Thread: Help please

here's what I have now, it seems to work, but it might only appear that way. I need to make a file of all 0's to check it.

Code:

#include <stdlib.h>
#include <stdio.h>
main (int argc, char** argv )
{   int Key = atoi(argv[2]);
FILE *in, *out;
int ch = *argv[1];

if(Key > 255 || Key < 0)
{
 fprintf(stderr, "key must be between 0 and 255");
 return(EXIT_FAILURE);
}
if ( argc != 5 || (*argv[1] != 'e' && *argv[1] != 'd' && *argv[1] != 'E' && *argv[1] != 'D') )
{
fprintf( stderr, "only enter e to encipher or d to decipher\n");
return( EXIT_FAILURE );
}
/* Open the source file for "read binary" so that */
/* end of line characters are not translated */
if ( (in = fopen( argv[3], "rb")) == NULL )
{
perror( argv[3] );
return( EXIT_FAILURE );
}
/* Open the destination file for "write binary" */
if ( (out = fopen( argv[4], "wb")) == NULL )
{
perror( argv[4] );
return( EXIT_FAILURE );
}
/* Copy characters from input to output until end of file */
while ( (ch = fgetc(in)) != EOF )
{
 if(strcmp(argv[1], "e") == 0 || strcmp(argv[1], "E") == 0)
 {
 ch = (ch + Key) % 256;
 fputc( ch, out );
 Key++ % 256;
 }
 if(strcmp(argv[1], "d") == 0 || strcmp(argv[1], "D") == 0)
 {
 ch = (ch - Key) % 256;
 fputc( ch, out );
 Key++ % 256;
 }
}
/* Close the input and the output files */
if ( fclose( in ) == EOF )
{
perror( argv[1] );
return( EXIT_FAILURE );
}
if ( fclose( out ) == EOF )
{
perror( argv[2] );
return( EXIT_FAILURE );
}
return( EXIT_SUCCESS );
}

Its easier for us to (manually) check your code if you use whitespace and indent your code. Some people (including myself) wont look through the code if it looks like this, because its too easy to miss important details when its not formatted "properly".

sorry, I think I've made it better now:

Code:

#include <stdlib.h>
#include <stdio.h>
main (int argc, char** argv )
{   
 int Key = atoi(argv[2]);
 FILE *in, *out;
 int ch = *argv[1];

  if(Key > 255 || Key < 0)
  {
   fprintf(stderr, "key must be between 0 and 255");
   return(EXIT_FAILURE);
  }

  if ( argc != 5 || (*argv[1] != 'e' && *argv[1] != 'd' && *argv[1] != 'E' && *argv[1] != 'D') )
  {
   fprintf( stderr, "only enter e to encipher or d to decipher\n");
   return( EXIT_FAILURE );
  }

  if ( (in = fopen( argv[3], "rb")) == NULL )
  {
    perror( argv[3] );
    return( EXIT_FAILURE );
  }

  if ( (out = fopen( argv[4], "wb")) == NULL )
  {
    perror( argv[4] );
    return( EXIT_FAILURE );
  }

 while ( (ch = fgetc(in)) != EOF )
 {
   if(strcmp(argv[1], "e") == 0 || strcmp(argv[1], "E") == 0)
   {
     ch = (ch + Key) % 256;
     fputc( ch, out );
     Key++ % 256;
   }

   if(strcmp(argv[1], "d") == 0 || strcmp(argv[1], "D") == 0)
   {
     ch = (ch - Key) % 256;
     fputc( ch, out );
     Key++ % 256;
   }
 }

 if ( fclose( in ) == EOF )
 {
  perror( argv[1] );
  return( EXIT_FAILURE );
 }

 if ( fclose( out ) == EOF )
 {
   perror( argv[2] );
   return( EXIT_FAILURE );
 }

return( EXIT_SUCCESS );
}