Reading reads strings from keyboard and writing them to a file - c

Question

Here's my task and below you can find my specific question and the code I wrote:
Write a program that reads strings and writes them to a file. The string must be dynamically
allocated and the string can be of arbitrary length. When the string has been read it is written to the
file. The length of the string must be written first then a colon (‘:’) and then the string. The program
stops when user enters a single dot (‘.’) on the line.
For example:
User enters: This is a test
Program writes to file: 14:This is a test
Question:
My code adds the number of characters and the colon, but not the string I typed, and when entered "." it wont exit
This is the code I have so far:
#pragma warning(disable: 4996)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_NAME_SZ 256
int main() {
char key[] = ".";
char *text;
int i;
text = (char*)malloc(MAX_NAME_SZ);
FILE* fp;
do {
printf("Enter text or '.' to exit: ", text);
fgets(text, MAX_NAME_SZ, stdin);
for (i = 0; text[i] != '\0'; ++i);
printf("%d: %s", i);
fp = fopen("EX13.txt", "w");
while ((text = getchar()) != EOF) {
putc(text, fp);
}
fclose(fp);
printf("%s\n", text);
} while (strncmp(key, text, 1) != 0);
puts("Exit program");
free(text);
return 0;
}

Answer 1

There are many issues in your code, almost everything is wrong.
Just a few problems:
You use printf("%d: %s", i); to print on the screen what should go into the file.
The loop while ((text = getchar()) != EOF) doesn't make any sense.
You're closing the file after the first line entered
You ignore all compiler warnings
The end condition while (strncmp(key, text, 1) != 0) is wrong, you're only testing if the string starts with a ., and you're testing it too late.
This could be a start:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_NAME_SZ 256
int main() {
char* text;
int i;
text = (char*)malloc(MAX_NAME_SZ);
FILE* fp;
fp = fopen("EX13.txt", "w");
if (fp == NULL)
{
printf("Can't open file\n");
exit(1);
}
do {
printf("Enter text or '.' to exit: ");
fgets(text, MAX_NAME_SZ, stdin);
if (strcmp(".\n", text) == 0)
break;
for (i = 0; text[i] != '\0' && text[i] != '\n'; ++i);
fprintf(fp, "%d: %s", i, text);
} while (1);
fclose(fp);
puts("Exit program");
free(text);
return 0;
}
There is a limitation though, in this program the maximum line length is 254 characters, not including the newline character. As far as I understood, the line length must be arbitrary.
I let you do this on your own as an exercise, but at your C knowledge level it will be hard.

Answer 2

I think this should work for strings that are shorter than 255 chars.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_NAME_SZ 256
int main()
{
char key[] = ".\n";
char *text;
text = (char*)malloc(MAX_NAME_SZ);
if (text == NULL)
{
perror("problem with allocating memory with malloc for *text");
return 1;
}
FILE *fp;
fp = fopen("EX13.txt", "w");
if (fp == NULL)
{
perror("EX13.txt not opened.\n");
return 1;
}
printf("Enter text or '.' to exit: ");
while (fgets(text, MAX_NAME_SZ, stdin) && strcmp(key, text))
{
fprintf(fp, "%ld: %s", strlen(text) - 1, text);
printf("Enter text or '.' to exit: ");
}
free((void *) text);
fclose(fp);
puts("Exit program");
return 0;
}