QFileDevice

PyQt5.QtCore.QFileDevice

Inherits from QIODevice.

Inherited by QFile, QSaveFile.

Description

The QFileDevice class provides an interface for reading from and writing to open files.

QFileDevice is the base class for I/O devices that can read and write text and binary files and resources. QFile offers the main functionality, QFileDevice serves as a base class for sharing functionality with other file devices such as QTemporaryFile, by providing all the operations that can be done on files that have been opened by QFile or QTemporaryFile.

See also

QFile, QTemporaryFile.

Classes

FileHandleFlags

Permissions

Enums

FileError

This enum describes the errors that may be returned by the error() function.

Member	Value	Description
AbortError	6	The operation was aborted.
CopyError	14	The file could not be copied.
FatalError	3	A fatal error occurred.
NoError	0	No error occurred.
OpenError	5	The file could not be opened.
PermissionsError	13	The file could not be accessed.
PositionError	11	The position in the file could not be changed.
ReadError	1	An error occurred when reading from the file.
RemoveError	9	The file could not be removed.
RenameError	10	The file could not be renamed.
ResizeError	12	The file could not be resized.
ResourceError	4	Out of resources (e.g., too many open files, out of memory, etc.)
TimeOutError	7	A timeout occurred.
UnspecifiedError	8	An unspecified error occurred.
WriteError	2	An error occurred when writing to the file.

---

FileHandleFlag

This enum is used when opening a file to specify additional options which only apply to files and not to a generic QIODevice.

Member	Value	Description
AutoCloseHandle	0x0001	The file handle passed into open() should be closed by close(), the default behavior is that close just flushes the file and the application is responsible for closing the file handle. When opening a file by name, this flag is ignored as Qt always owns the file handle and must close it.
DontCloseHandle	0	If not explicitly closed, the underlying file handle is left open when the QFile object is destroyed.

---

FileTime

This enum is used by the fileTime() and setFileTime() functions.

See also

setFileTime(), fileTime().

Member	Value	Description
FileAccessTime	0	When the file was most recently accessed (e.g. read or written to).
FileBirthTime	1	When the file was created (may not be not supported on UNIX).
FileMetadataChangeTime	2	When the file’s metadata was last changed.
FileModificationTime	3	When the file was most recently modified.

---

MemoryMapFlags

This enum describes special options that may be used by the map() function.

Member	Value	Description
MapPrivateOption	0x0001	The mapped memory will be private, so any modifications will not be visible to other processes and will not be written to disk. Any such modifications will be lost when the memory is unmapped. It is unspecified whether modifications made to the file made after the mapping is created will be visible through the mapped memory. This enum value was introduced in Qt 5.4.
NoOptions	0	No options.

---

Permission

This enum is used by the permission() function to report the permissions and ownership of a file. The values may be OR-ed together to test multiple permissions and ownership values.

Warning: Because of differences in the platforms supported by Qt, the semantics of , and are platform-dependent: On Unix, the rights of the owner of the file are returned and on Windows the rights of the current user are returned. This behavior might change in a future Qt version.

Note: On NTFS file systems, ownership and permissions checking is disabled by default for performance reasons. To enable it, include the following line:

# extern Q_CORE_EXPORT int qt_ntfs_permission_lookup;

Permission checking is then turned on and off by incrementing and decrementing qt_ntfs_permission_lookup by 1.

# qt_ntfs_permission_lookup++; // turn checking on
# qt_ntfs_permission_lookup--; // turn it off again

Member	Value	Description
ExeGroup	0x0010	The file is executable by the group.
ExeOther	0x0001	The file is executable by anyone.
ExeOwner	0x1000	The file is executable by the owner of the file.
ExeUser	0x0100	The file is executable by the user.
ReadGroup	0x0040	The file is readable by the group.
ReadOther	0x0004	The file is readable by anyone.
ReadOwner	0x4000	The file is readable by the owner of the file.
ReadUser	0x0400	The file is readable by the user.
WriteGroup	0x0020	The file is writable by the group.
WriteOther	0x0002	The file is writable by anyone.
WriteOwner	0x2000	The file is writable by the owner of the file.
WriteUser	0x0200	The file is writable by the user.

Methods

atEnd() → bool

TODO

---

close()

TODO

---

error() → FileError

Returns the file error status.

The I/O device status returns an error code. For example, if open() returns false, or a read/write operation returns -1, this function can be called to find out the reason why the operation failed.

See also

unsetError().

---

fileName() → str

Returns the name of the file. The default implementation in QFileDevice returns a null string.

---

fileTime(FileTime) → QDateTime

Returns the file time specified by time. If the time cannot be determined return QDateTime() (an invalid date time).

See also

setFileTime(), FileTime, isValid().

---

flush() → bool

Flushes any buffered data to the file. Returns true if successful; otherwise returns false.

---

handle() → int

Returns the file handle of the file.

This is a small positive integer, suitable for use with C library functions such as fdopen() and fcntl(). On systems that use file descriptors for sockets (i.e. Unix systems, but not Windows) the handle can be used with QSocketNotifier as well.

If the file is not open, or there is an error, returns -1.

See also

QSocketNotifier.

---

isSequential() → bool

TODO

---

map(int, int, flags: MemoryMapFlags = NoOptions) → sip.voidptr

Maps size bytes of the file into memory starting at offset. A file should be open for a map to succeed but the file does not need to stay open after the memory has been mapped. When the QFile is destroyed or a new file is opened with this object, any maps that have not been unmapped will automatically be unmapped.

The mapping will have the same open mode as the file (read and/or write), except when using MapPrivateOption, in which case it is always possible to write to the mapped memory.

Any mapping options can be passed through flags.

Returns a pointer to the memory or 0 if there is an error.

See also

unmap().

---

permissions() → Permissions

Returns the complete OR-ed together combination of QFile::Permission for the file.

See also

setPermissions().

---

pos() → int

TODO

---

readData(int) → bytes

TODO

---

readLineData(int) → bytes

TODO

---

resize(int) → bool

Sets the file size (in bytes) sz. Returns true if the resize succeeds; false otherwise. If sz is larger than the file currently is, the new bytes will be set to 0; if sz is smaller, the file is simply truncated.

Warning: This function can fail if the file doesn’t exist.

See also

size().

---

seek(int) → bool

TODO

---

setFileTime(Union[QDateTime, datetime.datetime], FileTime) → bool

Sets the file time specified by fileTime to newDate, returning true if successful; otherwise returns false.

Note: The file must be open to use this function.

See also

fileTime(), FileTime.

---

setPermissions(Union[Permissions, Permission]) → bool

Sets the permissions for the file to the permissions specified. Returns true if successful, or false if the permissions cannot be modified.

Warning: This function does not manipulate ACLs, which may limit its effectiveness.

See also

permissions().

---

size() → int

TODO

---

unmap(sip.voidptr) → bool

Unmaps the memory address.

Returns true if the unmap succeeds; false otherwise.

See also

map().

---

unsetError()

Sets the file’s error to NoError.

See also

error().

---

writeData(bytes) → int

TODO