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AdRock

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read line of text from file into array

Jan 14th, 2009

I'm trying to get each line of text of a file split into words and then put into an array

I found an exmaple oc cpluscplus.com and their example works but when i try to edit to make changes to read the line of text from a file i get an error on this line:

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char str[] = getline(filename, line);

error message:

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error c2440: 'initializing' : cannot convert from 'std::basic_istream<_Elem,_Traits>' to 'char[]'

I need to be able to read in a line and spilt the words into an array so i can output them

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#include <fstream>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;

int main()
{
	string GetFileName;

	cout << "System >> Enter file to read: \n";

	cout  << "User >> ";
	cin >> GetFileName;
	
	ifstream filename( GetFileName.c_str() );

	if(! filename )
	{
		cout << "Unable to open file: " << GetFileName << endl;

		return EXIT_FAILURE;
	}
	else
	{
		while (getline(filename, line)) //Loop through lines
		{
			char str[] = getline(filename, line);
			char * pch;
			
			pch = strtok (str," ");
			while (pch != NULL)
			{
			printf ("%s\n",pch);
			pch = strtok (NULL, " ");
			}
		}	
		filename.close();
	}
	return EXIT_SUCCESS;
}

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Comatose

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Re: read line of text from file into array

Jan 14th, 2009

Why can't you use a vector? It would be a lot less painful.

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zalezog

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Re: read line of text from file into array

Jan 14th, 2009

Though ,not a good approach but the following approach does work.(if your input contains texts which are separated by more than a couple of newlines,expect some unexpected characters in the output)

Inside the while loop

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while (getline(filename, line)) //Loop through lines
		{
			char str[BUFSIZ] ;//BUFSIZ 
 // already defined in stdio.h 
	
            for(int i=0;line[i];++i)
			str[i]=line[i];
            
            
            char * pch=NULL;
			
			pch = strtok (str," ");
			while (pch!=NULL)
			{
			printf ("%s\n",pch);
			pch = strtok (NULL, " ");
			}
}

Last edited by zalezog : Jan 14th, 2009 at 3:13 pm.

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AdRock

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Re: read line of text from file into array

Jan 14th, 2009

Thanks zalezog

I'm actually getting somewhere.

It does loop through each of the lines but it only outputs the first "token" on each line

This is an example of what i need to get from my file

1.4 0 0.5
2.3 1.7 0.1
0.8 0 0
0.7 1.0 0.2
1.2 1.3 0.5

Is there a way of tweaking the code cos the output is going to be changed later anyway but I need to get the first line into the array pointers [0][0], [0][1],[0][2] etc and the same for the other lines so i can select 2 array pointers and an display the contents

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VernonDozier VernonDozier is offline

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Re: read line of text from file into array

Jan 14th, 2009

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Originally Posted by AdRock

I'm trying to get each line of text of a file split into words and then put into an array

I found an exmaple oc cpluscplus.com and their example works but when i try to edit to make changes to read the line of text from a file i get an error on this line:
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char str[] = getline(filename, line);
char str[] = getline(filename, line);
error message:

I need to be able to read in a line and spilt the words into an array so i can output them
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#include <fstream>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;

int main()
{
	string GetFileName;

	cout << "System >> Enter file to read: \n";

	cout  << "User >> ";
	cin >> GetFileName;
	
	ifstream filename( GetFileName.c_str() );

	if(! filename )
	{
		cout << "Unable to open file: " << GetFileName << endl;

		return EXIT_FAILURE;
	}
	else
	{
		while (getline(filename, line)) //Loop through lines
		{
			char str[] = getline(filename, line);
			char * pch;
			
			pch = strtok (str," ");
			while (pch != NULL)
			{
			printf ("%s\n",pch);
			pch = strtok (NULL, " ");
			}
		}	
		filename.close();
	}
	return EXIT_SUCCESS;
}
#include <fstream> #include <iostream> #include <string> #include <stdio.h> using namespace std; int main() { string GetFileName; cout << "System >> Enter file to read: \n"; cout << "User >> "; cin >> GetFileName; ifstream filename( GetFileName.c_str() ); if(! filename ) { cout << "Unable to open file: " << GetFileName << endl; return EXIT_FAILURE; } else { while (getline(filename, line)) //Loop through lines { char str[] = getline(filename, line); char * pch; pch = strtok (str," "); while (pch != NULL) { printf ("%s\n",pch); pch = strtok (NULL, " "); } } filename.close(); } return EXIT_SUCCESS; }

Is this the whole program? I don't see where line is declared. You have two getline statements when you only need one.

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		while (getline(filename, line)) //Loop through lines
		{
			char str[] = getline(filename, line);

The second one, even if it was syntactically correct, which it is not, overwrites line , which I imagine is supposed to be a string.

You can use char* or string with getline:

http://www.cplusplus.com/reference/i...m/getline.html
http://www.cplusplus.com/reference/string/getline.html

The links above have examples of each.

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zalezog

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Re: read line of text from file into array

Jan 15th, 2009

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Originally Posted by AdRock

Thanks zalezog

I'm actually getting somewhere.

It does loop through each of the lines but it only outputs the first "token" on each line

This is an example of what i need to get from my file

1.4 0 0.5
2.3 1.7 0.1
0.8 0 0
0.7 1.0 0.2
1.2 1.3 0.5

Is there a way of tweaking the code cos the output is going to be changed later anyway but I need to get the first line into the array pointers [0][0], [0][1],[0][2] etc and the same for the other lines so i can select 2 array pointers and an display the contents

If you want the whole line to be printed ,then replace every call with..

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pch=strtok(str,"\n");

I don't understand,when you say

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tweaking the code

If you want to store each word in your file(if that's what you mean)
then something like this might help:

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//fragment code
string get_content[10][BUFSIZ];
    string words_per_line[5];
    //if memory isn't your constraint
	//if there are 10 lines in your file 
	//and if there are more than 5 words in your file
int count_line=0;
	 int count_word=0;

Then update them in your 'while' loop

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while(getline(filename, line))
{
 for(int i=0;line[i];++i)
str[i]=line[i];
            
            
 char * pch=NULL;
char str[BUFSIZ]={0} ;


pch = strtok (str," ");
count_word=0;//reset after each line
while (pch!=NULL)
{
			
		get_content[count_line][count_word]=pch;
            pch = strtok (NULL, " ");
			
		array_words[count_line]=++count_word;
}
		++count_line;
        }

and display them using loops whose control variables are

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count_word
count_line

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Posts: 34

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AdRock

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Re: read line of text from file into array

Jan 15th, 2009

Many thanks for helping me out....i've only been doing C++ for a month

Have i got the code right? It's complaining about 2 undeclared variables

"str" and "array_words"

Once i can get those words or whatever is in the file into my arrays i should be on a roll

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

using namespace std;

int main()
{
	string GetFileName;
	string line;

	cout << "System >> Enter file to read: \n";

	cout  << "User >> ";
	cin >> GetFileName;
	
	ifstream filename( GetFileName.c_str() );

	if(! filename )
	{
		cout << "Unable to open file: " << GetFileName << endl;

		return EXIT_FAILURE;
	}
	else
	{
		//fragment code
		string get_content[10][BUFSIZ];
		string words_per_line[5];
		//if memory isn't your constraint
		//if there are 10 lines in your file 
		//and if there are more than 5 words in your file
		int count_line=0;
		int count_word=0;
	 
		while(getline(filename, line))
		{
			for(int i=0;line[i];++i)
				str[i]=line[i];
                       
				char * pch=NULL;
				char str[BUFSIZ]={0} ;

				pch = strtok (str," ");
				count_word=0;//reset after each line
				while (pch!=NULL)
				{	
					get_content[count_line][count_word]=pch;
					pch = strtok (NULL, " ");
						
					array_words[count_line]=++count_word;
				}
			++count_line;
        }	
		filename.close();
	}
	return EXIT_SUCCESS;
}

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Murtan

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Re: read line of text from file into array

Jan 15th, 2009

If the compiler is complaining, the code is obviously still not right.

Maybe you should define the missing symbols?

try int array_words[10]; right next to where you declare get_content. (They're both used in the same place.)

The declaration for char str[BUFSIZ] needs to come before the for loop that copies into it:

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for(int i =0; line[i];++i)
    str[i]=line[i];
for(int i =0; line[i];++i)
    str[i]=line[i];

That code sure looks like a strcpy() to me, maybe you should look into it.

PS- When posting c++ code, please use c++ code tags
[code=c++]
// Your code here
[/code]

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zalezog

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Re: read line of text from file into array

Jan 16th, 2009

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That code sure looks like a strcpy() to me, maybe you should look into it.

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string line;
char str[BUFSIZ];

1. Murtan is absolutely right when he says that declaration of

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str[BUFSIZ];
int array_words[10];

should be before the loop where the content of 'str' is copied into 'line',same goes with array_words[10]
2.As the declarations of 'str' and 'line' are not ,C-styled strings,i had to use a for loop.Perhaps, AdRock tried using

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