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how can I use getline() to get multiple fields ?

Posted on 2004-10-20
9
Medium Priority
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Last Modified: 2010-04-01
Hi experts,

I want to get all the fileds with the followings conditions:

1. If column 10 has AA then ignore
2. If column 30 has BB or CC then ignore
3. otherwise, write the file to a new file ( it means write the fileds to a new file without AA, BB, and CCfields )

So my code is like the followings:

String GetField ( )
{
...
}

main()
{
ifstream fin;
ofstream fout;
fin.open("testin.csv");
fout.open("testout.csv");

string line;

while ( getline(fin, line1) && getline(fin, line2) )
{
    string fn1 = GetField ( line, 10, ',' );
    string fn2 = GetField ( line, 30, ',' );
    if ( ( fn1 != "AA" )|| ( fn2 !="BB" ) || ( fn2 !="CC" ) )
     fout << line << endl;
}
}

I know something wrong with my code, but just dont know how to fix it. Anyone can help ? Thanks
0
Comment
Question by:justinY
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9 Comments
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 12363823
You are using getline to read from 'fin' to 'line1' and 'line2' variables (which I don't see declaration from)
Then you are applying GetField to 'line' which is not assigned to any value in your sample code

Maybe you need something similar to:
while ( getline(fin, line) )
{
    string fn1 = GetField ( line, 10, ',' );
    string fn2 = GetField ( line, 30, ',' );
    if ( ( fn1 != "AA" )|| ( fn2 !="BB" ) || ( fn2 !="CC" ) )
     fout << line << endl;
}


0
 

Author Comment

by:justinY
ID: 12364108
Hi,
its not working. I dont know why.
But if I do this  ---   if ( fn1 != "AA"  ) ---- then AA field got deleted  --- I dont understand why cannot delete AA,BB, CC
0
 
LVL 1

Expert Comment

by:gugario
ID: 12365184
Justin,

try to put some partial outputs in the middle of your code...
#include <iostream> on the top,
and then you can do cout << fn1 << endl; cout << fn2 << endl; cout << line << endl;... try to make sure you're reading in the right parameters each step of the way, that might help you debug.

Gustavo.
0
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LVL 15

Expert Comment

by:efn
ID: 12365896
Your condition doesn't do what you said it is supposed to.

Say there is "XX" at column 10.  Then fn1 != "AA", so the whole if condition is true, so the line gets copied out regardless of what is in fn2.

According to your specification, the program should write a line out only if all three conditions are true, not just any one of them.  So you want ands rather than ors.

--efn
0
 
LVL 12

Accepted Solution

by:
OnegaZhang earned 500 total points
ID: 12366776
while ( getline(fin, line) )
{
    string fn1 = GetField ( line, 10, ',' );
    string fn2 = GetField ( line, 30, ',' );
    if ( ( fn1 != "AA" )&& ( fn2 !="BB" ) && ( fn2 !="CC" ) )
     fout << line << endl;
}
0
 

Author Comment

by:justinY
ID: 12370161
Thanks guys,
One last question, I want to load my file into buffer and then getline, how can I do that ?
 
0
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 12370524
you can use a stringstream object.

Dump all your file content to a stringstreem object and then use getline to retrieve line by line. You will need <sstream> header.

Have not tried but I guess is something like this:

// Will need this header
#include <sstream>  

stringstream str;
fin >> str;   // dump all your file into str

while ( getline(str, line) )   // Now extract lines from str
{
    string fn1 = GetField ( line, 10, ',' );
    string fn2 = GetField ( line, 30, ',' );
    if ( ( fn1 != "AA" )&& ( fn2 !="BB" ) && ( fn2 !="CC" ) )
     fout << line << endl;
}
0
 

Author Comment

by:justinY
ID: 12372416
Hey,
I have a compiling error here --- fin >> str
0

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