Thread: Need help with reading in files.

Well, Ive been struggling trying to get a few of these concepts to work using the getline command and others.


I want to allow a user to enter any search string, including blanks.

**Ive done this**

I want create a final result showing what string was searched for showing each line of text where the search
string occurs.

**Im struggling on how I can display the entire line that the word is found on.**

Also the line number in the file where it occurs and what position in the line the string is located.

** Struggling with doing this , Not sure of how to implement the .find , . size , and .substr **


When the last string is read, I want to report the total
number of occurrences of the string that were found and
how many total lines were in the file.

**Ive done this too**


Here is my code thus far.

Code:

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

using namespace std;

int main()
{



  


ifstream Istream;
ofstream Ostream;


int counter = 0;                                                   
int line = 1;													  
int totalLines = 0;														 
string stringLine;
string userDefinedSearch;



Istream.open("shakespeare.txt");
if (Istream.fail() ) 
{
	cout << "Error opening input file!";
	cin.get();
	return 1;
}



Ostream.open("s_word.txt");
if (Ostream.fail() ) 
{
	cout << "Error creating output file!";
	cin.get();
	return 1;
}



    cout << "Please enter the word you are looking for : " ;
	getline(cin,userDefinedSearch);
	
while (Istream != 0)										 
																
{

    Istream >> stringLine;
	totalLines++;
	
	

	if (stringLine == userDefinedSearch) 
	{
		
		counter++; 
		cout    << userDefinedSearch << endl;
		Ostream << userDefinedSearch << endl;
		
		Ostream << counter << ") occurence is on line: " << line << "  " << userDefinedSearch << endl;
		cout    << counter << ") occurence is on line: " << line << "  " << userDefinedSearch << endl << endl;	
		 
	}


	else 
	{	
	 
	   
	}
	
	


}

 Ostream << counter << " occurences of the word:  " << userDefinedSearch << endl << endl;
 cout    << counter << " occurences of the word : " << userDefinedSearch << endl << endl;
 cout << "There is " << totalLines << " lines in this file." <<  endl;
 Ostream << "There is " << totalLines << " lines in this file." << endl;

Istream.close();
Ostream.close();
return 0;
}

Here is a portion of the output.

Code:

Please enter the word you are looking for : love

.
.
.
.
.
.
.
.
.
.
.
love
1283) occurence is on line: 1  love

love
1284) occurence is on line: 1  love

1284 occurences of the word : love

There is 939197 lines in this file.

I just want the entire line that the word is found on displayed as well as its position in the file. Just kind of confused on how to display the entire actual line the searched word is found in. As well as the format of using the commands to find its position.

Any help would be wonderful. Thanks.

I would use getline() instead of >> operator so that you get the entire line at one time, and can easily detect one line from another. After getting the line with getline() you can use std::string's find method to tokenize it into words (look for spaces).

Getting the exact position in the file where the string starts will prove to be more problematic. One way is to read the entire file into memory so that you can easily calculate the offset of the string from the beginning of the input buffer.

Well trying to replace the getline in my program results in compile errors. Just not sure on how to work it.

I can't see your monitor -- you need to post the code

Code:

std::string line;
getline(cin,line);

Here is an example. replace cin with whatever input stream you are using.

Well how would I implement that, in the code I have placed above?

something like this:

Code:

while (!Istream.eof()) {
    getline(Istream,stringLine);
	totalLines++;
   if (stringLine.find(userDefinedSearch)) > 0) 
   {
	counter++; 
	cout    << userDefinedSearch << endl;
	Ostream << userDefinedSearch << endl;
		
	Ostream << counter << ") occurence is on line: " << line << "  " << userDefinedSearch << endl;
	cout    << counter << ") occurence is on line: " << line << "  " << userDefinedSearch << endl << endl;	
		 
   }
}

All this seems to do is count every single line and imply that whatever is searched for is located on every line. And it reads through the entire document and prints.

However it still is failing to print the actual line that the word is located on.

think about it awhile, it will come to you. I'm not going to write your while program for you. All I posted was a brief description of how to use getline() and check if the line contains the search string. If you want to see the whole line, just use cout to display it on the screen.

Code:

cout << stringLine << endl;

Ok, well thank you.


The only thing that still baffles me is that it is reading in every line in the txt document. Just placing whatever word searched.

Thanks for the help though

what's what that while statement means -- read every line in the text document until end-of-file is reached. You program needs to do that in order to determine line numbers etc. where the search string occurs.

Please don't stop asking questions -- you need to make some effort to solve your program, then post code for more information.

>> while (!Istream.eof())

Ancient Dragon, you should not be using (or advising the use) of eof() in this way. It may cause the loop to be executed one extra time at the end. Use the stream operation as the loop control: while (getline(Istream,stringLine)).

The return value of getline or operator>> evaluates to true if the read is successful, and false if it is not (the stream is returned which is implicitly converted to void* that is null if the stream is in a fail state). Since you want the body of your loop to execute while the read is successful, it is the best solution.

The last call to getline will probably discard the final newline in the data file, but if you use operator>>, any trailing whitespace, including a trailing newline will still be in the file stream after what should be the last time through the loop. If you use eof() at that point, it will return false (since there is one more newline in the file) and the loop will be run again. The read will fail since there is no actual data after the newline, but most code will just process the previous data again. So it's generally better to consistently use the technique that works better in many cases and the same in the rest.

According to this the extraction operator >> and getline() always returns a reference to the ifstream object. That's why I was confused about its use. But a short example test program shows that you're right (as you obviously already know )

Quoted by Ancient D

Getting the exact position in the file where the string starts will prove to be more problematic. One way is to read the entire file into memory so that you can easily calculate the offset of the string from the beginning of the input buffer.

Ouch... . Reading an entire file into memory can not be advised regardless of how small the file is. In fact very few programs warrant the use of such action, with a few exceptions, such as word search programs etc.

I've not read the entire thread but surely the OP could achieve his objectives by reading one line at a time into the buffer? On the other hand you may have already realised this.

Originally Posted by treenef

Ouch... . Reading an entire file into memory can not be advised regardless of how small the file is. In fact very few programs warrant the use of such action, with a few exceptions, such as word search programs etc.

You must be living with 30 year-old hardware. Several meg files is nothing nowdays to read into memory at once. Of course reading really huge files (1 Gig or more) all into memory will be nearly impossible, but there are other techniques used to deal with them which is probably way behond the requirements of this program.