/* Adapted from the book 'C by Dissection' by Kelly and Pohl */
#include <stdio.h>
#include <stdlib.h>

void   double_space(FILE *ifp, FILE *ofp);
void   prn_info(char *pgm_name);

int main(int argc, char **argv)
{
   FILE   *ifp, *ofp;

   if (argc != 3) {
      prn_info(argv[0]);
      exit(1);
   }
   ifp = fopen(argv[1], "r");             /* open for reading */
   ofp = fopen(argv[2], "w");             /* open for writing */
   double_space(ifp, ofp);
   fclose(ifp);
   fclose(ofp);
   return 0;
}

void  double_space(FILE *ifp, FILE *ofp)
{
   int  c;

   while ((c = fgetc(ifp)) != EOF) {
      fputc(c, ofp);
      if (c == '\n') fputc('\n', ofp);    /* duplicate newline */
   }
}  

void prn_info(char *pgm_name)
{
   printf("\n%s%s%s\n\n%s%s\n\n",
      "Usage:  ", pgm_name, "  infile  outfile",
      "The contents of infile will be double-spaced ",
      "and written to outfile.");
}