reading from file to vector- last line gets repeated

Question

I am trying to read values from a file to a vector

std::vector<float> setTimesArray (std::string flName){
    int i=0, dummy=0;
    float temp;
    std::vector<float> pObs;
    std::string line;
    std::ifstream inFile;
    inFile.open(flName.c_str());
    if(!inFile){
        std::cout<<"\n.obs file not valid. Quitting programme...";
        exit(1);
    }
    while(inFile.good()){
        i++;
        getline(inFile, line);
        if(i>=3){ //I don't want first two lines
            std::istringstream in(line);
            in>>dummy;//discards first value in the line
            in>>temp;
            pObs.push_back(temp);
            in.str(""); //discards remaining part of the line
        }        

    }
    return pObs;
    inFile.close();    
}

Problem is, the last value gets repeated. For example, flName had total 975 lines. Thus pObs must be having size=973 (975-2 initial lines). But the size is 974 and I see that the last value is repeating. What mistake have I made?

That `inFile.close();` is dead code. Put it before the `return`. — Daniel Kamil Kozar, Aug 14 '13 at 21:49
Check that your read was successful before using the result. — chris, Aug 14 '13 at 21:50
when you `getline` the last line of the file, `ifFile.good()` still returns `true`. Therefore you get another iteration of your while loop. — hetepeperfan, Aug 14 '13 at 21:50
This is the wrong *Read while `good`* idiom and for sure a dup. — Benjamin Bannier, Aug 14 '13 at 21:51
@George Daniel ment, that code won't execute, because the function returns/ends before execution of `inFile.close();`. — hetepeperfan, Aug 14 '13 at 21:55
The short answer is that you fail to check the result of your input operation and thus essentially have undefined behaviour. — Kerrek SB, Aug 14 '13 at 22:04

score 4 · Answer 1 · answered Aug 14 '13 at 21:51

4

try:

while (getline(inFile,line))

instead of while(inFile.good()) and remove the getline() call from within the method.

You may also want to change your last two lines of codes to this, as per Daniel Kamil Kozar's suggestion:

inFile.close();
return pObs;

answered Aug 14 '13 at 21:51

Hanlet Escaño

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1

The `inFile.close();` might just as well be removed. – Seth Carnegie Aug 14 '13 at 22:02
1

@Hanlet. Thank you very much. Now it is giving correct results – George Aug 14 '13 at 22:02
@SethCarnegie indeed. I am sure however that this is some type of homework and teachers would look at that to make sure students are doing it. – Hanlet Escaño Aug 14 '13 at 22:04

score 0 · Answer 2 · answered Aug 14 '13 at 21:53

After the last line, good() is still allowed to return true. It doesn't have to return false until after a failed read. Thus, if it returns true, and then fails the read, your line variable won't take a new value. The correct solution would probably be to correct the bounds checking, but in this case, moving the declaration of line into the scope of you while loop and checking for and empty string should correct the issue.

reading from file to vector- last line gets repeated

2 Answers2