FILE *infile, currencyDB db)
{
currencyT cur;
char termch, currency;
double rate;
int nscan, nCurrency;
nCurrency = 0;
while(1) {
nscan = fscanf(infile, "%20s %f%c", db->cur[nCurrency].currency,
&db->cur[nCurrency].rate, &termch);
if(nscan = EOF) break;
if(nscan != 3 || termch != '\n') {
Error("Improper file format");
}
nCurrency++;
}
db->nCurrency = nCurrency;
}
static void ProcessExchange(currencyDB db)
{
}
main()
{
currencyDB currencies;
currencies = ReadDataBase();
ProcessExchange(currencies);
}
See 8 & 9 first.
MaxCurrencyTypes is undeclared, let's assume
#define MaxCurrencyTypes (5)
string is undeclared, let's assume
typedef char * string;
currencyDB is a pointer type, recommend instead declaring as a structure type
typedef struct {
currencyT cur[MaxCurrencyTypes];
int nCurrency;
} currencyDB; // Drop *
static ReadOneLine() should use explicit return type.
static int ReadOneLine()
int nCurrency; not used in ReadDataBase().
New() in db = New(currencyDB) is not declared nor defined. Assume to allocate uninitialized memory for *db.
ExchangeFile not declared.
if (nscan = EOF) -> if (nscan == EOF)
ReadOneLine() needs to return a value.
main() should explicitly state return type and parameters.
int main(void)
Hello fellow programmers i am trying to understand what exactly is happening in this area of my code.
Problem: I read some contents into a file , then i am trying to read back the contents out of the file just to make sure its the right contents i had put into the file but it is not giving me the correct output, so i am a little confused here is the code(saved content as binary) :
typedef struct acc
{
int id_no;
int pin;
float bal;
}Acc;
int Crte_acc(FILE *flepss)
{
int i,cnt;
Acc user[1000];
cnt = 1000;
for (i=1;i<1000;i++)
{
cnt+=1;
user[i].id_no = cnt;
user[i].bal=1000;
user[i].pin=0000;
fwrite(&user[i].id_no,sizeof(int),1,flepss);
fwrite(&user[i].pin,sizeof(int),1,flepss);
fwrite(&user[i].bal,sizeof(int),1,flepss);
}
return fclose(flepss);
}
Yea so above is the code that takes a file pointer and a count to keep the id to increase by 1 ( 1001,1002 etc), bal and pin required that i set the var with those digits.So i am wondering whats the problem, this is the code of me displaying the contents.
void DisplyFile()
{
FILE *dfp;
int x;
Acc pruser[1000];
dfp = fopen("Account.dat","rb");
fseek(dfp,0,SEEK_SET);
while (1)
{
if(!feof(dfp))
{
for (x=1;x<1000;x++)
{
fread(&pruser[x].id_no,sizeof(pruser[x].id_no),1,dfp);
fread(&pruser[x].pin,sizeof(pruser[x].pin),1,dfp);
fread(&pruser[x].bal,sizeof(pruser[x].bal),1,dfp);
printf("%d ",pruser[x].id_no);
printf("%d ",pruser[x].pin);
printf("%.2f\n\n",pruser[x].bal);
}
}
else
{
break;
}
}
}
EDIT: By contents coming out wrong i mean , giving me garbage values as to show that my write to file was not saved.
The problem may come from a missing fclose or fopen...
There is almost nothing to do to build something that works.
Three things to check :
-Does a fopen correspond to a fclose ?
-Are opening types similar ? Are both "wb" and "rb" used ?
-Another point is fwrite(&user[i].bal,sizeof(int),1,flepss);...bla is a float. float and int may have the same sizeof, but...It is safer to assume that it is not always the case !
#include <stdio.h>
typedef struct acc
{
int id_no;
int pin;
float bal;
}Acc;
int Crte_acc()
{
FILE *flepss;
int i,cnt;
Acc user[10];
cnt = 1000;
flepss = fopen("Account.dat","wb");
for (i=1;i<10;i++)
{
cnt+=1;
user[i].id_no = cnt;
user[i].bal=10;
user[i].pin=0000;
fwrite(&user[i].id_no,sizeof(int),1,flepss);
fwrite(&user[i].pin,sizeof(int),1,flepss);
fwrite(&user[i].bal,sizeof(float),1,flepss);
}
return fclose(flepss);
}
void DisplyFile()
{
FILE *dfp;
int x;
Acc pruser[10];
dfp = fopen("Account.dat","rb");
fseek(dfp,0,SEEK_SET);
while (1)
{
if(!feof(dfp))
{
for (x=1;x<10;x++)
{
fread(&pruser[x].id_no,sizeof(pruser[x].id_no),1,dfp);
fread(&pruser[x].pin,sizeof(pruser[x].pin),1,dfp);
fread(&pruser[x].bal,sizeof(pruser[x].bal),1,dfp);
printf("%d ",pruser[x].id_no);
printf("%d ",pruser[x].pin);
printf("%.2f\n\n",pruser[x].bal);
}
}
else
{
break;
}
}
fclose(dfp);
}
int main()
{
Crte_acc();
printf("file printed\n");
DisplyFile();
printf("end file read 1\n");
DisplyFile();
printf("end file read 2\n");
return 0;
}
To compile : gcc main.c -o main
Bye,