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#include <stdio.h>
#include <ctype.h>  /* for isgraph() */

#define LINESIZE 16

void hd(FILE *in, FILE *out);
void print(FILE *fp,long addr,unsigned char *buf,int len);

int main(int argc, char *argv[])
{
  int err = 0; /* returning no-zero on case of open error */

  if ( argc < 2 )
  {
    hd( stdin, stdout);  /* no command line argument */
  }
  else
  {
    int i;
    for ( i = 1; i < argc; ++i )   /* the file arguments */
    {
      FILE *fp = fopen( argv[i], "r");
      if ( NULL != fp )  /* open successful */
      {
        hd( fp, stdout);
        fclose( fp);  /* only fix number of opened files */
      }
      else
      {      
        fprintf( stderr, "Can't open %s\n", argv[i]);
        err = 1;    /* at least one file open error */
      }
    }
  }
  return err;  /* 0 == ok, 1 == error(s) */
}

void hd( FILE *in, FILE *out)  /* for future improvement */
{
  char ch;
  unsigned char buffer[LINESIZE];/* %x requires unsigned */
  int cnt = 0;
  long addr = 0L;  /* address inside the file */

  while ( EOF != (ch = fgetc(in)) )
  {
    buffer[cnt++] = ch;
    if ( LINESIZE == cnt )  /* buffer full */
    {
      print( out, addr, buffer, cnt); /* print buffer */
      addr += cnt;   /* == BUFSIZE, increment address */
      cnt = 0;
    }
  }
  /* if there are char(s) in buffer when EOF has occurs  
     we have to print them too                          */
  if ( cnt > 0 )
  {
    print( out, addr, buffer, cnt);  
  }
}

void print(FILE *out,long addr,unsigned char *buf,int len)
{
  int i;
  fprintf( out, "%08lx  |  ", addr);  /* address in hexa */
  for ( i = 0; i < len; ++i )
  {
    fprintf( out, " %02x", buf[i]);  /* a char in hexa */
  }
  for ( ; i < LINESIZE; ++i)  /* spaces for last line */
  {
    fprintf( out, "   ");
  }
  fprintf( out, "  |  ");
  for ( i = 0; i < len; ++i)      /* the chars or '.' */
  {  
    fprintf( out, "%c", isgraph(buf[i]) ? buf[i] : '.');
  }
  fprintf( out, "\n");   /* very end of printed line */
}