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File array question

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Jon182

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File array question

Dec 22nd, 2005

Hey guys,

I have the following code, but for some reason it does not work with bigger txt files is this because of the size of the array?

And if so is there a simple way to solve the problem?

Thanks in advance for any help.

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char ch[1000];
int v_word = 0;
int c_word = 0;
ifstream file("c:/test.txt");
 
   if (file.is_open()) 
     {
	while (file.getline(ch, 1000))
		if(strcmp(ch, "int") == 0)
		  v_word++;
 
     }
 
cout<<v_word<<endl;
cout<<c_word<<endl;
file.close();
char ch[1000];
int v_word = 0;
int c_word = 0;
ifstream file("c:/test.txt");

   if (file.is_open()) 
     {
	while (file.getline(ch, 1000))
		if(strcmp(ch, "int") == 0)
		  v_word++;
		
     }
	
cout<<v_word<<endl;
cout<<c_word<<endl;
file.close();

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Join Date: Aug 2005

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Ancient Dragon Ancient Dragon is offline

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Re: File array question

Dec 22nd, 2005

it should work with text files of any size. Are any lines longer than 1,000 bytes? What is the purpose of checking if one of the lines = "int" ? Is there anything else following "int" on that line?

This is a c++ program -- why don't you use std::string instead of c-style arrays?

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 C++ Syntax (Toggle Plain Text) 
#include <string>
...
std::string line;
int v_word = 0;
int c_word = 0;
int spot;
ifstream file("c:/test.txt");
 
   if (file.is_open()) 
     {
	while (getline(fin,line) )
		if( (spot = line.find("int")) >= 0)
		  v_word++;
     }
#include <string>
...
std::string line;
int v_word = 0;
int c_word = 0;
int spot;
ifstream file("c:/test.txt");

   if (file.is_open()) 
     {
	while (getline(fin,line) )
		if( (spot = line.find("int")) >= 0)
		  v_word++;
     }

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Jon182

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Re: File array question

Dec 22nd, 2005

Hi thanks for your reply, The purpose of the int was just so i could count how many times it appears in the file it my full version also searches for other words. Could this be why it doesn't work on larger files?
I will look into strings.

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Ancient Dragon Ancient Dragon is offline

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Re: File array question

Dec 22nd, 2005

what do you mean by "it doesn't work"? what doesn't work? strcmp() compares the entire line with the text you put in literals, in your example it is "int". So if the line is "int some more stuff here", then strcmp() will fail. If you only want the first three characters, the use strncmp(), or if "int" can appear anywhere in the line use strstr(). Also you have to be careful with the comparison because strstr() will also find "intabc" is the same as "abcintabc" and " int ". So if strstr() finds the text "int" the program should check for space character immediately before and after. If there is no white space before and after, then strstr() did not find a word.

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Jon182

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Re: File array question

Dec 22nd, 2005

Hi thanks for your reply. I have tried to use strstr() but I keep getting the wrong word count.

For example all the txt file contains is "hello james" and it gives the count 0 for both words.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
	ifstream file("c:\\test.txt");
 
	if (file.is_open()) {
		while (file.getline(ch, 10000))
		{
			if(strstr(ch, "hello") == 0)
				v_word++;
 
			if(strstr(ch, "james") == 0)
				c_word++;
		}
	}
	ifstream file("c:\\test.txt");

	if (file.is_open()) {
		while (file.getline(ch, 10000))
		{
			if(strstr(ch, "hello") == 0)
				v_word++;

			if(strstr(ch, "james") == 0)
				c_word++;
		}
	}

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Dave Sinkula Dave Sinkula is offline

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long time no c

Re: File array question

Dec 22nd, 2005

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if(strstr(ch, "hello") == 0)
if(strstr(ch, "hello") == 0)

The return value of strstr is a pointer to the match or a NULL pointer when no match was found. Here you are checking for a NULL pointer, meaning when no match was found, so you would be incrementing your counter at the wrong time.

Try this to find at least one occurence per line.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if(strstr(ch, "hello") != 0)
if(strstr(ch, "hello") != 0)

"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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Jon182

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Re: File array question

Dec 22nd, 2005

Hi Dave, Thank you for your reply.

Is what you said also true for the strcmp() function?

Thanks.

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Re: File array question

Dec 22nd, 2005

strcmp() return 0 if the comparison succeed, or non-zero if it fails.

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Jon182

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Re: File array question

Dec 22nd, 2005

That what I thought but when I was tesing it if I used the code:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if(strcmp(ch, "hello") == 0)
if(strcmp(ch, "hello") == 0)

I got the wrong number of times the word occured.

but if I used the following code for strcmp()

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if(strcmp(ch, "hello") != 0)
if(strcmp(ch, "hello") != 0)

it works. But with strcmp() shouldn't it have worked with the first piece of code?

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Dave Sinkula Dave Sinkula is offline

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long time no c

Re: File array question

#10

Dec 22nd, 2005

If the whole line is just "hello", then doing a strcmp against "hello" will be 0. Otherwise it won't be ("hello james" is not the same as "hello").

Even with strstr, you may want to move down the string after a match. Consider an input file like this:

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C++ Syntax (Toggle Plain Text)

hello james hello james hello hello hello james james hello james

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
 
int main()
{
   char ch[1000];
   int v_word = 0;
   int c_word = 0;
   ifstream file("test.txt");
 
   if ( file.is_open() )
   {
      while ( file.getline(ch, 10000) )
      {
         char *match = ch;
         cout << "ch : " << ch << '\n';
         while ( (match = strstr(match, "hello")) != 0 )
         {
            cout << "<<hello>> " << match << '\n';
            v_word++;
            match += 5; /* the length of "hello" */
         }
 
         match = ch;
         while ( (match = strstr(match, "james")) != 0 )
         {
            cout << "<<james>> " << match << '\n';
            c_word++;
            match += 5; /* the length of "james" */
         }
      }
   }
 
   cout<<v_word<<endl;
   cout<<c_word<<endl;
   file.close();
   return 0;
}
 
/* my output
ch : hello james hello james hello hello hello james james hello james
<<hello>> hello james hello james hello hello hello james james hello james
<<hello>> hello james hello hello hello james james hello james
<<hello>> hello hello hello james james hello james
<<hello>> hello hello james james hello james
<<hello>> hello james james hello james
<<hello>> hello james
<<james>> james hello james hello hello hello james james hello james
<<james>> james hello hello hello james james hello james
<<james>> james james hello james
<<james>> james hello james
<<james>> james
6
5
*/
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;

int main()
{
   char ch[1000];
   int v_word = 0;
   int c_word = 0;
   ifstream file("test.txt");

   if ( file.is_open() )
   {
      while ( file.getline(ch, 10000) )
      {
         char *match = ch;
         cout << "ch : " << ch << '\n';
         while ( (match = strstr(match, "hello")) != 0 )
         {
            cout << "<<hello>> " << match << '\n';
            v_word++;
            match += 5; /* the length of "hello" */
         }

         match = ch;
         while ( (match = strstr(match, "james")) != 0 )
         {
            cout << "<<james>> " << match << '\n';
            c_word++;
            match += 5; /* the length of "james" */
         }
      }
   }

   cout<<v_word<<endl;
   cout<<c_word<<endl;
   file.close();
   return 0;
}

/* my output
ch : hello james hello james hello hello hello james james hello james
<<hello>> hello james hello james hello hello hello james james hello james
<<hello>> hello james hello hello hello james james hello james
<<hello>> hello hello hello james james hello james
<<hello>> hello hello james james hello james
<<hello>> hello james james hello james
<<hello>> hello james
<<james>> james hello james hello hello hello james james hello james
<<james>> james hello hello hello james james hello james
<<james>> james james hello james
<<james>> james hello james
<<james>> james
6
5
*/