weird behaviour of strstr in qt program

Question

I'm a beginner, made a function which takes input from lineedit converts it into a array and then searches it to find a word. If the word is found it prints successs in a label, otherwise prints error.Problem is that it every time prints error no matter what i enter. What am I doing wrong.

void MainWindow::on_consoleEdit_returnPressed()
{
    QString text = ui->consoleEdit->text();

    char enteredCmd[4096];
    strcpy(enteredCmd, "Some string data");
    text = enteredCmd;
    //enteredCmd contains all the data that text string contains
    char *open = strstr(enteredCmd, "open");

    if(open != NULL) {
        ui->answerLabel->setText("SUCCESS");
    }
    else {
        ui->answerLabel->setText("ERROR");
    }
}

score 1 · Accepted Answer · answered Mar 19 '14 at 15:33

You are testing same string every time, see this:

char enteredCmd[4096];
strcpy(enteredCmd, "Some string data");
text = enteredCmd;

this overrides text value with copy of this "Some string data" string.

Anyway you made this to complicated. QString have lots of functionality useful for you.

void MainWindow::on_consoleEdit_returnPressed()
{
    QString text = ui->consoleEdit->text();

    if(text.contains("open")) {
        ui->answerLabel->setText("SUCCESS");
    } else {
        ui->answerLabel->setText("ERROR");
    }
}

score 0 · Answer 2 · answered Mar 19 '14 at 15:35

Your code is not searching on the text from the line edit. Your code is actually searching for "open" on the string enteredCmd, which always contains "Some string data". Thus, you should always get "ERROR" printed to your answer label.

Here's what I think you are trying to do, using QString instead of strstr:

void MainWindow::on_consoleEdit_returnPressed()
{
    QString text = ui->consoleEdit->text();

    if(text.contains(QStringLiteral("open"))) {
        ui->answerLabel->setText("SUCCESS");
    }
    else {
        ui->answerLabel->setText("ERROR");
    }
}

Why did you used QStringLiteral function? – Amol Borkar Mar 19 '14 at 15:50 — Amol Borkar, Mar 19 '14 at 15:50

score 0 · Answer 3 · answered Mar 19 '14 at 15:36

0

QString is designed to work with many languages so it requires some conversion to get text to a C style eight bit string. You might try something like this:

char *myChar = text.toLatin1().data();

answered Mar 19 '14 at 15:36

Jay

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weird behaviour of strstr in qt program

3 Answers3