How to Create file but if name exists add incremental number to file name

[thepicos93]

You can check if the file exists using QFile::exists(filename) and if yes, you can add to the new file a new name.

QString new_file(“Qtfile.txt);
if(QFile::exists(new_file) {
 new_file = “Qtfile.txt1.txt);
}

QString new_file(“Qtfile.txt);
if(QFile::exists(new_file) {
 new_file = “Qtfile.txt1.txt);
}

To copy to clipboard, switch view to plain text mode 

And then create the file

[d_stranz]

Here is a somewhat more complete way to do this with any file, which will create a new filename with a number suffix that is one greater than the suffix of the name that was passed in. This code is not tested, so there may be "off-by-one" errors in computing string lengths and positions. It also does not correctly handle the case where a filename has no extension but end in a ".". That is easy to fix but it is a good exercise to find where to do it.

QString	testAndIncrementFilename( const QString & testName )
(
	QFileInfo fInfo( testName );	// Use QFileInfo to test and manipulate filename
	if ( !fInfo.exists() )	// File does not exist, so use it
		return testName;
 
	// Retrieve the extension
	QString ext = fileInfo.suffix();
 
	// and the left-hand side of the path
	QString	path;
	if ( ext.isEmpty() )	// if there is no extension, then the left side is the whole name
	    path = testName;
	else			// otherwise it is everything left of the "."
	    path = testName.left( testName.lastIndexof( '.' ) );
 
	// Now, start at the right end and look for numeric digits
	QString	digits;
	auto pos = path.length() - 1;
	while ( pos > 0 && ( path[ pos ] ).isDigit() )
	{
		// Since we are reading in reverse order, we need to push front instead of back
		digits.push_front( path[ pos ] );
		pos--;
	}
 
	// Save the rest of the path minus the digits for building the new path
	QString	newPath = path.left( pos );
 
	// Build the new number suffix.  Start with 1 as the first increment
	int	number = 1;
	if ( !digits.isEmpty() )
	{
		// Convert the string to an int and increment it
		number = digits.toInt() + 1;
	}
 
	// Convert it back to a string.  Note: if you want something prettier, like "0001", "0002", etc.
	// then use a field width and fill character: QString.arg( number, 4, '0' ).  If you will have more
        // than 10000 files, use a 5-digit field width and consider how badly you are filling up your
        // customer's disk drive
	digits = QString.arg( number );
 
	// Now build the path again
	newPath += digits;	// add the new number
	if ( !ext.isEmpty() )    // if the extensionis not empty add it along with the '.' separator
	{
		newPath += ".";		// add the extension separator
		newPath += ext;		// add the extension
	}
 
	// and here's the new filename
	return newPath;
)

QString	testAndIncrementFilename( const QString & testName )
(
	QFileInfo fInfo( testName );	// Use QFileInfo to test and manipulate filename
	if ( !fInfo.exists() )	// File does not exist, so use it
		return testName;
		
	// Retrieve the extension
	QString ext = fileInfo.suffix();
	
	// and the left-hand side of the path
	QString	path;
	if ( ext.isEmpty() )	// if there is no extension, then the left side is the whole name
	    path = testName;
	else			// otherwise it is everything left of the "."
	    path = testName.left( testName.lastIndexof( '.' ) );
		
	// Now, start at the right end and look for numeric digits
	QString	digits;
	auto pos = path.length() - 1;
	while ( pos > 0 && ( path[ pos ] ).isDigit() )
	{
		// Since we are reading in reverse order, we need to push front instead of back
		digits.push_front( path[ pos ] );
		pos--;
	}
	
	// Save the rest of the path minus the digits for building the new path
	QString	newPath = path.left( pos );
	
	// Build the new number suffix.  Start with 1 as the first increment
	int	number = 1;
	if ( !digits.isEmpty() )
	{
		// Convert the string to an int and increment it
		number = digits.toInt() + 1;
	}
	
	// Convert it back to a string.  Note: if you want something prettier, like "0001", "0002", etc.
	// then use a field width and fill character: QString.arg( number, 4, '0' ).  If you will have more
        // than 10000 files, use a 5-digit field width and consider how badly you are filling up your
        // customer's disk drive
	digits = QString.arg( number );
	
	// Now build the path again
	newPath += digits;	// add the new number
	if ( !ext.isEmpty() )    // if the extensionis not empty add it along with the '.' separator
	{
		newPath += ".";		// add the extension separator
		newPath += ext;		// add the extension
	}
	
	// and here's the new filename
	return newPath;
)

To copy to clipboard, switch view to plain text mode 

I sure hope I didn't just give you the answer to your homework problem...