Qt 4.3: QTemporaryFile Class Reference

|  | Home · All Classes · Main Classes · Grouped Classes · Modules · Functions |

# QTemporaryFile Class Reference
[QtCore module]

The QTemporaryFile class is an I/O device that operates on temporary files. More...

     #include <QTemporaryFile>

Inherits QFile.

Note: All the functions in this class are reentrant.

- List of all members, including inherited members

### Public Functions

- QTemporaryFile ()
- QTemporaryFile ( const QString & templateName )
- QTemporaryFile ( QObject * parent )
- QTemporaryFile ( const QString & templateName, QObject * parent )
- ~QTemporaryFile ()
- bool autoRemove () const
- QString fileName () const
- QString fileTemplate () const
- bool open ()
- void setAutoRemove ( bool b )
- void setFileTemplate ( const QString & name )

- 21 public functions inherited from QFile
- 32 public functions inherited from QIODevice
- 29 public functions inherited from QObject

### Static Public Members

- QTemporaryFile * createLocalFile ( QFile & file )
- QTemporaryFile * createLocalFile ( const QString & fileName )

- 14 static public members inherited from QFile
- 5 static public members inherited from QObject

### Additional Inherited Members

- 1 property inherited from QObject
- 1 public slot inherited from QObject
- 3 signals inherited from QIODevice
- 1 signal inherited from QObject
- 5 protected functions inherited from QIODevice
- 7 protected functions inherited from QObject

## Detailed Description

The QTemporaryFile class is an I/O device that operates on temporary files.

QTemporaryFile is used to create unique temporary files safely. The file itself is created by calling open(). The name of the temporary file is guaranteed to be unique (i.e., you are guaranteed to not overwrite an existing file), and the file will subsequently be removed upon destruction of the QTemporaryFile object. This is an important technique that avoids data corruption for applications that store data in temporary files. The file name is either auto-generated, or created based on a template, which is passed to QTemporaryFile's constructor.

Example:

     {
         QTemporaryFile file;
         if (file.open()) {
             // file.fileName() returns the unique file name
         }

         // the QTemporaryFile destructor removes the temporary file
     }

Reopening a QTemporaryFile after calling close() is safe. For as long as the QTemporaryFile object itself is not destroyed, the unique temporary file will exist and be kept open internally by QTemporaryFile.

A temporary file will have some static part of the name and some part that is calculated to be unique. The default filename qt_temp will be placed into the temporary path as returned by QDir::tempPath().

See also QDir::tempPath() and QFile.

## Member Function Documentation

### QTemporaryFile::QTemporaryFile ()

Constructs a QTemporaryFile in QDir::tempPath(), using the file template "qt_temp.XXXXXX". The file is stored in the system's temporary directory.

See also setFileTemplate() and QDir::tempPath().

### QTemporaryFile::QTemporaryFile ( const QString & templateName )

Constructs a QTemporaryFile with a template filename of templateName. Upon opening the temporary file this will be used to create a unique filename. If the templateName does not contain XXXXXX it will automatically be appended and used as the dynamic portion of the filename.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory.

See also open() and fileTemplate().

### QTemporaryFile::QTemporaryFile ( QObject * parent )

Constructs a QTemporaryFile (with the given parent) in QDir::tempPath(), using the file template "qt_temp.XXXXXX".

See also setFileTemplate().

### QTemporaryFile::QTemporaryFile ( const QString & templateName, QObject * parent )

Constructs a QTemporaryFile with a template filename of templateName and the specified parent. Upon opening the temporary file this will be used to create a unique filename. If the templateName does end in XXXXXX it will automatically be appended and used as the dynamic portion of the filename.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory.

See also open() and fileTemplate().

### QTemporaryFile::~QTemporaryFile ()

Destroys the temporary file object, the file is automatically closed if necessary and if in auto remove mode it will automatically delete the file.

See also autoRemove().

### bool QTemporaryFile::autoRemove () const

Returns true if the QTemporaryFile is in auto remove mode. Auto-remove mode will automatically delete the filename from disk upon destruction. This makes it very easy to create your QTemporaryFile object on the stack, fill it with data, read from it, and finally on function return it will automatically clean up after itself.

Auto-remove is on by default.

See also setAutoRemove() and remove().

### QTemporaryFile * QTemporaryFile::createLocalFile ( QFile & file ) `[static]`

Creates and returns a local temporary file whose contents are a copy of the contents of the given file.

### QTemporaryFile * QTemporaryFile::createLocalFile ( const QString & fileName ) `[static]`

This is an overloaded member function, provided for convenience.

Works on the given fileName rather than an existing QFile object.

### QString QTemporaryFile::fileName () const

Returns the complete unique filename backing the QTemporaryFile object. This string is null before the QTemporaryFile is opened, afterwards it will contain the fileTemplate() plus additional characters to make it unique.

See also fileTemplate().

### QString QTemporaryFile::fileTemplate () const

Returns the set file template. The default file template will be called qt_temp and be placed in QDir::tempPath().

See also setFileTemplate().

### bool QTemporaryFile::open ()

A QTemporaryFile will always be opened in QIODevice::ReadWrite mode, this allows easy access to the data in the file. This function will return true upon success and will set the fileName() to the unique filename used.

See also fileName().

### void QTemporaryFile::setAutoRemove ( bool b )

Sets the QTemporaryFile into auto-remove mode if b is true.

Auto-remove is on by default.

See also autoRemove() and remove().

### void QTemporaryFile::setFileTemplate ( const QString & name )

Sets the static portion of the file name to name. If the file template ends in XXXXXX that will automatically be replaced with the unique part of the filename, otherwise a filename will be determined automatically based on the static portion specified.

If name contains a relative file path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct name if you want use the system's temporary directory.

See also fileTemplate().