Programming Forums > Application Development > C++

starbeam · Feb 21st, 2008, 9:30 PM

I am working on this program that is a hex dump. I have to use a file. I have it where it ask the user what file it is and they enter like test.txt and it opens and uses file test but I want to change it so that it does not ask the user. How would I do that. Here is what I have.

 c++ Syntax (Toggle Plain Text) 
if ( argc <= 1 ) 
  {
    cout << "\n";
    cout << "HEXDUMP:\n";
    cout << "  Please enter the name of a file to be analyzed.\n";
 
    cin.getline ( file_in_name, sizeof ( file_in_name ) );
 
    handle ( file_in_name );
  }
if ( argc <= 1 ) 
  {
    cout << "\n";
    cout << "HEXDUMP:\n";
    cout << "  Please enter the name of a file to be analyzed.\n";

    cin.getline ( file_in_name, sizeof ( file_in_name ) );

    handle ( file_in_name );
  }

Ancient Dragon · Feb 21st, 2008, 9:35 PM

delete lines 5, 6 and 7 then set file_in_name to whatever you want
file_in_name = "test.txt";

starbeam · Feb 21st, 2008, 9:43 PM

Now it is giving me an error.....c:\Documents and Settings\Owner\Desktop\program2\program2.cpp(32) : error C2440: '=' : cannot convert from 'const char [11]' to 'char [80]'

 C++ Syntax (Toggle Plain Text) 
int main ( long argc, char *argv[] )
 
 
{
  char file_in_name[80];
  int i;
 
 
  if ( argc <= 1 ) 
  {
    cout << "\n";
    cout << "HEXDUMP:\n";
 //   cout << "  Please enter the name of a file to be analyzed.\n";
	file_in_name = "test.txt";
   // cin.getline ( file_in_name, sizeof ( file_in_name ) );
 
    handle ( file_in_name );
  }
int main ( long argc, char *argv[] )


{
  char file_in_name[80];
  int i;


  if ( argc <= 1 ) 
  {
    cout << "\n";
    cout << "HEXDUMP:\n";
 //   cout << "  Please enter the name of a file to be analyzed.\n";
	file_in_name = "test.txt";
   // cin.getline ( file_in_name, sizeof ( file_in_name ) );

    handle ( file_in_name );
  }

Sane · Feb 21st, 2008, 10:34 PM

This is what Ancient Dragon was telling you to do:

 CPP Syntax (Toggle Plain Text) 
int main ( long argc, char *argv[] )
 
 
{
  char file_in_name[80];
  int i;
 
 
  if ( argc <= 1 ) 
  {
    cout << "\n";
    cout << "HEXDUMP:\n";
    // cout << "  Please enter the name of a file to be analyzed.\n";
 
    // cin.getline ( file_in_name, sizeof ( file_in_name ) );
 
    handle ( "test.txt" );
 
}
int main ( long argc, char *argv[] )


{
  char file_in_name[80];
  int i;


  if ( argc <= 1 ) 
  {
    cout << "\n";
    cout << "HEXDUMP:\n";
    // cout << "  Please enter the name of a file to be analyzed.\n";

    // cin.getline ( file_in_name, sizeof ( file_in_name ) );

    handle ( "test.txt" );

}

starbeam · Feb 21st, 2008, 10:57 PM

thanks that helped

Ooble · Feb 21st, 2008, 11:27 PM

In C and C++, you can't assign an array to another array: you have to individually copy each element of the array from one to another. As a C-style string (which is what you're using) is simply an array of characters, you can't do this:

(Toggle Plain Text)

file_in_name = "test.txt";

Instead, you have to do this:

(Toggle Plain Text)

strncpy(file_in_name, "test.txt", 79);

You may have been confused because the first way of doing this is allowed when you declare the variable. It's a quirk of C - you can only do it then.

Feb 21st, 2008, 9:30 PM	#1
starbeam Newbie Join Date: Jan 2008 Posts: 10 Rep Power: 0	Help with a file I am working on this program that is a hex dump. I have to use a file. I have it where it ask the user what file it is and they enter like test.txt and it opens and uses file test but I want to change it so that it does not ask the user. How would I do that. Here is what I have. c++ Syntax (Toggle Plain Text) if ( argc <= 1 ) { cout << "\n"; cout << "HEXDUMP:\n"; cout << " Please enter the name of a file to be analyzed.\n"; cin.getline ( file_in_name, sizeof ( file_in_name ) ); handle ( file_in_name ); } if ( argc <= 1 ) { cout << "\n"; cout << "HEXDUMP:\n"; cout << " Please enter the name of a file to be analyzed.\n"; cin.getline ( file_in_name, sizeof ( file_in_name ) ); handle ( file_in_name ); }

Feb 21st, 2008, 9:35 PM	#2
Ancient Dragon PFO God In Training Join Date: Jun 2005 Location: near St Louis, MO. (USA) Posts: 546 Rep Power: 4	Re: Help with a file delete lines 5, 6 and 7 then set file_in_name to whatever you want `file_in_name = "test.txt";`

Feb 21st, 2008, 9:43 PM	#3
starbeam Newbie Join Date: Jan 2008 Posts: 10 Rep Power: 0	Re: Help with a file Now it is giving me an error.....c:\Documents and Settings\Owner\Desktop\program2\program2.cpp(32) : error C2440: '=' : cannot convert from 'const char [11]' to 'char [80]' C++ Syntax (Toggle Plain Text) int main ( long argc, char argv[] ) { char file_in_name[80]; int i; if ( argc <= 1 ) { cout << "\n"; cout << "HEXDUMP:\n"; // cout << " Please enter the name of a file to be analyzed.\n"; file_in_name = "test.txt"; // cin.getline ( file_in_name, sizeof ( file_in_name ) ); handle ( file_in_name ); } int main ( long argc, char argv[] ) { char file_in_name[80]; int i; if ( argc <= 1 ) { cout << "\n"; cout << "HEXDUMP:\n"; // cout << " Please enter the name of a file to be analyzed.\n"; file_in_name = "test.txt"; // cin.getline ( file_in_name, sizeof ( file_in_name ) ); handle ( file_in_name ); }

Feb 21st, 2008, 10:34 PM	#4
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 1,885 Rep Power: 5	Re: Help with a file This is what Ancient Dragon was telling you to do: CPP Syntax (Toggle Plain Text) int main ( long argc, char argv[] ) { char file_in_name[80]; int i; if ( argc <= 1 ) { cout << "\n"; cout << "HEXDUMP:\n"; // cout << " Please enter the name of a file to be analyzed.\n"; // cin.getline ( file_in_name, sizeof ( file_in_name ) ); handle ( "test.txt" ); } int main ( long argc, char argv[] ) { char file_in_name[80]; int i; if ( argc <= 1 ) { cout << "\n"; cout << "HEXDUMP:\n"; // cout << " Please enter the name of a file to be analyzed.\n"; // cin.getline ( file_in_name, sizeof ( file_in_name ) ); handle ( "test.txt" ); } __________________ Waterloo's Canadian Computing Competition (CCC) - Stage 2 Problems, Solutions, and Test Data

Feb 21st, 2008, 10:57 PM	#5
starbeam Newbie Join Date: Jan 2008 Posts: 10 Rep Power: 0	Re: Help with a file thanks that helped

Feb 21st, 2008, 11:27 PM	#6
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Re: Help with a file In C and C++, you can't assign an array to another array: you have to individually copy each element of the array from one to another. As a C-style string (which is what you're using) is simply an array of characters, you can't do this: (Toggle Plain Text) file_in_name = "test.txt"; file_in_name = "test.txt"; Instead, you have to do this: (Toggle Plain Text) strncpy(file_in_name, "test.txt", 79); strncpy(file_in_name, "test.txt", 79); You may have been confused because the first way of doing this is allowed when you declare the variable. It's a quirk of C - you can only do it then. __________________ Me :: You :: Them

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Programming Forums > Application Development > C++

Help with a file