Write to many files at once

t021

Hi. I'd like to write "hello" to 1000 files so that the filenames are generated automatically. So far I have this:

QString Filename = "filename";
QFile **db = new QFile*[100];

for(i=0; i<100; i++)
{
db[i]->setFileName(Filename.append(i.toString() ));
if(!db[i]->open(QIODevice::Append | QIODevice::Text)) {exit(1);}
  QTextStream out_stream(&db[i]);
  out_stream << "hello";
db[i]->close();

However this doesn't work. May I ask someone to help me with this a bit. Thanks!

VRonin

@t021 said in Write to many files at once:

this doesn't work

Think about what you are doing here: QFile **db = new QFile*[100]; here lies the problem.

BTW:

for(i=0; i<100; ++i){
QFile tempFile(QStringLiteral("filename%1").arg(i));
if(!tempFile.open(QIODevice::WriteOnly| QIODevice::Text)) continue;
QTextStream out_stream(&tempFile);
out_stream << "hello";
}

jsulm

@t021 No need to have 1000 QFile instances - this is just memory wasting! Just use one like @VRonin does.

t021

@VRonin said in Write to many files at once:

for(i=0; i<100; ++i){
QFile tempFile(QStringLiteral("filename%1").arg(i));
if(!tempFile.open(QIODevice::WriteOnly| QIODevice::Text)) continue;
QTextStream out_stream(&tempFile);
out_stream << "hello";
}

Thank you very much. I cannot use QStringLiteral because I'm using Qt4.

My actual problem is more complicated. I don't just have to write "hello" to each file and forget about them. I need to periodically visit these 1000 files and write more to them. In the next step I may need to write "good bye" to files 217 and 389 only. This is why I need an array of pointers to handle my files. Thanks again!

VRonin

QFile* db[100];
for(int i=0;i<100;++i){
db[i]=new QFile(QString::fromLatin1("filename%1").arg(i));
if(!db[i]->open(QIODevice::WriteOnly| QIODevice::Text)) Q_ASSERT(false);
}
for(i=0; i<100; ++i){
QTextStream out_stream(db[i]);
out_stream << "hello";
}

t021

@VRonin said in Write to many files at once:

QFile* db[100];
for(int i=0;i<100;++i){
db[i]=new QFile(QString::fromLatin1("filename%1").arg(i));
if(!db[i]->open(QIODevice::WriteOnly| QIODevice::Text)) Q_ASSERT(false);
}
for(i=0; i<100; ++i){
QTextStream out_stream(db[i]);
out_stream << "hello";
}

Thank you very much VRONIN! This is exactly what I need, it solved my problem!

VRonin

If the files should not persist once the program is over you might want to consider QTemporaryFile instead of QFile