/*
** $Id: files.c 776 2008-02-16 01:38:17Z phf $
**
** Here's a mess of code we used in lecture to look at the
** basics of files in C. I simply added some comments, you
** can find better explanations in the K&R book as well as
** the stdio man page.
*/

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

#define SIZE 1024

int main(void)
{
  puts( "File stuff... :-)" );

  /*
  ** First an example that essentially is cat on
  ** a file, our own source code in this case. I
  ** had this as the only example in lecture in
  ** Spring 2008, that's why I had all those
  ** exit codes in there. Just commented out to
  ** also run the rest of this demo. :-)
  */
  FILE *me = fopen("files.c", "r");
  if (me != NULL) {
    puts("files: yeah, found and then opened myself for reading!");

    // this is the "cat" like loop, now using
    // specific file pointers
    int c;
    while ((c = fgetc(me)) != EOF) {
      fputc(c, stdout);
    }

    int res = fclose(me);
    if (res == EOF) {
      puts("files: can't get rid of myself (well, my own source code)!");
      // return EXIT_FAILURE;
    }
    // return EXIT_SUCCESS;
  }
  else {
    puts("files: can't find myself (well, my own source code)!");
    // return EXIT_FAILURE;
  }

  /*
  ** Now we'll use fgets() to read "line by line" or
  ** some approximation thereof.
  */

  /* A buffer we'll use for input and output. */
  char buffer[SIZE];

  /* You can open a file for reading this way. */
  FILE *file = fopen( "files.c", "r" );

  /* You need to check if the file could be opened. */
  if (file != NULL) {
    puts( "Opened the file!" );

    /* You can use ftell() to see where you are in a file. */
    printf( "Pos: %ld", ftell( file ) );

    /* Using fgets() you can read a line up to a maximum size. */
    while (fgets( buffer, 1024, file ) != NULL) {
      printf( "%s", buffer );
      printf( "Pos: %ld", ftell( file ) );
    }

    /* When fgets() returns NULL we reached the end of the file. */
    /* We still need to close the file though! */
    fclose( file );

    puts( "Closed the file!" );
  }
  else {
    puts( "File not found!" );
  }

  /*
  ** You can open a file for writing this way. If it already
  ** exists, it will be "truncated" and you'll "lose" whatever
  ** was in it before. (In lecture we did "a" for append as
  ** well.)
  */
  file = fopen( "test-file", "w" );
  if (file != NULL) {
    puts( "File created!" );

    /* You can write stuff to the file of course. */
    fputs( "Habeas Corpus sure was nice...", file );

    /* Close it! */
    fclose( file );

    puts( "File closed!" );
  }
  else {
    puts( "Can't create file!" );
  }

  /*
  ** You can open a file for writing this way without losing
  ** data. Yes, confusing...
  */
  file = fopen( "test-file", "r+" );
  if (file != NULL) {
    puts( "File opened!" );
    /* You can go to an arbitrary position in the file. */
    fseek( file, 1024, SEEK_SET );
    /* And you can write stuff to the file of course. */
    fputs( "AT 1024!", file );
    /* What thou fopenst thou shallst fclose! :-) */
    fclose( file );
    puts( "File closed!" );
  }
  else {
    puts( "Can't create file!" );
  }

  return EXIT_SUCCESS;
}