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Reading a text file character by character and line by line

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Join Date: Apr 2007

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B.Y

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Reading a text file character by character and line by line

Apr 12th, 2007

I have a s1.txt like this :

3,R,G,T
1,E
9,T,U,Y,O

Now I want to read each character of a each line ...do some analysis and then read each character of the next line ...do some analysis ...so on till EOF.

How do I go abt this?

Well ...I jus wrote a simple program to read a file as below:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;
int main() {
    //char sum = 0;
    char x;
    ifstream inFile("s1.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1);
    }
    while (x != '\n') {
    while (inFile >> x) {    
 
        cout<<"x = "<<x<<endl;
 
    }
    }
    inFile.close();
 
    getchar();
    return 0;
}
#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;
int main() {
    //char sum = 0;
    char x;
    ifstream inFile("s1.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1);
    }
    while (x != '\n') {
    while (inFile >> x) {    
       
        cout<<"x = "<<x<<endl;
        
    }
    }
    inFile.close();
   
    getchar();
    return 0;
}

Doing the above ...I get the entire file as output ... why is'nt it stopping execution as soon as it hits a newline as I mentioned in the first while loop? After I get the first line ...how do I parse through it to analyse each character in the line?

Last edited by WaltP; Apr 12th, 2007 at 3:34 pm. Reason: Added CODE tags -- you actually typed right over what they are when you entered this post...

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Join Date: Aug 2006

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rati

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Re: Reading a text file character by character and line by line

Apr 12th, 2007

You can use strtok function using string.h
It helps u to get the string tokens based on the delimiter u give.

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Join Date: Feb 2007

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thekashyap thekashyap is offline

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Re: Reading a text file character by character and line by line

Apr 12th, 2007

You know there is also www.google.com where you can search for words like "C++ split line"
or "C++ tokens"...
Or use RWCTokenizer..

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Join Date: Dec 2006

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vijayan121 vijayan121 is offline

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Re: Reading a text file character by character and line by line

Apr 12th, 2007

a. read one line
b. strip off unwanted chars (non-printable/whitespace/,)
c. analyze the remaining chars.
repeat a,b,c till end of file.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
struct is_2b_thrown_away
{
  bool operator() ( char ch ) const
  { return !isprint(ch) || isspace(ch) || (ch==',') ; }
};
 
void process_file( const char* file_name )
{
    ifstream file(file_name) ;
    string line ;
    while( getline( file, line ) )
    {
       vector<char> chars ;
       remove_copy_if( line.begin(), line.end(), back_inserter(chars), 
                                      is_2b_thrown_away() ) ;
       // analyse characters in vector chars
    }
}
struct is_2b_thrown_away
{
  bool operator() ( char ch ) const
  { return !isprint(ch) || isspace(ch) || (ch==',') ; }
};

void process_file( const char* file_name )
{
    ifstream file(file_name) ;
    string line ;
    while( getline( file, line ) )
    {
       vector<char> chars ;
       remove_copy_if( line.begin(), line.end(), back_inserter(chars), 
                                      is_2b_thrown_away() ) ;
       // analyse characters in vector chars
    }
}

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Join Date: May 2006

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WaltP

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Re: Reading a text file character by character and line by line

Apr 12th, 2007

Mostly what vijayan121 suggests
a. read one line
b. analyze each character
c. do what you need with each character
repeat a,b,c till end of file.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
string line ;
while( getline( file, line ) )
{
    for (i=0; i < line.length(); i++)
    {
         if (line[i] ...)    // look at each character and process it accordingly
    }
}
string line ;
while( getline( file, line ) )
{
    for (i=0; i < line.length(); i++)
    {
         if (line[i] ...)    // look at each character and process it accordingly
    }
}