How can I read a text file line by line in Qt?
I'm looking for the Qt equivalent to:
std::ifstream infile;
std::string line;
while (std::getline(infile, line))
{
...
}
Use this code:
QFile inputFile(fileName);
if (inputFile.open(QIODevice::ReadOnly))
{
QTextStream in(&inputFile);
while (!in.atEnd())
{
QString line = in.readLine();
...
}
inputFile.close();
}
This code might be a little simpler:
QFile inputFile(QString("/path/to/file"));
inputFile.open(QIODevice::ReadOnly);
if (!inputFile.isOpen())
return;
QTextStream stream(&inputFile);
for (QString line = stream.readLine();
!line.isNull();
line = stream.readLine()) {
/* process information */
};
Since Qt 5.5 you can use QTextStream::readLineInto
. It behaves similar to std::getline
and is maybe faster as QTextStream::readLine
, because it reuses the string:
QIODevice* device;
QTextStream in(&device);
QString line;
while (in.readLineInto(&line)) {
// ...
}
Here's the example from my code. So I will read a text from 1st line to 3rd line using readLine() and then store to array variable and print into textfield using for-loop :
QFile file("file.txt");
if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
return;
QTextStream in(&file);
QString line[3] = in.readLine();
for(int i=0; i<3; i++)
{
ui->textEdit->append(line[i]);
}
Or something like this, for read from file:
The included lib:
#include "QFile"
#include "QDir"
The Code:
QFile file;
file.setFileName("text.txt");
QDir::setCurrent("C:/Users/USER_NAME/Documents/QTCreatorWorkspace/untitled1");
QTextStream data(&file);
if(file.open(QIODevice::ReadOnly)){
ui->plainTextEdit->insertPlainText(file.readAll());
file.close();
}
else{
//Error statement
}
And for write to file: The Code:
QFile file;
file.setFileName("text.txt");
QDir::setCurrent("C:/Users/USER_NAME/Documents/QTCreatorWorkspace/untitled1");
QTextStream data(&file);
if(file.open(QIODevice::ReadWrite)){
data << ui->plainTextEdit->toPlainText();
file.close();
}
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