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**Using data i read from . files**

May 12th, 2005

/*I used and modified a piece of code i found in here and my main(){} looks like this

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int main()
{
   HANDLE  hConsole;
   char welcome_l1[100];
   char welcome_l2[100];
   char welcome_l3[100];
   char welcome_l4[100];
   unsigned short k=120;
   hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
   ifstream file("ver");
   file.getline(welcome_l1, 100);
   file.getline(welcome_l2, 100);
   file.getline(welcome_l3, 100);
   file.getline(welcome_l4, 100);
   SetConsoleTextAttribute(hConsole, k);
   cout<<welcome_l1 <<"\n";
   cout<<welcome_l2 <<"\n";
   cout<<welcome_l3 <<"\n";
   cout<<welcome_l4 <<"\n";
   SetConsoleTextAttribute(hConsole, 8);
   return 0;
}
int main()
{
   HANDLE  hConsole;
   char welcome_l1[100];
   char welcome_l2[100];
   char welcome_l3[100];
   char welcome_l4[100];
   unsigned short k=120;
   hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
   ifstream file("ver");
   file.getline(welcome_l1, 100);
   file.getline(welcome_l2, 100);
   file.getline(welcome_l3, 100);
   file.getline(welcome_l4, 100);
   SetConsoleTextAttribute(hConsole, k);
   cout<<welcome_l1 <<"\n";
   cout<<welcome_l2 <<"\n";
   cout<<welcome_l3 <<"\n";
   cout<<welcome_l4 <<"\n";
   SetConsoleTextAttribute(hConsole, 8);
   return 0;
}

<< moderator edit: added [code][/code] tags and indented code >>

/*My -ver- file prints out the version of the program and the author. I have a big problem though if i want to use variables stored in files with differend extensions, like "*.rc" for example. I want my program to be extremely flexible, i dont want to recompile it 1000 times. So is anyone here able to suggest how to store && use (and why not modify) data from external files?
I want to mention that my program is and will not be commercial...*/

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subtronic

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Junior Poster

**Re: Using data i read from . files**

May 12th, 2005

http://www.busy-wait.com/

#include <fstream>  

using namespace std;

int main(int argc, char **argv)
{
        ifstream file;

        if (argc == 2) {
                file.open(argv[1]);
                .....
        }

        .....

        return 0;
}

Or something

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subtronic

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**Re: Using data i read from . files**

May 12th, 2005

Neat I wrote a little C program to format my DaniWeb example code, such that it is formatted in the Kerningham and Ritchie C-style tradition with 8-space tabs and 80 character columns. And to make it harder to just cut-and-paste code and to also add to the readability, line numbering with some sexy bbCode... and a useless timestamp for good measure

Generated: Thu May 12 14:35:27 2005

http://www.busy-wait.com/

[001]     #include <fstream>
[002]
[003]     using namespace std;
[004]
[005]     int main(int argc, char **argv)
[006]     {
[007]             ifstream file;
[008]
[009]             if (argc == 2) {
[010]                     file.open(argv[1]);
[011]                     /* ..... */
[012]             }
[013]
[014]             /* ..... */
[015]
[016]             return 0;
[017]     }

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Junior Poster in Training

**Re: Using data i read from . files**

May 17th, 2005

Thank you very much subtronic. Thank you for the reply, but, well... i cant really understand how i use it... i am quite confused, sorry, i am not that good to understand where exactly i put the name of the file i have to read?
And i dont understand why you put that (argc == 2)... :cry:

And one more thing; it must be quite simple: how can i read "10" characters, after "5" characters from the beggining of the line "3" of a text file?

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Dave Sinkula Dave Sinkula is offline

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long time no c

**Re: Using data i read from . files**

May 17th, 2005

•

Originally Posted by Prahaai

i cant really understand how i use it... i am quite confused, sorry, i am not that good to understand where exactly i put the name of the file i have to read?
And i dont understand why you put that (argc == 2)... :cry:

From the command line.

#include <iostream>

int main(int argc, char *argv[])
{
   int i;
   for (i = 1; i < argc; ++i)
   {
      std::cout << "argv[" << i << "] = \"" << argv[i] << "\"\n";
   }
   return 0;
}

/* my output
C:\Test>testpp filename
argv[1] = "filename"
*/

•

Originally Posted by Prahaai

And one more thing; it must be quite simple: how can i read "10" characters, after "5" characters from the beggining of the line "3" of a text file?

Maybe like this.

#include <iostream>
#include <fstream>
#include <string>

int main(int argc, char *argv[])
{
   if ( argc > 1 )
   {
      std::ifstream file(argv[1]);
      std::string   line;
      if ( getline(file, line) && /* read and discard line 1 */
           getline(file, line) && /* read and discard line 2 */
           getline(file, line) )  /* read line 3 */
      {
         std::cout << line.substr(5, 10) << std::endl;
      }
   }
   return 0;
}

/* my output
C:\Test>testpp testpp.cpp
ude <strin
*/

"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand

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Join Date: May 2005

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**Re: Using data i read from . files**

May 20th, 2005

Dear "Dave Sinkula", i cant stop wondering how did that code magically compile... I dont understand anything of it... i am probably much more a noob than i thought.
I wanted to use your function as an external, NON-main function, so that i will be able to call from any other function. Of course, i failed...

Anyway, the function you gave me has constant values in

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std::cout << line.substr(5, 10) << std::endl;
std::cout << line.substr(5, 10) << std::endl;

so it is too inflexible.

Can you, or anyone else help me read "NoCharsWanted" characters after "NoCharsIgnored" ignored characters, after "NoLinesIgnored" ignored lines (assuming that the characters i need are on the same line, i mean, i only want to read from one line), from MyFile.txt file?

And there is another problem i have: how can i do the exact same thing, but with INTEGERS? I want to read a few integers from a file...
Thank you very much.

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Dogtree

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**Re: Using data i read from . files**

May 20th, 2005

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int NoLinesIgnored, NoCharsIgnored, NoCharsWanted;
std::string s;
 
// ...
 
while (--NoLinesIgnored >= 0) {
  // Read and discard a line
  file.ignore(std::numeric_limits<streamsize>::max(), '\n');
}
 
// Read and discard N characters
file.ignore(NoCharsIgnored);
 
// Read and save N characters
file >> std::setw(NoCharsWanted) >> s;
int NoLinesIgnored, NoCharsIgnored, NoCharsWanted;
std::string s;

// ...

while (--NoLinesIgnored >= 0) {
  // Read and discard a line
  file.ignore(std::numeric_limits<streamsize>::max(), '\n');
}

// Read and discard N characters
file.ignore(NoCharsIgnored);

// Read and save N characters
file >> std::setw(NoCharsWanted) >> s;

How you do this will vary depending on your whitespace needs, but the above should suffice. Concerning integers, can you be more specific about what you want to do? What does the file look like, how do you want to process it, and what should the output be?

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long time no c

**Re: Using data i read from . files**

May 20th, 2005

#include <iostream>
#include <fstream>
#include <string>

std::string foo(const char *filename,
                int NoCharsWanted, int NoCharsIgnored, int NoLinesIgnored)
{
   std::ifstream file(filename);
   std::string   line;
   for ( int i = 0; i < NoLinesIgnored; ++i )
   {
      if ( !getline(file, line) )
      {
         return "";
      }
   }
   return line.substr(NoCharsIgnored, NoCharsWanted);
}

int main()
{
   std::string text = foo(__FILE__, 10, 5, 3);
   std::cout << text << std::endl;
   return 0;
}

/* my output
ude <strin
*/

•

And there is another problem i have: how can i do the exact same thing, but with INTEGERS?

[Of course. It always seems that finding the question is more difficult than finding the answer when you're starting out.]

How about posting a small sample of a file that you are trying to parse. Then describe the input and output you would like.

Last edited by Dave Sinkula; May 20th, 2005 at 3:49 pm. Reason: D'oh! Pokey and of lesser quality.

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