Thread: User enter text and save to text file (end enter text using -1)

Hi! What I want to do is let the user enter some text until he/she enters -1. Then I want to print what the user wrote to a text file.

Do I somehow overwrite the buffer? I get a text file with 0 kB. So it contains no text at all. How can I make it print all the text the user typed to the file?

Code:

#include <stdio.h>
#include <string.h>
#define SIZE 1000
#define TRUE 1
#define FALSE 0
#define AMT_USERS 1


typedef struct User {
	char buffer[SIZE]; 
	FILE* file;
}User;




void input(User *user);
void printToFile(User *user);


int main() {
	User user[AMT_USERS];
	
	input(user);
	
	return 0;
}


void input(User *user) {
	
	int finished = FALSE;
	
	while (finished == FALSE) {
		
		fgets(user->buffer, SIZE, stdin); 
		
		if (strcmp(user->buffer, "-1\n") == 0) {
			finished = TRUE;
		}
	}
	
	printToFile(user);
}


void printToFile(User *user) {
	user->file = fopen("text.txt", "w");
	
	if (user->file == NULL) {
		perror("Error");
	} 
	
	while (fgets(user->buffer, SIZE, user->file) != NULL) {
		fprintf(user->file, "%s", user->buffer);
	}
	
	fclose(user->file);
}

I see 2 problems with your code:

1. fgets(user->buffer, SIZE, stdin); will override previous value of user->buffer. Better read into a temporary buffer and if input != "-1\n" then add to user->buffer. Be careful not to write over the end from user->buffer.

2. while (fgets(user->buffer, SIZE, user->file) != NULL) Why you do try to read from empty file that is open only for writing ???????
Why don't you just write user->buffer to the file ?

So I decided to try to do what I at least think you meant, if I'm not totally mistaken.

1. So I created a temporary buffer (I hope) and then checks for as long as the input
from the user is not -1. Add the characters to the users buffer (not sure if this step is correct though).
I am aware that I'm still overwriting the buffer.

This worked fine with only printing one sentence, of course, I never overwrite the buffer
then.

2. So I am trying to read in to file. That was not what I thought I were doing.
How do you mean I can use user->buffer to the file?

Code:

#include <stdio.h>
#include <string.h>
#define SIZE 1000
#define TRUE 1
#define FALSE 0
#define AMT_USERS 1


typedef struct User {
    char buffer[SIZE]; 
    FILE* file;
}User;




void input(User *user);
void printToFile(User *user);


int main() {
    User user[AMT_USERS];
    
    input(user);
    
    return 0;
}


void input(User *user) {
    char buffer[SIZE];
    
    int finished = FALSE;
    
    while (finished == FALSE) {
        
        fgets(buffer, SIZE, stdin); 
        
        if (strcmp(buffer, "-1\n") == 0) {
            finished = TRUE;
        }
        
        if (strcmp(buffer, "-1\n") != 0) {        
            int i;
            for (i = 0; i < SIZE; i++) {
                user->buffer[i] = buffer[i];
            }
        }
    }
                
    printToFile(user);


}


void printToFile(User *user) {
    user->file = fopen("text.txt", "w");
    
    if (user->file == NULL) {
        perror("Error");
    } 
    
    //while (fgets(user->buffer, SIZE, user->file) != NULL) {
        fprintf(user->file, "%s", user->buffer);
    //}
    
    fclose(user->file);
}

Try this code:

Code:

#include <stdio.h>
#include <string.h>

#define SIZE 1000
#define TRUE 1
#define FALSE 0
#define AMT_USERS 1


typedef struct User 
{
  char buffer[SIZE];
  FILE* file;
}User;

void input(User *user);
void printToFile(User *user);

int main() 
{
  User user[AMT_USERS] = {0};

  input(user);

  return 0;
}


void input(User *user) 
{
  char buffer[SIZE] = {0};

  int finished = FALSE;

  while (finished == FALSE) 
  {
    fgets(buffer, SIZE, stdin);
    if (strcmp(buffer, "-1\n") == 0) 
      finished = TRUE;
    else
    {
      if (strlen(user->buffer) + strlen(buffer) < SIZE) /* check buffer overflow */
        strcat(user->buffer, buffer);
    }
    
  }
  printToFile(user);
}


void printToFile(User *user) 
{
  user->file = fopen("text.txt", "w");
  if (user->file == NULL) 
  {
    perror("Error");
    return;
  }
  fprintf(user->file, "%s", user->buffer);
  fclose(user->file);
}

I get what you mean laserlight but in my assignment it sais that I should create
a buffer with a large size, but of course it doesn't print all text to the file if the
user types more than 1000 characters.

So I guess you mean, that I should use a dynamic array so that I don't need
to have a fixed size of the buffer. That would make the user being able to enter
as many characters as he/she wanted.