how to Modify the hello.c program to open an input file read from the input file and write to another output file This program reads text from one file and writes to another file. code example

Example: how to create a file in c

/**
 * C program to create a file and write data into file.
 */

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

#define DATA_SIZE 1000

int main()
{
    /* Variable to store user content */
    char data[DATA_SIZE];

    /* File pointer to hold reference to our file */
    FILE * fPtr;


    /* 
     * Open file in w (write) mode. 
     * "data/file1.txt" is complete path to create file
     */
    fPtr = fopen("data/file1.txt", "w");


    /* fopen() return NULL if last operation was unsuccessful */
    if(fPtr == NULL)
    {
        /* File not created hence exit */
        printf("Unable to create file.\n");
        exit(EXIT_FAILURE);
    }


    /* Input contents from user to store in file */
    printf("Enter contents to store in file : \n");
    fgets(data, DATA_SIZE, stdin);


    /* Write data to file */
    fputs(data, fPtr);


    /* Close file to save file data */
    fclose(fPtr);


    /* Success message */
    printf("File created and saved successfully. :) \n");


    return 0;
}