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Oct 9th, 2007

search in text file

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Hi am trying to make a simple application that write and read from and to a text file the problem is that i want to be able to aerch in the text file for an specific line.

the text file is a list of words with a meaning each word, the application ask for what word to search and i want to cout<< the specific line containing that word..

could someone can help me ??

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reaven

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Oct 9th, 2007

Re: search in text file

yes -- read each line sequentiall from star to finish until you get the line you want. use fstream's getline() to read an entire line then check only the first word to see if the line is the one you want.

Don't attempt to code all of that at one time. First get your program to open the file for reading. After that is code and compiles without error, add a loop using getline() to read each line. Get that working then code the next part.

Last edited by Ancient Dragon; Oct 9th, 2007 at 9:49 pm.

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Oct 10th, 2007

Re: search in text file

ok this is what i got

C++ Syntax (Toggle Plain Text)
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
 
int main()
{
	string line;
	char word;
 
	fstream dict("c://example.txt",ios::in);
 
	if (!dict.is_open()){ 
		cout << "Unable to open file";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;
	while(getline(dict,line)) 
		cout<<line<<"\n";
 
 
	return 0;
}
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
	string line;
	char word;
	
	fstream dict("c://example.txt",ios::in);

	if (!dict.is_open()){ 
		cout << "Unable to open file";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;
	while(getline(dict,line)) 
		cout<<line<<"\n";
		

	return 0;
}

this is the part i know, now what ?

thanks in advanced !!

reaven

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Oct 10th, 2007

Re: search in text file

expand the while loop to extract the first word (hint: use string's find() method to locate the first space), then compare that with the string that you entered from the command line. If they are the same then you can stop that loop.

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Oct 10th, 2007

Re: search in text file

C++ Syntax (Toggle Plain Text)
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
 
int main()
{
	string line;
	char* word="";
	size_t i;
	fstream dict("c://example.txt",ios::in);
 
	if (!dict.is_open()){ 
		cout << "Unable to open file \n";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;
 
	while(getline(dict,line))
        i = line.find(word);
 
        if (line.compare(word) != 0){
               cout << "result " <<line << endl;
 
      }else
 
		cout<<"Not in list"<<"\n";
 
 
	return 0;
}
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
	string line;
	char* word="";
	size_t i;
	fstream dict("c://example.txt",ios::in);

	if (!dict.is_open()){ 
		cout << "Unable to open file \n";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;

	while(getline(dict,line))
        i = line.find(word);
       
        if (line.compare(word) != 0){
               cout << "result " <<line << endl;

      }else

		cout<<"Not in list"<<"\n";
		

	return 0;
}

I have the idea of what you are saying but dont know how to put it in code

reaven

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Oct 10th, 2007

Re: search in text file

A little off. First you need to put braces around that entire while statement. Next, the find mentiond returns string::npos if the word is not found. You need to add a check to see if the find method worked or not.

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Oct 10th, 2007

Re: search in text file

C++ Syntax (Toggle Plain Text)
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
 
int main()
{
	string line;
	char* word="";
	size_t i;
	fstream dict("c://example.txt",ios::in);
 
	if (!dict.is_open()){ 
		cout << "Unable to open file \n";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;
	{
	while(getline(dict,line))   //read line by line
	i = line.find(word);    //try to find the var word in the string line an assign it to i
 
	if (i!=string::npos)      // dont exactly know what it does
  cout<<i<<" not found";      
	else 
		line.compare(word) != 0;  //compare the string line to the var word 
    cout << "result " <<line << endl;
	exit (1);
 
}
 
	return 0;
}
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
	string line;
	char* word="";
	size_t i;
	fstream dict("c://example.txt",ios::in);

	if (!dict.is_open()){ 
		cout << "Unable to open file \n";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;
	{
	while(getline(dict,line))   //read line by line
	i = line.find(word);    //try to find the var word in the string line an assign it to i
	
	if (i!=string::npos)      // dont exactly know what it does
  cout<<i<<" not found";      
	else 
		line.compare(word) != 0;  //compare the string line to the var word 
    cout << "result " <<line << endl;
	exit (1);
  
}

	return 0;
}

I know youre trying to make me understand but am a little lost here really !!
i put comments around the lines to see if i understand what each does correctly , please correct me if am wrong..

thanks a lot

reaven

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Oct 10th, 2007

Re: search in text file

Why not try a trivial example first without reading a text file. When you are confident with how it works try it with a text file.
Questions (hints)
Are you getting your logic muddled up? Do you even need the line.compare(word)?
http://www.cplusplus.com/reference/s...ring/find.html

Last edited by iamthwee; Oct 10th, 2007 at 2:18 pm.

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Oct 10th, 2007

Re: search in text file

Click to Expand / Collapse Quote originally posted by reaven ...

C++ Syntax (Toggle Plain Text)
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
 
int main()
{
	string line;
	char* word="";
	size_t i;
	fstream dict("c://example.txt",ios::in);
 
	if (!dict.is_open()){ 
		cout << "Unable to open file \n";
		exit(1);
	}
	cout<<"Enter word to search \n";
	cin>>word;
	{
	while(getline(dict,line))   //read line by line
	i = line.find(word);    //try to find the var word in the string line an assign it to i
 
	if (i!=string::npos)      // dont exactly know what it does
  cout<<i<<" not found";      
	else 
		line.compare(word) != 0;  //compare the string line to the var word 
    cout << "result " <<line << endl;
	exit (1);
 
}
 
	return 0;
}
#include "stdafx.h" #include <iostream> #include <fstream> #include <string> using namespace std; int main() { string line; char* word=""; size_t i; fstream dict("c://example.txt",ios::in); if (!dict.is_open()){ cout << "Unable to open file \n"; exit(1); } cout<<"Enter word to search \n"; cin>>word; { while(getline(dict,line)) //read line by line i = line.find(word); //try to find the var word in the string line an assign it to i if (i!=string::npos) // dont exactly know what it does cout<<i<<" not found"; else line.compare(word) != 0; //compare the string line to the var word cout << "result " <<line << endl; exit (1); } return 0; }
I know youre trying to make me understand but am a little lost here really !!
i put comments around the lines to see if i understand what each does correctly , please correct me if am wrong..

thanks a lot

you put the braces in the wrong place. This is how it should look:

C++ Syntax (Toggle Plain Text)
while(getline(dict,line))   //read line by line
{ // start of while
 
    // your code goes here
 
} // end of while
while(getline(dict,line))   //read line by line
{ // start of while

    // your code goes here

} // end of while

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Oct 10th, 2007

Re: search in text file

I put it there but still dont work !!

it is my code right or wrong?

reaven

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