Having some issue with seekg(binary) and getline (txt/csv)

Question

1.00/5 (1 vote)

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Hi all,

I have written a C++ program I have multiple of CSV file used as input, which I open one at a time and close it after extracting data to a output file which is the only file.

I run getline(inFile,line);
outFile << line << endl;

I run this code, and only part of it is goes to the output file I got, also have spacing randomly to specific file and inconsistent

But when I slower the code, like system("Pause") in the loop, I can get extract what I want perfectly....

Is my program running to fast, why getline would be skipping part of what things I want?

I really have no idea where the problem is coming from, or where to start

Many Thanks!

OP's code:

C++

if (dataname[i] == dataname)
{
    inFile.seekg(datalength[i], ios::beg);
    for (int j = 0; j < datacount[i]; j++)
    {
        getline(inFile, line);
        outFile << line << endl;
    }

}

Posted 4-Jun-13 18:05pm

Member 10093180

Updated 6-Jun-13 0:37am

v3

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Comments

shahrilhafiz 5-Jun-13 1:52am

Did you "Pause" each of the getline? and get the correct data while fully running it cause the data not correct?

Member 10093180 6-Jun-13 5:27am

Yes this is correct

Richard MacCutchan 5-Jun-13 4:19am

Show your code, there must be an error somewhere, and using "Pause" to get round it is not a solution.

Member 10093180 6-Jun-13 5:28am

if (dataname[i] == dataname)
{
inFile.seekg(datalength[i], ios::beg);
for (int j = 0; j < datacount[i]; j++)
{
getline(inFile, line);
outFile << line << endl;
}

}

Many Thanks Richard!!

Richard MacCutchan 6-Jun-13 5:47am

if (dataname[i] == dataname)
What do you expect the result of that statement to be?

Member 10093180 6-Jun-13 5:51am

Employee[1] == Employee

Then use seekg and go to 233434 pre calculated line.length(); in another file, so next time I can access it faster

Richard MacCutchan 6-Jun-13 5:56am

Sorry, but what you are posting is meaningless. Please edit your question and provide a better explanation of how you are reading and writing these files.

Member 10093180 6-Jun-13 6:10am

Honestly, the code is very simple, what I shown is almost there....

I have 200 CSV file, I want employee name AA, in the output file. But I have sudden whitespace or '\n', in the output file which I don't really know what is going on..

Richard MacCutchan 6-Jun-13 6:30am

Yet another meaningless statement, please respond to my other suggestion below.

Stefan_Lang 6-Jun-13 6:44am

You're comparing an apple to a box of apples. That's what Richard means by 'meaningless statement'. The comparison just doesn't make sense. Nor does your explanation.

3 solutions

Solution 2

C++

open the output file
while (there are more input files)
{
    open the next input file
    while (there is more data in the input file)
    {
        read the next line from the input file
        write the line to the output file
    }
    close the input file
}
close the output file

No need for seeks or tests for names etc.

Posted 5-Jun-13 23:51pm

Richard MacCutchan

Comments

Member 10093180 6-Jun-13 6:03am

Thx, This process will be quite if I have 5,000,000 lines...

Richard MacCutchan 6-Jun-13 6:05am

Just another reason to make us suspect that there is a lot more to this issue than you put in your original question.

Member 10093180 6-Jun-13 6:06am

What do you mean?

Richard MacCutchan 6-Jun-13 6:28am

I mean that you have not given all the information rleevant to your problem. Your original post states that you are trying to combine multiple input files (one at a time) into a single output file, using getline etc. Now you are adding more information that suggests there is other processing, and decision taking that affects how you process the data, but you have still not made it clear. Please edit your original question and show clearly (with code) how you are processing your data and where the problem lies.

Member 10093180 6-Jun-13 6:36am

ok thanks mate, I will edit my post again

Richard MacCutchan 6-Jun-13 6:51am

Well, you have edited your post, but you have not given us any useful information.

Member 10093180 6-Jun-13 7:20am

even I post all my code, you won't solve it thanks anyway, please kindly see solution below

Richard MacCutchan 6-Jun-13 7:30am

That's not waht I asked for, I just asked for a proper explanation of the problem.

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Member 10093180 · Accepted Answer · 2013-06-06T01:18:00

Solution 3

seekg() is generally used on streams opened in binary mode. getline() is generally used on streams opened in non-binary (aka text) mode.

Either way, using them together can give results like you describe. The solution: don't use them both on the same stream.

Posted 6-Jun-13 1:18am

Member 10093180

Comments

Richard MacCutchan 6-Jun-13 7:32am

This is not true. I suspect that having removed the seekg calls from your program, you also removed the code containing the bug(s).

AlphaDeltaTheta · Accepted Answer · 2013-06-04T21:53:00

Solution 1

Flush the outfile periodically. Sometimes data doesn't get written properly to the underlying medium.

Call the function after every write operation

C++

outFile.flush();

Good Luck!

Posted 4-Jun-13 21:53pm

AlphaDeltaTheta