How do I read user input and write it to a .txt. file?

I need to be able to prompt the user to input text, which is then taken and inputed into a text file. It then stops reading once the user enters CRTL-D/fputs returns NULL.

I can open a file and use fprintf to write to it, but now I need to write to the file using user input. I don't really know where to start.

I know how to read a .txt file and print its contents to the terminal using fputs, but writing to one through the terminal is too confusing for me...

int main(int argc, char *argv[]) {
FILE *f;

  f = fopen(argv[1], "w");
  if (errno) {
      perror("Error opening file.");
      exit(1);
  }

  fprintf(f, "Hello, Jake.\n");
  fclose(f);
}

I need a while loop that ends once the fputs or feof returns NULL.

If at any point I have said something that doesn't make sense, it's because I am confused. Learning C for uni is driving me nuts :(

Solution

You should create and open the file first. Then in a loop, start reading input with fgets(). In every iteration, write what you just read to the file. When the user inputs EOF, then close the file and you are done.

Example:

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

#define BUFFERSIZE 64

int main(void)
{

    FILE *fp;   /* File pointer*/
    char filename[] = "output.txt";

    /* Creating (open) a file*/
    fp = fopen(filename, "w");
    /* Check file created or not*/
    if(fp == NULL)
    {
        printf("File was not created!!!\n");
        exit(0); /* Exit from program*/
    }

    printf("File created successfully\n");
    /* Read from input */
    char buffer[BUFFERSIZE];
    while(fgets(buffer, BUFFERSIZE, stdin)) /* Break with ^D or ^Z */
    {
        /* Remove trailing newline */
        buffer[strcspn(buffer, "\n")] = 0;
        /* Writting into file*/
        fprintf(fp, "%s\n", buffer);
    }

    printf("Data written successfully.\n");
    fclose(fp);
    return 0;
}

Output:

Georgioss-MBP:gsamaras$ gcc main.c
Georgioss-MBP:gsamaras$ ./a.out 
File created successfully
Hello Stack Overflow
You are the best!
Data written successfully.
Georgioss-MBP:gsamaras$ cat output.txt 
Hello Stack Overflow
You are the best!

Note: I removed the newline fgets stores.