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

[Anamika s]

Hi Team,
i am new to Qt.
How to create a file in given path and if file already exists in the given path then we have to add incremental number to file name.
How to achieve this in Qt?

Ex. if i have to save file "QtFile.txt"
but if file already exists in given path then file has to be saved as "QtFile1.txt".



Regards,
Anamika

[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...