2010-02-03 |  TestNameTR  | Viewed: 742  |    1

Writing to Files Using fwrite

This function has the same four arguments to fread:

The first is a char * variable and is what you want to write into a file.

The second is the size of char, i.e. 1.

The third is the number of characters to write - this does come into effect when passing a char * as opposed to a char array.

Finally, the last argument is the FILE pointer to the file to write to.

This example is saved as file.c - it opens file.c for reading, and copies the content into file2.c

Afterwards, it'll open file2.c and display the source code on the screen, including the comments!

Notice I used two FILE pointers - one for the reading, the other for the writing.

#include <stdio.h>

int main() {
  FILE *sourceFile;
  FILE *destinationFile;
  char *buffer;
  int n;

  sourceFile = fopen("file.c", "r");
  destinationFile = fopen("file2.c", "w");

  if(sourceFile==NULL) {
    printf("Error: can't access file.c.\n");
    return 1;
  }
  else if(destinationFile==NULL) {
    printf("Error: can't create file for writing.\n");
    return 1;
  }
  else {
    n = fread(buffer, 1, 1000, sourceFile); /* grab all the text */
    fwrite(buffer, 1, n, destinationFile);  /* put it in file2.c */
    fclose(sourceFile);
    fclose(destinationFile);

    destinationFile = fopen("file2.c", "r");
    n = fread(buffer, 1, 1000, destinationFile); /* read file2.c   */
    printf("%s", buffer);                        /* display it all */

    fclose(destinationFile);
    return 0;
  }
}

Reference link:
http://irc.essex.ac.uk/www.iota-six.co.uk/c/i4_fwrite_fscanf_fprintf.asp