Answer to Question 33C-1

// Usage: copy A B
// Create a copy of file A called B.

#include <cstdio>
using namespace std;

//========================================================
//                    copy
//========================================================
// copy(oldf,newf) copies all of file oldf into file newf.
//
// Requirement: oldf must have been opened for reading and
// newf must have been opened for writing.
//
// Note: This function does not close oldf or newf.
// It just does the copy.
//========================================================

void copy(FILE* oldf, FILE* newf)
{
  int c = getc(oldf);
  while(c != EOF)
  {
    putc(c, newf);
    c = getc(oldf);
  }
}

//========================================================
//                    openInfile
//========================================================
// Open 'fileName' for reading and return the open file.
// If 'fileName' cannot be opened, print a message and
// return NULL.
//========================================================

FILE* openInfile(const char* fileName)
{
  FILE* inf = fopen(fileName, "r");

  if(inf == NULL)
  {
    printf("Cannot open file %s for reading\n", fileName);
    return NULL;
  }  
  return inf;
}

//========================================================
//                    openOutfile
//========================================================
// Open 'fileName' for writing and return the open file.
// If 'fileName' cannot be opened, print a message and
// return NULL.
//========================================================

FILE* openOutfile(const char* fileName)
{
  FILE* outf = fopen(fileName, "w");
 
  if(outf == NULL)
  {
    printf("Cannot open file %s for writing\n", fileName);
    return NULL;
  }
  return outf;
}

//========================================================
//                    main
//========================================================

int main(int argc, char* argv[])
{
  if(argc == 3)
  {
    //---------------
    // Open inf.
    //---------------

    FILE* inf = openInfile(argv[1]);
    if(inf == NULL)
    {
      return 1;
    }

    //---------------
    // Open outf.
    //---------------

    FILE* outf = openOutfile(argv[2]);
    if(outf == NULL)
    {
      fclose(inf);
      return 1;
    }

    //---------------
    // Do the copy.
    //---------------

    copy(inf, outf);
    fclose(inf);
    fclose(outf);
    return 0;
  }

  else // wrong number of command-line arguments
  {
    printf("usage: copy old new\n");
    return 1;
  }
}