Qfile open error - Исправление ошибок и поиск оптимальных решений проблем

QFile Class Reference
^{^{[QtCore module]}}

The QFile class provides an interface for reading from and
writing to files. More…

Inherits QIODevice.

Inherited by QTemporaryFile.

Types

enum FileError { NoError, ReadError, WriteError, FatalError, …, CopyError }
enum Permission { ReadOwner, WriteOwner, ExeOwner, ReadUser, …, ExeOther }

Methods

__init__ (self, QString name, QObject parent)
bool copy (self, QString newName)
FileError error (self)
bool link (self, QString newName)
sip.voidptr map (self, int offset, int size, MemoryMapFlags flags = QFile.NoOptions)
bool open (self, QIODevice.OpenMode flags)
bool open (self, int fd, QIODevice.OpenMode flags)
bool open (self, int fd, QIODevice.OpenMode flags, FileHandleFlags handleFlags)
int pos (self)
bool rename (self, QString newName)
bool resize (self, int sz)
bool seek (self, int offset)
bool unmap (self, sip.voidptr address)

Static Methods

bool copy (QString fileName, QString newName)
QString decodeName (QByteArray localFileName)
bool exists (QString fileName)
bool link (QString oldname, QString newName)
QString readLink (QString fileName)
bool remove (QString fileName)
bool rename (QString oldName, QString newName)
bool resize (QString filename, int sz)
bool setPermissions (QString filename, Permissions permissionSpec)

Detailed Description

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

QFile is an I/O device for reading and writing text and binary
files and resources. A QFile may be
used by itself or, more conveniently, with a QTextStream or QDataStream.

The file name is usually passed in the constructor, but it can
be set at any time using setFileName(). QFile expects the file
separator to be ‘/’ regardless of operating system. The use of
other separators (e.g., ») is not supported.

You can check for a file’s existence using exists(), and remove a file using remove(). (More advanced file system
related operations are provided by QFileInfo and QDir.)

The file is opened with open(),
closed with close(), and flushed
with flush(). Data is usually read
and written using QDataStream or
QTextStream, but you can also call
the QIODevice-inherited functions
read(), readLine(), readAll(), write(). QFile also inherits getChar(), putChar(), and ungetChar(), which work one
character at a time.

The size of the file is returned by size(). You can get the current file position
using pos(), or move to a new file
position using seek(). If you’ve
reached the end of the file, atEnd()
returns true.

Reading Files Directly

The following example reads a text file line by line:

     QFile file("in.txt");
     if (!file.open(QIODevice.ReadOnly | QIODevice.Text))
         return;

     while (!file.atEnd()) {
         QByteArray line = file.readLine();
         process_line(line);
     }

The QIODevice.Text flag passed
to open() tells Qt to convert
Windows-style line terminators («rn») into C++-style terminators
(«n»). By default, QFile assumes binary, i.e. it doesn’t perform
any conversion on the bytes stored in the file.

Using Streams to Read Files

The next example uses QTextStream
to read a text file line by line:

     QFile file("in.txt");
     if (!file.open(QIODevice.ReadOnly | QIODevice.Text))
         return;

     QTextStream in(&file);
     while (!in.atEnd()) {
         QString line = in.readLine();
         process_line(line);
     }

QTextStream takes care of
converting the 8-bit data stored on disk into a 16-bit Unicode
QString. By default, it assumes that the
user system’s local 8-bit encoding is used (e.g., ISO 8859-1 for
most of Europe; see QTextCodec.codecForLocale()
for details). This can be changed using setCodec().

To write text, we can use operator<<(), which is
overloaded to take a QTextStream on
the left and various data types (including QString) on the right:

     QFile file("out.txt");
     if (!file.open(QIODevice.WriteOnly | QIODevice.Text))
         return;

     QTextStream out(&file);
     out << "The magic number is: " << 49 << "n";

QDataStream is similar, in that
you can use operator<<() to write data and operator>>()
to read it back. See the class documentation for details.

When you use QFile, QFileInfo, and
QDir to access the file system with Qt, you
can use Unicode file names. On Unix, these file names are converted
to an 8-bit encoding. If you want to use standard C++ APIs
(<cstdio> or <iostream>) or
platform-specific APIs to access files instead of QFile, you can
use the encodeName() and
decodeName() functions to
convert between Unicode file names and 8-bit file names.

On Unix, there are some special system files (e.g. in
/proc) for which size() will
always return 0, yet you may still be able to read more data from
such a file; the data is generated in direct response to you
calling read(). In this case,
however, you cannot use atEnd() to
determine if there is more data to read (since atEnd() will return true for a file that
claims to have size 0). Instead, you should either call readAll(), or call read() or readLine() repeatedly until no more
data can be read. The next example uses QTextStream to read /proc/modules
line by line:

     QFile file("/proc/modules");
     if (!file.open(QIODevice.ReadOnly | QIODevice.Text))
         return;

     QTextStream in(&file);
     QString line = in.readLine();
     while (!line.isNull()) {
         process_line(line);
         line = in.readLine();
     }

Signals

Unlike other QIODevice
implementations, such as QTcpSocket,
QFile does not emit the aboutToClose(), bytesWritten(), or readyRead() signals. This
implementation detail means that QFile is not suitable for reading
and writing certain types of files, such as device files on Unix
platforms.

Platform Specific Issues

File permissions are handled differently on Linux/Mac OS X and
Windows. In a non writable
directory on Linux, files cannot be created. This is not always the
case on Windows, where, for instance, the ‘My Documents’ directory
usually is not writable, but it is still possible to create files
in it.

Type Documentation

QFile.FileError

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

Constant	Value	Description
QFile.NoError	0	No error occurred.
QFile.ReadError	1	An error occurred when reading from the file.
QFile.WriteError	2	An error occurred when writing to the file.
QFile.FatalError	3	A fatal error occurred.
QFile.ResourceError	4
QFile.OpenError	5	The file could not be opened.
QFile.AbortError	6	The operation was aborted.
QFile.TimeOutError	7	A timeout occurred.
QFile.UnspecifiedError	8	An unspecified error occurred.
QFile.RemoveError	9	The file could not be removed.
QFile.RenameError	10	The file could not be renamed.
QFile.PositionError	11	The position in the file could not be changed.
QFile.ResizeError	12	The file could not be resized.
QFile.PermissionsError	13	The file could not be accessed.
QFile.CopyError	14	The file could not be copied.

QFile.FileHandleFlag

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

Constant	Value	Description
QFile.AutoCloseHandle	0x0001	The file handle passed into open() should be closed by close(), the default behaviour 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.
QFile.DontCloseHandle	0	The file handle passed into open() will not be closed by Qt. The application must ensure that close() is called.

This enum was introduced or modified in Qt 4.8.

The FileHandleFlags type is a typedef for QFlags<FileHandleFlag>. It stores an OR
combination of FileHandleFlag values.

QFile.MemoryMapFlags

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

Constant	Value	Description
QFile.NoOptions	0	No options.

This enum was introduced or modified in Qt 4.4.

QFile.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.

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

Warning: Because of differences in the platforms
supported by Qt, the semantics of ReadUser, WriteUser and ExeUser
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 that Qt does not by default check for permissions on NTFS
file systems, as this may decrease the performance of file handling
considerably. It is possible to force permission checking on NTFS
by including the following code in your source:

 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++; 
 qt_ntfs_permission_lookup--;

The Permissions type is a typedef for QFlags<Permission>. It stores an OR
combination of Permission values.

Method Documentation

QFile.init (self)

Constructs a new file object to represent the file with the
given name.

QFile.init (self, QString name)

QFile.init (self, QObject parent)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a new file object with the given parent.

QFile.init (self, QString name, QObject parent)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a new file object with the given parent to
represent the file with the specified name.

bool QFile.atEnd (self)

Reimplemented from QIODevice.atEnd().

Returns true if the end of the file has been reached; otherwise
returns false.

For regular empty files on Unix (e.g. those in /proc),
this function returns true, since the file system reports that the
size of such a file is 0. Therefore, you should not depend on
atEnd() when reading data from such a file, but rather call
read() until no more data can be
read.

QFile.close (self)

Reimplemented from QIODevice.close().

Calls QFile.flush() and closes
the file. Errors from flush are ignored.

See also QIODevice.close().

bool QFile.copy (self, QString newName)

Copies the file currently specified by fileName() to a file called
newName. Returns true if successful; otherwise returns
false.

Note that if a file with the name newName already exists,
copy() returns false (i.e. QFile will not
overwrite it).

The source file is closed before it is copied.

See also setFileName().

bool QFile.copy (QString fileName, QString newName)

This is an overloaded function.

Copies the file fileName to newName. Returns true
if successful; otherwise returns false.

If a file with the name newName already exists, copy() returns false (i.e., QFile will not overwrite it).

See also rename().

QString QFile.decodeName (QByteArray localFileName)

This does the reverse of QFile.encodeName() using
localFileName.

See also setDecodingFunction() and
encodeName().

QString QFile.decodeName (str localFileName)

This is an overloaded function.

Returns the Unicode version of the given localFileName.
See encodeName() for
details.

QByteArray QFile.encodeName (QString fileName)

By default, this function converts fileName to the local
8-bit encoding determined by the user’s locale. This is sufficient
for file names that the user chooses. File names hard-coded into
the application should only use 7-bit ASCII filename
characters.

See also decodeName()
and setEncodingFunction().

FileError QFile.error (self)

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().

bool QFile.exists (self)

Returns true if the file specified by fileName exists;
otherwise returns false.

bool QFile.exists (QString fileName)

This is an overloaded function.

Returns true if the file specified by fileName() exists; otherwise returns
false.

See also fileName() and
setFileName().

QAbstractFileEngine QFile.fileEngine (self)

QString QFile.fileName (self)

Returns the name set by setFileName() or to the QFile constructors.

See also setFileName() and QFileInfo.fileName().

bool QFile.flush (self)

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

int QFile.handle (self)

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, handle() returns
-1.

This function is not supported on Windows CE.

On Symbian, this function returns -1 if the file was opened
normally, as Symbian OS native file handles do not fit in an int,
and are incompatible with C library functions that the handle would
be used for. If the file was opened using the overloads that take
an open C library file handle / file descriptor, then this function
returns that same handle.

See also QSocketNotifier.

bool QFile.isSequential (self)

Reimplemented from QIODevice.isSequential().

Returns true if the file can only be manipulated sequentially;
otherwise returns false.

Most files support random-access, but some special files may
not.

See also QIODevice.isSequential().

bool QFile.link (self, QString newName)

Creates a link named linkName that points to the file
currently specified by fileName(). What a link is depends on the
underlying filesystem (be it a shortcut on Windows or a symbolic
link on Unix). Returns true if successful; otherwise returns
false.

This function will not overwrite an already existing entity in
the file system; in this case, link() will return false
and set error() to return RenameError.

Note: To create a valid link on Windows, linkName
must have a .lnk file extension.

Note: Symbian filesystem does not support links.

See also setFileName().

bool QFile.link (QString oldname, QString newName)

This is an overloaded function.

Creates a link named linkName that points to the file
fileName. What a link is depends on the underlying
filesystem (be it a shortcut on Windows or a symbolic link on
Unix). Returns true if successful; otherwise returns false.

See also link().

sip.voidptr QFile.map (self, int offset, int size, MemoryMapFlags flags = QFile.NoOptions)

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.

Any mapping options can be passed through flags.

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

Note: On Windows CE 5.0 the file will be closed before
mapping occurs.

This function was introduced in Qt 4.4.

See also unmap() and
QAbstractFileEngine.supportsExtension().

bool QFile.open (self, QIODevice.OpenMode flags)

Reimplemented from QIODevice.open().

Opens the file using OpenMode mode,
returning true if successful; otherwise false.

The mode must be QIODevice.ReadOnly,
QIODevice.WriteOnly,
or QIODevice.ReadWrite. It may
also have additional flags, such as QIODevice.Text and QIODevice.Unbuffered.

Note: In WriteOnly or ReadWrite mode, if the
relevant file does not already exist, this function will try to
create a new file before opening it.

See also QIODevice.OpenMode and
setFileName().

bool QFile.open (self, int fd, QIODevice.OpenMode flags)

bool QFile.open (self, int fd, QIODevice.OpenMode flags, FileHandleFlags handleFlags)

Permissions QFile.permissions (self)

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

See also setPermissions() and setFileName().

Permissions QFile.permissions (QString filename)

This is an overloaded function.

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

int QFile.pos (self)

Reimplemented from QIODevice.pos().

str QFile.readData (self, int maxlen)

Reimplemented from QIODevice.readData().

str QFile.readLineData (self, int maxlen)

Reimplemented from QIODevice.readLineData().

QString QFile.readLink (self)

QString QFile.readLink (QString fileName)

bool QFile.remove (self)

Removes the file specified by fileName(). Returns true if successful;
otherwise returns false.

The file is closed before it is removed.

See also setFileName().

bool QFile.remove (QString fileName)

This is an overloaded function.

Removes the file specified by the fileName given.

Returns true if successful; otherwise returns false.

See also remove().

bool QFile.rename (self, QString newName)

Renames the file currently specified by fileName() to newName. Returns
true if successful; otherwise returns false.

If a file with the name newName already exists, rename()
returns false (i.e., QFile will not
overwrite it).

The file is closed before it is renamed.

See also setFileName().

bool QFile.rename (QString oldName, QString newName)

This is an overloaded function.

Renames the file oldName to newName. Returns true
if successful; otherwise returns false.

If a file with the name newName already exists, rename() returns false (i.e., QFile will not overwrite it).

See also rename().

bool QFile.resize (self, int sz)

Sets the file size (in bytes) sz. Returns true if the
file 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.

See also size() and
setFileName().

bool QFile.resize (QString filename, int sz)

This is an overloaded function.

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

See also resize().

bool QFile.seek (self, int offset)

Reimplemented from QIODevice.seek().

For random-access devices, this function sets the current
position to pos, returning true on success, or false if an
error occurred. For sequential devices, the default behavior is to
do nothing and return false.

Seeking beyond the end of a file: If the position is beyond the
end of a file, then seek() shall not immediately extend the file.
If a write is performed at this position, then the file shall be
extended. The content of the file between the previous end of file
and the newly written data is UNDEFINED and varies between
platforms and file systems.

QFile.setFileName (self, QString name)

Sets the name of the file. The name can have no path, a
relative path, or an absolute path.

Do not call this function if the file has already been
opened.

If the file name has no path or a relative path, the path used
will be the application’s current directory path at the time of
the open() call.

Example:

 QFile file;
 QDir.setCurrent("/tmp");
 file.setFileName("readme.txt");
 QDir.setCurrent("/home");
 file.open(QIODevice.ReadOnly);

Note that the directory separator «/» works for all operating
systems supported by Qt.

See also fileName(),
QFileInfo, and QDir.

bool QFile.setPermissions (self, Permissions permissionSpec)

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

See also permissions() and setFileName().

bool QFile.setPermissions (QString filename, Permissions permissionSpec)

This is an overloaded function.

Sets the permissions for fileName file to
permissions.

int QFile.size (self)

Reimplemented from QIODevice.size().

Returns the size of the file.

For regular empty files on Unix (e.g. those in /proc),
this function returns 0; the contents of such a file are generated
on demand in response to you calling read().

QString QFile.symLinkTarget (self)

Returns the absolute path of the file or directory referred to
by the symlink (or shortcut on Windows) specified by
fileName, or returns an empty string if the fileName
does not correspond to a symbolic link.

This name may not represent an existing file; it is only a
string. QFile.exists() returns
true if the symlink points to an existing file.

This function was introduced in Qt 4.2.

QString QFile.symLinkTarget (QString fileName)

This is an overloaded function.

Returns the absolute path of the file or directory a symlink (or
shortcut on Windows) points to, or a an empty string if the object
isn’t a symbolic link.

This name may not represent an existing file; it is only a
string. QFile.exists() returns
true if the symlink points to an existing file.

This function was introduced in Qt 4.2.

See also fileName() and
setFileName().

bool QFile.unmap (self, sip.voidptr address)

Unmaps the memory address.

Returns true if the unmap succeeds; false otherwise.

This function was introduced in Qt 4.4.

See also map() and QAbstractFileEngine.supportsExtension().

QFile.unsetError (self)

Sets the file’s error to QFile.NoError.

See also error().

int QFile.writeData (self, str data)

Reimplemented from QIODevice.writeData().

Источник

The QFile class provides an interface for reading from and writing to files.
More…

#include <qfile.h>

Public Types
typedef QString(*	DecoderFn) (const QByteArray &localfileName)
	This is a typedef for a pointer to a function with the following signature: More…

typedef QByteArray(*	EncoderFn) (const QString &fileName)
	This is a typedef for a pointer to a function with the following signature: More…

enum	FileError { NoError = 0, ReadError = 1, WriteError = 2, FatalError = 3, ResourceError = 4, OpenError = 5, AbortError = 6, TimeOutError = 7, UnspecifiedError = 8, RemoveError = 9, RenameError = 10, PositionError = 11, ResizeError = 12, PermissionsError = 13, CopyError = 14 }
	This enum describes the errors that may be returned by the error() function. More…

enum	FileHandleFlag { AutoCloseHandle = 0x0001, DontCloseHandle = 0 }
	This enum is used when opening a file to specify additional options which only apply to files and not to a generic QIODevice. More…

enum	MemoryMapFlags { NoOptions = 0 }
	This enum describes special options that may be used by the map() function. More…

enum	Permission { ReadOwner = 0x4000, WriteOwner = 0x2000, ExeOwner = 0x1000, ReadUser = 0x0400, WriteUser = 0x0200, ExeUser = 0x0100, ReadGroup = 0x0040, WriteGroup = 0x0020, ExeGroup = 0x0010, ReadOther = 0x0004, WriteOther = 0x0002, ExeOther = 0x0001 }
	This enum is used by the permission() function to report the permissions and ownership of a file. More…

Public Types inherited from QIODevice
enum	OpenModeFlag { NotOpen = 0x0000, ReadOnly = 0x0001, WriteOnly = 0x0002, ReadWrite = ReadOnly \| WriteOnly, Append = 0x0004, Truncate = 0x0008, Text = 0x0010, Unbuffered = 0x0020 }
	This enum is used with open() to describe the mode in which a device is opened. More…

Public Functions
bool	atEnd () const
	Returns true if the end of the file has been reached; otherwise returns false. More…

virtual void	close ()
	Calls QFile::flush() and closes the file. More…

bool	copy (const QString &newName)
	Copies the file currently specified by fileName() to a file called newName. More…

FileError	error () const
	Returns the file error status. More…

bool	exists () const
	Returns true if the file specified by fileName() exists; otherwise returns false. More…

virtual QAbstractFileEngine *	fileEngine () const
	Returns the QIOEngine for this QFile object. More…

QString	fileName () const
	Returns the name set by setFileName() or to the QFile constructors. More…

bool	flush ()
	Flushes any buffered data to the file. More…

int	handle () const
	Returns the file handle of the file. More…

bool	isSequential () const
	Returns true if the file can only be manipulated sequentially; otherwise returns false. More…

bool	link (const QString &newName)
	Creates a link named linkName that points to the file currently specified by fileName(). More…

uchar *	map (qint64 offset, qint64 size, MemoryMapFlags flags=NoOptions)
	Maps size bytes of the file into memory starting at offset. More…

bool	open (OpenMode flags)
	Opens the file using OpenMode mode, returning true if successful; otherwise false. More…

bool	open (FILE *f, OpenMode flags)
	Opens the existing file handle fh in the given mode. More…

bool	open (int fd, OpenMode flags)
	Opens the existing file descriptor fd in the given mode. More…

bool	open (FILE *f, OpenMode ioFlags, FileHandleFlags handleFlags)
	Opens the existing file handle fh in the given mode. More…

bool	open (int fd, OpenMode ioFlags, FileHandleFlags handleFlags)
	Opens the existing file descriptor fd in the given mode. More…

Permissions	permissions () const
	Returns the complete OR-ed together combination of QFile::Permission for the file. More…

qint64	pos () const
	Reimplemented Function More…

	QFile ()

	QFile (const QString &name)
	Constructs a new file object to represent the file with the given name. More…

	QFile (QObject *parent)
	Constructs a new file object with the given parent. More…

	QFile (const QString &name, QObject *parent)
	Constructs a new file object with the given parent to represent the file with the specified name. More…

QString	readLink () const
	Use symLinkTarget() instead. More…

bool	remove ()
	Removes the file specified by fileName(). More…

bool	rename (const QString &newName)
	Renames the file currently specified by fileName() to newName. More…

bool	resize (qint64 sz)
	Sets the file size (in bytes) sz. More…

bool	seek (qint64 offset)
	For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred. More…

void	setFileName (const QString &name)
	Sets the name of the file. More…

bool	setPermissions (Permissions permissionSpec)
	Sets the permissions for the file to the permissions specified. More…

qint64	size () const
	Returns the size of the file. More…

QString	symLinkTarget () const
	Returns the absolute path of the file or directory a symlink (or shortcut on Windows) points to, or a an empty string if the object isn’t a symbolic link. More…

bool	unmap (uchar *address)
	Unmaps the memory address. More…

void	unsetError ()
	Sets the file’s error to QFile::NoError. More…

	~QFile ()
	Destroys the file object, closing it if necessary. More…

Public Functions inherited from QIODevice
virtual qint64	bytesAvailable () const
	Returns the number of bytes that are available for reading. More…

virtual qint64	bytesToWrite () const
	For buffered devices, this function returns the number of bytes waiting to be written. More…

virtual bool	canReadLine () const
	Returns true if a complete line of data can be read from the device; otherwise returns false. More…

QString	errorString () const
	Returns a human-readable description of the last device error that occurred. More…

bool	getChar (char *c)
	Reads one character from the device and stores it in c. More…

bool	isOpen () const
	Returns true if the device is open; otherwise returns false. More…

bool	isReadable () const
	Returns true if data can be read from the device; otherwise returns false. More…

bool	isTextModeEnabled () const
	Returns true if the Text flag is enabled; otherwise returns false. More…

bool	isWritable () const
	Returns true if data can be written to the device; otherwise returns false. More…

OpenMode	openMode () const
	Returns the mode in which the device has been opened; i.e. More…

qint64	peek (char *data, qint64 maxlen)
	Reads at most maxSize bytes from the device into data, without side effects (i. More…

QByteArray	peek (qint64 maxlen)
	Peeks at most maxSize bytes from the device, returning the data peeked as a QByteArray. More…

bool	putChar (char c)
	Writes the character c to the device. More…

	QIODevice ()
	Constructs a QIODevice object. More…

	QIODevice (QObject *parent)
	Constructs a QIODevice object with the given parent. More…

qint64	read (char *data, qint64 maxlen)
	Reads at most maxSize bytes from the device into data, and returns the number of bytes read. More…

QByteArray	read (qint64 maxlen)
	Reads at most maxSize bytes from the device, and returns the data read as a QByteArray. More…

QByteArray	readAll ()
	Reads all available data from the device, and returns it as a QByteArray. More…

qint64	readLine (char *data, qint64 maxlen)
	This function reads a line of ASCII characters from the device, up to a maximum of maxSize — 1 bytes, stores the characters in data, and returns the number of bytes read. More…

QByteArray	readLine (qint64 maxlen=0)
	Reads a line from the device, but no more than maxSize characters, and returns the result as a QByteArray. More…

virtual bool	reset ()
	Seeks to the start of input for random-access devices. More…

void	setTextModeEnabled (bool enabled)
	If enabled is true, this function sets the Text flag on the device; otherwise the Text flag is removed. More…

void	ungetChar (char c)
	Puts the character c back into the device, and decrements the current position unless the position is 0. More…

virtual bool	waitForBytesWritten (int msecs)
	For buffered devices, this function waits until a payload of buffered written data has been written to the device and the bytesWritten() signal has been emitted, or until msecs milliseconds have passed. More…

virtual bool	waitForReadyRead (int msecs)
	Blocks until new data is available for reading and the readyRead() signal has been emitted, or until msecs milliseconds have passed. More…

qint64	write (const char *data, qint64 len)
	Writes at most maxSize bytes of data from data to the device. More…

qint64	write (const char *data)
	Writes data from a zero-terminated string of 8-bit characters to the device. More…

qint64	write (const QByteArray &data)
	Writes the content of byteArray to the device. More…

virtual	~QIODevice ()
	The destructor is virtual, and QIODevice is an abstract base class. More…

Public Functions inherited from QObject
bool	blockSignals (bool b)
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More…

const QObjectList &	children () const
	Returns a list of child objects. More…

bool	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const

bool	disconnect (const char signal=0, const QObject receiver=0, const char *member=0)

bool	disconnect (const QObject receiver, const char member=0)

void	dumpObjectInfo ()
	Dumps information about signal connections, etc. More…

void	dumpObjectTree ()
	Dumps a tree of children to the debug output. More…

QList< QByteArray >	dynamicPropertyNames () const
	Returns the names of all properties that were dynamically added to the object using setProperty(). More…

virtual bool	event (QEvent *)
	This virtual function receives events to an object and should return true if the event e was recognized and processed. More…

virtual bool	eventFilter (QObject , QEvent )
	Filters events if this object has been installed as an event filter for the watched object. More…

template<typename T >
T	findChild (const QString &aName=QString()) const
	Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More…

template<typename T >
QList< T >	findChildren (const QString &aName=QString()) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. More…

template<typename T >
QList< T >	findChildren (const QRegExp &re) const

bool	inherits (const char *classname) const
	Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false. More…

void	installEventFilter (QObject *)
	Installs an event filter filterObj on this object. More…

bool	isWidgetType () const
	Returns true if the object is a widget; otherwise returns false. More…

void	killTimer (int id)
	Kills the timer with timer identifier, id. More…

virtual const QMetaObject *	metaObject () const
	Returns a pointer to the meta-object of this object. More…

void	moveToThread (QThread *thread)
	Changes the thread affinity for this object and its children. More…

QString	objectName () const

QObject *	parent () const
	Returns a pointer to the parent object. More…

QVariant	property (const char *name) const
	Returns the value of the object’s name property. More…

Q_INVOKABLE	QObject (QObject *parent=0)
	Constructs an object with parent object parent. More…

void	removeEventFilter (QObject *)
	Removes an event filter object obj from this object. More…

void	setObjectName (const QString &name)

void	setParent (QObject *)
	Makes the object a child of parent. More…

bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object’s name property to value. More…

void	setUserData (uint id, QObjectUserData *data)

bool	signalsBlocked () const
	Returns true if signals are blocked; otherwise returns false. More…

int	startTimer (int interval)
	Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More…

QThread *	thread () const
	Returns the thread in which the object lives. More…

QObjectUserData *	userData (uint id) const

virtual	~QObject ()
	Destroys the object, deleting all its child objects. More…

Static Public Functions
static bool	copy (const QString &fileName, const QString &newName)
	Copies the file fileName to newName. More…

static QString	decodeName (const QByteArray &localFileName)
	This does the reverse of QFile::encodeName() using localFileName. More…

static QString	decodeName (const char *localFileName)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Returns the Unicode version of the given localFileName. More…

static QByteArray	encodeName (const QString &fileName)
	By default, this function converts fileName to the local 8-bit encoding determined by the user’s locale. More…

static bool	exists (const QString &fileName)
	Returns true if the file specified by fileName exists; otherwise returns false. More…

static bool	link (const QString &oldname, const QString &newName)
	Creates a link named linkName that points to the file fileName. More…

static Permissions	permissions (const QString &filename)
	Returns the complete OR-ed together combination of QFile::Permission for fileName. More…

static QString	readLink (const QString &fileName)
	Use symLinkTarget() instead. More…

static bool	remove (const QString &fileName)
	Removes the file specified by the fileName given. More…

static bool	rename (const QString &oldName, const QString &newName)
	Renames the file oldName to newName. More…

static bool	resize (const QString &filename, qint64 sz)
	Sets fileName to size (in bytes) sz. More…

static void	setDecodingFunction (DecoderFn)
	Sets the function for decoding 8-bit file names. More…

static void	setEncodingFunction (EncoderFn)
	Sets the function for encoding Unicode file names. More…

static bool	setPermissions (const QString &filename, Permissions permissionSpec)
	Sets the permissions for fileName file to permissions. More…

static QString	symLinkTarget (const QString &fileName)
	Returns the absolute path of the file or directory referred to by the symlink (or shortcut on Windows) specified by fileName, or returns an empty string if the fileName does not correspond to a symbolic link. More…

Static Public Functions inherited from QObject
static bool	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More…

static bool	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	Disconnects signal in object sender from method in object receiver. More…

static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)

static uint	registerUserData ()

static QString	tr (const char sourceText, const char comment=0, int n=-1)

static QString	trUtf8 (const char sourceText, const char comment=0, int n=-1)

Protected Functions
	QFile (QFilePrivate &dd, QObject *parent=0)

qint64	readData (char *data, qint64 maxlen)
	Reimplemented Function More…

qint64	readLineData (char *data, qint64 maxlen)
	Reimplemented Function More…

qint64	writeData (const char *data, qint64 len)
	Reimplemented Function More…

Protected Functions inherited from QIODevice
	QIODevice (QIODevicePrivate &dd, QObject *parent=0)

void	setErrorString (const QString &errorString)
	Sets the human readable description of the last device error that occurred to str. More…

void	setOpenMode (OpenMode openMode)
	Sets the OpenMode of the device to openMode. More…

Protected Functions inherited from QObject
virtual void	childEvent (QChildEvent *)
	This event handler can be reimplemented in a subclass to receive child events. More…

virtual void	connectNotify (const char *signal)
	This virtual function is called when something has been connected to signal in this object. More…

virtual void	customEvent (QEvent *)
	This event handler can be reimplemented in a subclass to receive custom events. More…

virtual void	disconnectNotify (const char *signal)
	This virtual function is called when something has been disconnected from signal in this object. More…

	QObject (QObjectPrivate &dd, QObject *parent=0)

int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal. More…

QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0. More…

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *)
	This event handler can be reimplemented in a subclass to receive timer events for the object. More…

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	Schedules this object for deletion. More…

Signals inherited from QIODevice
void	aboutToClose ()
	This signal is emitted when the device is about to close. More…

void	bytesWritten (qint64 bytes)
	This signal is emitted every time a payload of data has been written to the device. More…

void	readChannelFinished ()
	This signal is emitted when the input (reading) stream is closed in this device. More…

void	readyRead ()
	This signal is emitted once every time new data is available for reading from the device. More…

Signals inherited from QObject
void	destroyed (QObject *=0)
	This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More…

Static Public Variables inherited from QObject
static const QMetaObject	staticMetaObject
	This variable stores the meta-object for the class. More…

Protected Variables inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Static Protected Variables inherited from QObject
static const QMetaObject	staticQtMetaObject

Related Functions inherited from QObject
T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()

QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QRegExp &regExp)()

T *	qobject_cast (QObject *object)

	QObjectList

void *	qt_find_obj_child (QObject parent, const char type, const QString &name)
	Returns a pointer to the object named name that inherits type and with a given parent. More…

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

Note: This class or function is reentrant.

QFile is an I/O device for reading and writing text and binary files and The Qt Resource System{resources}. A QFile may be used by itself or, more conveniently, with a QTextStream or QDataStream.

The file name is usually passed in the constructor, but it can be set at any time using setFileName(). QFile expects the file separator to be ‘/’ regardless of operating system. The use of other separators (e.g., ») is not supported.

You can check for a file’s existence using exists(), and remove a file using remove(). (More advanced file system related operations are provided by QFileInfo and QDir.)

The file is opened with open(), closed with close(), and flushed with flush(). Data is usually read and written using QDataStream or QTextStream, but you can also call the QIODevice-inherited functions read(), readLine(), readAll(), write(). QFile also inherits getChar(), putChar(), and ungetChar(), which work one character at a time.

The size of the file is returned by size(). You can get the current file position using pos(), or move to a new file position using seek(). If you’ve reached the end of the file, atEnd() returns true.

Reading Files Directly

The following example reads a text file line by line:

QFile file(«in.txt»);

return;

while (!file.atEnd()) {

process_line(line);

}

The QIODevice::Text flag passed to open() tells Qt to convert Windows-style line terminators («\r\n») into C++-style terminators («\n»). By default, QFile assumes binary, i.e. it doesn’t perform any conversion on the bytes stored in the file.

Using Streams to Read Files

The next example uses QTextStream to read a text file line by line:

QFile file(«in.txt»);

return;

while (!in.atEnd()) {

QString line = in.readLine();

process_line(line);

}

QTextStream takes care of converting the 8-bit data stored on disk into a 16-bit Unicode QString. By default, it assumes that the user system’s local 8-bit encoding is used (e.g., ISO 8859-1 for most of Europe; see QTextCodec::codecForLocale() for details). This can be changed using setCodec().

To write text, we can use operator<<(), which is overloaded to take a QTextStream on the left and various data types (including QString) on the right:

QFile file(«out.txt»);

return;

out << «The magic number is: « << 49 << «n»;

QDataStream is similar, in that you can use operator<<() to write data and operator>>() to read it back. See the class documentation for details.

When you use QFile, QFileInfo, and QDir to access the file system with Qt, you can use Unicode file names. On Unix, these file names are converted to an 8-bit encoding. If you want to use standard C++ APIs ( <cstdio> or <iostream>) or platform-specific APIs to access files instead of QFile, you can use the encodeName() and decodeName() functions to convert between Unicode file names and 8-bit file names.

On Unix, there are some special system files (e.g. in /proc) for which size() will always return 0, yet you may still be able to read more data from such a file; the data is generated in direct response to you calling read(). In this case, however, you cannot use atEnd() to determine if there is more data to read (since atEnd() will return true for a file that claims to have size 0). Instead, you should either call readAll(), or call read() or readLine() repeatedly until no more data can be read. The next example uses QTextStream to read /proc/modules line by line:

QFile file(«/proc/modules»);

return;

QString line = in.readLine();

process_line(line);

line = in.readLine();

}

Signals

Unlike other QIODevice implementations, such as QTcpSocket, QFile does not emit the aboutToClose(), bytesWritten(), or readyRead() signals. This implementation detail means that QFile is not suitable for reading and writing certain types of files, such as device files on Unix platforms.

Platform Specific Issues

File permissions are handled differently on Linux/Mac OS X and Windows. In a non writable directory on Linux, files cannot be created. This is not always the case on Windows, where, for instance, the ‘My Documents’ directory usually is not writable, but it is still possible to create files in it.

See also: QTextStream, QDataStream, QFileInfo, QDir, {The Qt Resource System}

Definition at line 65 of file qfile.h.

◆ DecoderFn

◆ EncoderFn

◆ FileError

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

NoError No error occurred.
ReadError An error occurred when reading from the file.
WriteError An error occurred when writing to the file.
FatalError A fatal error occurred.
ResourceError
OpenError The file could not be opened.
AbortError The operation was aborted.
TimeOutError A timeout occurred.
UnspecifiedError An unspecified error occurred.
RemoveError The file could not be removed.
RenameError The file could not be renamed.
PositionError The position in the file could not be changed.
ResizeError The file could not be resized.
PermissionsError The file could not be accessed.
CopyError The file could not be copied.

ConnectError

Enumerator
NoError
ReadError
WriteError
FatalError
ResourceError
OpenError
AbortError
TimeOutError
UnspecifiedError
RemoveError
RenameError
PositionError
ResizeError
PermissionsError
CopyError

Definition at line 74 of file qfile.h.

74 {

90 #ifdef QT3_SUPPORT

91 , ConnectError = 30

92 #endif

93 };

◆ FileHandleFlag

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

Since: 4.8

AutoCloseHandle The file handle passed into open() should be closed by close(), the default behaviour 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 The file handle passed into open() will not be closed by Qt. The application must ensure that close() is called.

Enumerator
AutoCloseHandle
DontCloseHandle

Definition at line 103 of file qfile.h.

◆ MemoryMapFlags

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

Since: 4.4

NoOptions No options.

Enumerator
NoOptions

Definition at line 180 of file qfile.h.

◆ 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.

ReadOwner The file is readable by the owner of the file.
WriteOwner The file is writable by the owner of the file.
ExeOwner The file is executable by the owner of the file.
ReadUser The file is readable by the user.
WriteUser The file is writable by the user.
ExeUser The file is executable by the user.
ReadGroup The file is readable by the group.
WriteGroup The file is writable by the group.
ExeGroup The file is executable by the group.
ReadOther The file is readable by anyone.
WriteOther The file is writable by anyone.
ExeOther The file is executable by anyone.

Warning: Because of differences in the platforms supported by Qt, the semantics of ReadUser, WriteUser and ExeUser 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 that Qt does not by default check for permissions on NTFS file systems, as this may decrease the performance of file handling considerably. It is possible to force permission checking on NTFS by including the following code in your source:

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

Enumerator
ReadOwner
WriteOwner
ExeOwner
ReadUser
WriteUser
ExeUser
ReadGroup
WriteGroup
ExeGroup
ReadOther
WriteOther
ExeOther

Definition at line 95 of file qfile.h.

◆ QFile() [1/5]

◆ QFile() [2/5]

QFile::QFile

(

const QString &

name

)

Constructs a new file object to represent the file with the given name.

Definition at line 431 of file qfile.cpp.

433 {

435 d->fileName = name;

436 }

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

QIODevice()

Constructs a QIODevice object.

◆ QFile() [3/5]

QFile::QFile

(

QObject *

parent

)

explicit

Constructs a new file object with the given parent.

Definition at line 424 of file qfile.cpp.

426 {

427 }

QIODevice()

Constructs a QIODevice object.

Constructs a new file object with the given parent to represent the file with the specified name.

Definition at line 441 of file qfile.cpp.

443 {

445 d->fileName = name;

446 }

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

QIODevice()

Constructs a QIODevice object.

◆ ~QFile()

Destroys the file object, closing it if necessary.

Definition at line 459 of file qfile.cpp.

460 {

462 }

virtual void close()

Calls QFile::flush() and closes the file.

◆ QFile() [5/5]

Warning: This function is not part of the public interface.

Definition at line 450 of file qfile.cpp.

452 {

453 }

QIODevice()

Constructs a QIODevice object.

◆ atEnd()

bool QFile::atEnd

(

)

const

virtual

Returns true if the end of the file has been reached; otherwise returns false.

For regular empty files on Unix (e.g. those in /proc), this function returns true, since the file system reports that the size of such a file is 0. Therefore, you should not depend on atEnd() when reading data from such a file, but rather call read() until no more data can be read.

Reimplemented from QIODevice.

Definition at line 1735 of file qfile.cpp.

Referenced by copy(), QBenchmarkValgrindUtils::extractResult(), fontFile(), QHostInfo::localDomainName(), qt_parseEtcLpPrinters(), qt_parseNsswitchConf(), qt_parsePrintcap(), qt_parsePrintersConf(), and QCoreApplicationData::~QCoreApplicationData().

1736 {

1738

1739

1740 if (!d->buffer.isEmpty())

1741 return false;

1742

1744 return true;

1745

1746 if (!d->ensureFlushed())

1747 return false;

1748

1749

1751

1752

1753 return d->fileEngine->atEnd();

1754 }

1755

1756

1757

1758 if (pos() < d->cachedSize)

1759 return false;

1760

1761

1763 }

bool isOpen() const

Returns true if the device is open; otherwise returns false.

qint64 pos() const

Reimplemented Function

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

virtual qint64 bytesAvailable() const

Returns the number of bytes that are available for reading.

◆ close()

void QFile::close

(

)

virtual

Calls QFile::flush() and closes the file.

Errors from flush are ignored.

See also: QIODevice::close()

Reimplemented from QIODevice.

Definition at line 1680 of file qfile.cpp.

Referenced by QNetworkManagerEngine::bytesReceived(), QConnmanEngine::bytesReceived(), QNetworkManagerEngine::bytesWritten(), QConnmanEngine::bytesWritten(), QUnixPrintWidgetPrivate::checkFields(), QNetworkAccessFileBackend::closeDownstreamChannel(), QMacPasteboardMimeVCard::convertFromMime(), copy(), QTemporaryFile::createLocalFile(), QNetworkDiskCache::data(), QGraphicsAnchorLayoutPrivate::dumpGraph(), QPdfEnginePrivate::embedFont(), QtopiaPrintEngine::end(), QZipReader::extractAll(), QNetworkDiskCache::fileMetaData(), fontPath(), QDirectFBPixmapData::fromFile(), QGLPixmapData::fromFile(), QTransportAuthPrivate::getClientKey(), QScriptEngine::importExtension(), QAxScriptManager::load(), QTextBrowser::loadResource(), QTextDocument::loadResource(), QPictureIO::pictureFormat(), qt_parse_pattern(), QPictureIO::read(), registerFont(), remove(), rename(), setFileName(), QSslSocketBackendPrivate::startHandshake(), QNetworkAccessFileBackend::uploadReadyReadSlot(), QPictureIO::write(), QCoreApplicationData::~QCoreApplicationData(), ~QFile(), and QTemporaryFile::~QTemporaryFile().

1681 {

1684 return;

1685 bool flushed = flush();

1687

1688

1689 d->lastWasWrite = false;

1690 d->writeBuffer.clear();

1691

1692

1693 if (d->fileEngine->close() && flushed)

1695 else if (flushed)

1696 d->setError(d->fileEngine->error(), d->fileEngine->errorString());

1697 }

virtual void close()

First emits aboutToClose(), then closes the device and sets its OpenMode to NotOpen.

bool isOpen() const

Returns true if the device is open; otherwise returns false.

bool flush()

Flushes any buffered data to the file.

void unsetError()

Sets the file's error to QFile::NoError.

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

◆ copy() [1/2]

bool QFile::copy

(

const QString &

newName

)

Copies the file currently specified by fileName() to a file called newName.

Returns true if successful; otherwise returns false.

Note that if a file with the name newName already exists, copy() returns false (i.e. QFile will not overwrite it).

The source file is closed before it is copied.

See also: setFileName()

Definition at line 926 of file qfile.cpp.

Referenced by QDragManager::drag(), QDirModel::dropMimeData(), and QFileSystemModel::dropMimeData().

927 {

929 if (d->fileName.isEmpty()) {

930 qWarning(«QFile::copy: Empty or null file name»);

931 return false;

932 }

934

935

936

938 return false;

939 }

945 return true;

946 } else {

947 bool error = false;

949 error = true;

950 d->setError(QFile::CopyError, tr(«Cannot open %1 for input»).arg(d->fileName));

951 } else {

953 #ifdef QT_NO_TEMPORARYFILE

956 error = true;

957 #else

959 if (!out.open()) {

961 if (!out.open())

962 error = true;

963 }

964 #endif

965 if (error) {

966 out.close();

969 } else {

970 char block[4096];

971 qint64 totalRead = 0;

972 while(!atEnd()) {

973 qint64 in = read(block, sizeof(block));

974 if (in <= 0)

975 break;

976 totalRead += in;

977 if(in != out.write(block, in)) {

980 error = true;

981 break;

982 }

983 }

984

985 if (totalRead != size()) {

986

987

988 error = true;

989 }

990 if (!error && !out.rename(newName)) {

991 error = true;

993 d->setError(QFile::CopyError, tr(«Cannot create %1 for output»).arg(newName));

994 }

995 #ifdef QT_NO_TEMPORARYFILE

996 if (error)

997 out.remove();

998 #else

999 if (!error)

1000 out.setAutoRemove(false);

1001 #endif

1002 }

1003 }

1004 if(!error) {

1008 return true;

1009 }

1010 }

1011 }

1012 return false;

1013 }

bool open(OpenMode flags)

Opens the file using OpenMode mode, returning true if successful; otherwise false.

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

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

static QString tr(const char *sourceText, const char *comment=0, int n=-1)

QLatin1String(DBUS_INTERFACE_DBUS))) Q_GLOBAL_STATIC_WITH_ARGS(QString

The QString class provides a Unicode character string.

qint64 read(char *data, qint64 maxlen)

Reads at most maxSize bytes from the device into data, and returns the number of bytes read…

bool exists() const

Returns true if the file specified by fileName() exists; otherwise returns false. …

Q_CORE_EXPORT void qWarning(const char *,…)

qint64 size() const

Returns the size of the file.

static QString tempPath()

Returns the absolute path of the system's temporary directory.

void unsetError()

Sets the file's error to QFile::NoError.

QString arg(qlonglong a, int fieldwidth=0, int base=10, const QChar &fillChar=QLatin1Char(‘ ‘)) const Q_REQUIRED_RESULT

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

bool setPermissions(Permissions permissionSpec)

Sets the permissions for the file to the permissions specified.

bool copy(const QString &newName)

Copies the file currently specified by fileName() to a file called newName.

Permissions permissions() const

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

void setFileTemplate(const QString &name)

Sets the static portion of the file name to name.

FileError error() const

Returns the file error status.

The QFileInfo class provides system-independent file information.

bool atEnd() const

Returns true if the end of the file has been reached; otherwise returns false.

virtual void close()

Calls QFile::flush() and closes the file.

◆ copy() [2/2]

bool QFile::copy	(	const QString &	fileName,
		const QString &	newName
	)

static

Copies the file fileName to newName.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

If a file with the name newName already exists, copy() returns false (i.e., QFile will not overwrite it).

See also: rename()

Definition at line 1031 of file qfile.cpp.

1032 {

1033 return QFile(fileName).copy(newName);

1034 }

◆ decodeName() [1/2]

This does the reverse of QFile::encodeName() using localFileName.

See also: setDecodingFunction(), encodeName()

Definition at line 552 of file qfile.cpp.

Referenced by QCoreApplication::applicationFilePath(), QFontEngineQPF::cleanUpAfterClientCrash(), QWSServerPrivate::cleanupFonts(), QZipReader::extractAll(), QFileSystemEngine::getLinkTarget(), QFileSystemEngine::homePath(), QGuiPlatformPlugin::iconThemeSearchPaths(), initDefaultPaths(), loadSingleEngine(), QHostInfo::localDomainName(), QFontEngineQPF::QFontEngineQPF(), QFileSystemEntry::resolveFilePath(), QFileSystemEngine::resolveGroupName(), QFileSystemEngine::resolveUserName(), and QFileSystemEngine::tempPath().

553 {

555 }

static QFile::DecoderFn decoder

◆ decodeName() [2/2]

QString QFile::decodeName

(

const char *

localFileName

)

inlinestatic

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Returns the Unicode version of the given localFileName.

See encodeName() for details.

Definition at line 127 of file qfile.h.

The QByteArray class provides an array of bytes.

static QString decodeName(const QByteArray &localFileName)

This does the reverse of QFile::encodeName() using localFileName.

◆ encodeName()

By default, this function converts fileName to the local 8-bit encoding determined by the user’s locale.

This is sufficient for file names that the user chooses. File names hard-coded into the application should only use 7-bit ASCII filename characters.

See also: decodeName() setEncodingFunction()

Definition at line 528 of file qfile.cpp.

Referenced by QProcessPrivate::_q_notified(), QInotifyFileSystemWatcherEngine::addPaths(), QKqueueFileSystemWatcherEngine::addPaths(), QZipWriter::addSymLink(), QSharedMemoryPrivate::attach(), QSystemSemaphorePrivate::cleanHandle(), QFontEngineQPF::cleanUpAfterClientCrash(), QSharedMemoryPrivate::create(), QProcessPrivate::createChannel(), QFileSystemEngine::createDirectory(), QSharedMemoryPrivate::createUnixKeyFile(), QSharedMemoryPrivate::detach(), QTranslatorPrivate::do_load(), QFileSystemEngine::getLinkTarget(), QSystemSemaphorePrivate::handle(), QSharedMemoryPrivate::handle(), initializeDb(), QLibraryPrivate::isPlugin(), QLibraryPrivate::load_sys(), QFileDialogPrivate::maxNameLength(), QSQLite2Driver::open(), QWSSoundServerPrivate::openFile(), QBasicUnixFontDatabase::populateFontDatabase(), QPlatformFontDatabase::populateFontDatabase(), QFontEngineQPA::QFontEngineQPA(), QFontEngineQPF::QFontEngineQPF(), QFontEngineQPF1::QFontEngineQPF1(), qt_parse_pattern(), registerFont(), QDynamicFileResourceRoot::registerSelf(), QFileSystemEngine::removeDirectory(), QFileSystemEntry::resolveNativeFilePath(), QPluginLoader::setFileName(), QProcessPrivate::startDetached(), and QProcessPrivate::startProcess().

529 {

531 }

QString fileName() const

Returns the name set by setFileName() or to the QFile constructors.

static QFile::EncoderFn encoder

◆ error()

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()

Definition at line 1984 of file qfile.cpp.

Referenced by copy(), QIODevice::errorString(), fontPath(), QPdfBaseEngine::newPage(), QZipReader::QZipReader(), QZipWriter::QZipWriter(), QNetworkAccessFileBackend::readMoreFromFile(), remove(), rename(), and QNetworkDiskCachePrivate::storeItem().

1985 {

1987 return d->error;

1988 }

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

◆ exists() [1/2]

bool QFile::exists

(

)

const

Returns true if the file specified by fileName() exists; otherwise returns false.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

See also: fileName(), setFileName()

Definition at line 626 of file qfile.cpp.

Referenced by QFileDialogPrivate::_q_createDirectory(), QDeclarativeImportDatabase::addImportPath(), QDeclarativeImportDatabase::addPluginPath(), QCoreApplicationPrivate::appendApplicationPathToLibraryPaths(), QNetworkManagerEngine::bytesReceived(), QConnmanEngine::bytesReceived(), QNetworkManagerEngine::bytesWritten(), QConnmanEngine::bytesWritten(), QMacPasteboardMimeVCard::convertFromMime(), copy(), QSharedMemoryPrivate::createUnixKeyFile(), QZipWriter::exists(), QZipReader::exists(), QDir::exists(), QZipReader::extractAll(), QLibraryInfoPrivate::findConfiguration(), fontPath(), QDirectFBPixmapData::fromFile(), QDirectFbBlitterPlatformPixmap::fromFile(), QTransportAuthPrivate::getClientKey(), QGtkStylePrivate::getThemeName(), QSharedMemoryPrivate::handle(), QAxBase::initialize(), initializeDb(), isDirPath(), launchWebBrowser(), QCoreApplication::libraryPaths(), QLibraryPrivate::load_sys(), QFontDatabasePrivate::loadFromCache(), loadSingleEngine(), QNetworkAccessFileBackend::open(), QBasicUnixFontDatabase::populateFontDatabase(), QPlatformFontDatabase::populateFontDatabase(), QIconTheme::QIconTheme(), qmlsqldatabase_open_sync(), QNetworkReplyFileImpl::QNetworkReplyFileImpl(), QDynamicFileResourceRoot::registerSelf(), rename(), QDir::rename(), QNetworkDiskCachePrivate::storeItem(), QConfFileSettingsPrivate::syncConfFile(), QFileDialogPrivate::typedFiles(), and QAxFactory::validateLicenseKey().

627 {

628

631 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

FileFlag

The permissions and types of a file, suitable for OR'ing together.

◆ exists() [2/2]

bool QFile::exists

(

const QString &

fileName

)

static

Returns true if the file specified by fileName exists; otherwise returns false.

Definition at line 639 of file qfile.cpp.

640 {

642 }

bool exists() const

Returns true if the file exists; otherwise returns false.

The QFileInfo class provides system-independent file information.

◆ fileEngine()

Returns the QIOEngine for this QFile object.

Warning: This function is not part of the public interface.

Reimplemented in QTemporaryFile.

Definition at line 1965 of file qfile.cpp.

Referenced by QFontDatabase::addApplicationFont(), copy(), QTemporaryFile::createLocalFile(), exists(), fileName(), QFreetypeFace::getFace(), link(), map(), open(), permissions(), readLink(), remove(), rename(), resize(), setPermissions(), size(), and unmap().

1966 {

1968 if(!d->fileEngine)

1970 return d->fileEngine;

1971 }

static QAbstractFileEngine * create(const QString &fileName)

Creates and returns a QAbstractFileEngine suitable for processing fileName.

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

◆ fileName()

Returns the name set by setFileName() or to the QFile constructors.

See also: setFileName(), QFileInfo::fileName()

Definition at line 470 of file qfile.cpp.

Referenced by __fileOpen(), QMacPasteboardMimeVCard::convertFromMime(), QGraphicsAnchorLayoutPrivate::dumpGraph(), encodeName(), QTextDocumentWriter::fileName(), QImageWriter::fileName(), QImageReader::fileName(), QImageReaderPrivate::initHandler(), QFontDatabasePrivate::loadFromCache(), QTemporaryFile::open(), open(), QIconTheme::QIconTheme(), QIODevice::QIODevice(), QNetworkReplyFileImpl::QNetworkReplyFileImpl(), QCacheItem::read(), registerFont(), QFileInfo::setFile(), setFileName(), and QConfFileSettingsPrivate::syncConfFile().

471 {

473 }

virtual QString fileName(FileName file=DefaultName) const

Return the file engine's current file name in the format specified by file.

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

◆ flush()

Flushes any buffered data to the file.

Returns true if successful; otherwise returns false.

Definition at line 1645 of file qfile.cpp.

Referenced by close(), QTextStreamPrivate::flushWriteBuffer(), registerFont(), QNetworkAccessFileBackend::uploadReadyReadSlot(), and writeData().

1646 {

1648 if (!d->fileEngine) {

1649 qWarning(«QFile::flush: No file engine. Is IODevice open?»);

1650 return false;

1651 }

1652

1653 if (!d->writeBuffer.isEmpty()) {

1659 d->setError(err, d->fileEngine->errorString());

1660 return false;

1661 }

1662 }

1663

1664 if (!d->fileEngine->flush()) {

1668 d->setError(err, d->fileEngine->errorString());

1669 return false;

1670 }

1671 return true;

1672 }

static qint64 _qfile_writeData(QAbstractFileEngine *engine, QRingBuffer *buffer)

Q_CORE_EXPORT void qWarning(const char *,…)

qint64 size() const

Returns the size of the file.

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

FileError

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

◆ handle()

int QFile::handle

(

)

const

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, handle() returns -1.

This function is not supported on Windows CE.

On Symbian, this function returns -1 if the file was opened normally, as Symbian OS native file handles do not fit in an int, and are incompatible with C library functions that the handle would be used for. If the file was opened using the overloads that take an open C library file handle / file descriptor, then this function returns that same handle.

See also: QSocketNotifier

Definition at line 1419 of file qfile.cpp.

Referenced by QTextStreamPrivate::fillReadBuffer(), QPatternist::ColorOutputPrivate::isColoringPossible(), and QConfFileSettingsPrivate::syncConfFile().

1420 {

1422 if (!isOpen() || !d->fileEngine)

1423 return -1;

1424

1425 return d->fileEngine->handle();

1426 }

bool isOpen() const

Returns true if the device is open; otherwise returns false.

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

◆ isSequential()

bool QFile::isSequential

(

)

const

virtual

Returns true if the file can only be manipulated sequentially; otherwise returns false.

Most files support random-access, but some special files may not.

See also: QIODevice::isSequential()

Reimplemented from QIODevice.

Definition at line 1044 of file qfile.cpp.

Referenced by QFilePrivate::putCharHelper(), and rename().

1045 {

1047 return d->fileEngine && d->fileEngine->isSequential();

1048 }

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

◆ link() [1/2]

bool QFile::link

(

const QString &

linkName

)

Creates a link named linkName that points to the file currently specified by fileName().

What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true if successful; otherwise returns false.

This function will not overwrite an already existing entity in the file system; in this case, link() will return false and set QFile::error() to return QFile::RenameError.

Note: To create a valid link on Windows, linkName must have a .lnk file extension.; Symbian filesystem does not support links.

See also: setFileName()

Definition at line 877 of file qfile.cpp.

Referenced by QDirModel::dropMimeData(), QFileSystemModel::dropMimeData(), and QZipReader::extractAll().

878 {

880 if (d->fileName.isEmpty()) {

881 qWarning(«QFile::link: Empty or null file name»);

882 return false;

883 }

887 return true;

888 }

890 return false;

891 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

Q_CORE_EXPORT void qWarning(const char *,…)

void unsetError()

Sets the file's error to QFile::NoError.

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

The QFileInfo class provides system-independent file information.

bool link(const QString &newName)

Creates a link named linkName that points to the file currently specified by fileName().

◆ link() [2/2]

bool QFile::link	(	const QString &	fileName,
		const QString &	linkName
	)

static

Creates a link named linkName that points to the file fileName.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true if successful; otherwise returns false.

See also: link()

Definition at line 908 of file qfile.cpp.

909 {

910 return QFile(fileName).link(linkName);

911 }

◆ map()

Maps size bytes of the file into memory starting at offset.

Since: 4.4 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.

Any mapping options can be passed through flags.

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

Note: On Windows CE 5.0 the file will be closed before mapping occurs.

See also: unmap(), QAbstractFileEngine::supportsExtension()

Definition at line 1460 of file qfile.cpp.

Referenced by QNetworkDiskCache::data(), and qt_parse_pattern().

1461 {

1466 uchar *address = d->fileEngine->map(offset, size, flags);

1467 if (address == 0)

1468 d->setError(d->fileEngine->error(), d->fileEngine->errorString());

1469 return address;

1470 }

1471 return 0;

1472 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

qint64 size() const

Returns the size of the file.

void unsetError()

Sets the file's error to QFile::NoError.

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

◆ open() [1/5]

bool QFile::open

(

OpenMode

mode

)

virtual

Opens the file using OpenMode mode, returning true if successful; otherwise false.

The mode must be QIODevice::ReadOnly, QIODevice::WriteOnly, or QIODevice::ReadWrite. It may also have additional flags, such as QIODevice::Text and QIODevice::Unbuffered.

Note: In QIODevice::WriteOnly or QIODevice::ReadWrite mode, if the relevant file does not already exist, this function will try to create a new file before opening it.

See also: QIODevice::OpenMode, setFileName()

Reimplemented from QIODevice.

Reimplemented in QTemporaryFile.

Definition at line 1064 of file qfile.cpp.

Referenced by __fileOpen(), QFontDatabase::addApplicationFont(), QTransportAuth::authorizeRequest(), QNetworkManagerEngine::bytesReceived(), QConnmanEngine::bytesReceived(), QNetworkManagerEngine::bytesWritten(), QConnmanEngine::bytesWritten(), QUnixPrintWidgetPrivate::checkFields(), QPatternist::ColorOutputPrivate::ColorOutputPrivate(), compileSource(), QGLShader::compileSourceFile(), QMacPasteboardMimeVCard::convertFromMime(), copy(), QTemporaryFile::createLocalFile(), createPixmapDataSync(), QUuid::createUuid(), QNetworkDiskCache::data(), QTranslatorPrivate::do_load(), QGraphicsAnchorLayoutPrivate::dumpGraph(), DumpIDL(), dumpOutput(), QPdfEnginePrivate::embedFont(), QtopiaPrintEngine::end(), QZipReader::extractAll(), QBenchmarkValgrindUtils::extractResult(), QNetworkDiskCache::fileMetaData(), fontFile(), fontPath(), QDirectFBPixmapData::fromFile(), QGLPixmapData::fromFile(), QSslCertificate::fromPath(), QFreetypeFace::getFace(), QGtkStylePrivate::getThemeName(), QImageReader::imageFormat(), QScriptEngine::importExtension(), QDeclarativeInclude::include(), QCss::Parser::init(), QImageReaderPrivate::initHandler(), initializeDb(), QConfFile::isWritable(), launchWebBrowser(), QPicture::load(), QSvgTinyDocument::load(), QDeclarativeBorderImage::load(), QDeclarativeDataLoader::load(), QAxScriptManager::load(), QFontDatabasePrivate::loadFromCache(), QRawFont::loadFromFile(), QWSKbPrivate::loadKeymap(), QTextBrowser::loadResource(), QTextDocument::loadResource(), QScriptDebuggerConsolePrivate::loadScriptedCommands(), QHostInfo::localDomainName(), FAREnforcer::logAuthAttempt(), QNetworkAccessFileBackend::open(), QTemporaryFile::open(), open(), QFileOpenEvent::openFile(), QPdfBaseEnginePrivate::openPrintDevice(), operator<<(), QDeclarativeDirParser::parse(), QPatternist::XsdSchemaParser::parseImport(), QPictureIO::pictureFormat(), QDeclarativePixmapReader::processJob(), QDeclarativeWorkerScriptEnginePrivate::processLoad(), QNetworkReplyFileImpl::QNetworkReplyFileImpl(), qt_getDefaultFromHomePrinters(), qt_getLprPrinters(), qt_parse_pattern(), qt_parseEtcLpPrinters(), qt_parseNsswitchConf(), qt_parsePrintcap(), qt_parsePrintersConf(), qt_parseQconfig(), QTextStream::QTextStream(), QZipReader::QZipReader(), QZipWriter::QZipWriter(), QPictureIO::read(), QWSCalibratedMouseHandler::readCalibration(), readConf(), readSourceFile(), registerFont(), QDynamicFileResourceRoot::registerSelf(), rename(), runningUnderDebugger(), QPicture::save(), QWaylandSelection::send(), QSslSocket::setLocalCertificate(), QSslSocket::setPrivateKey(), QTransportAuth::setProcessKey(), QSslSocketBackendPrivate::startHandshake(), QConfFileSettingsPrivate::syncConfFile(), QDeclarativeInclude::worker_include(), QSvgIconEngine::write(), QPictureIO::write(), QWSCalibratedMouseHandler::writeCalibration(), writeIncludeFile(), QCoreApplicationData::~QCoreApplicationData(), and QTraceWindowSurface::~QTraceWindowSurface().

1065 {

1069 return false;

1070 }

1073

1076 qWarning(«QIODevice::open: File access not specified»);

1077 return false;

1078 }

1079

1080 #ifdef Q_OS_SYMBIAN

1081

1083 #else

1084

1086 #endif

1087 {

1089 if (mode & Append) {

1090

1091

1093 }

1094 return true;

1095 }

1099 d->setError(err, d->fileEngine->errorString());

1100 return false;

1101 }

QString fileName() const

Returns the name set by setFileName() or to the QFile constructors.

bool open(OpenMode flags)

Opens the file using OpenMode mode, returning true if successful; otherwise false.

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

bool isOpen() const

Returns true if the device is open; otherwise returns false.

virtual bool seek(qint64 pos)

Sets the file position to the given offset.

Q_CORE_EXPORT void qWarning(const char *,…)

qint64 size() const

Returns the size of the file.

void unsetError()

Sets the file's error to QFile::NoError.

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

virtual bool open(OpenMode mode)

Opens the device and sets its OpenMode to mode.

FileError

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

#define qPrintable(string)

◆ open() [2/5]

bool QFile::open	(	FILE *	fh,
		OpenMode	mode
	)

Opens the existing file handle fh in the given mode.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

Example:

#include <stdio.h>

void printError(const char* msg)

{

file.write(msg, qstrlen(msg));

}

When a QFile is opened using this function, close() does not actually close the file, but only flushes it.

Warning:

If fh does not refer to a regular file, e.g., it is stdin, stdout, or stderr, you may not be able to seek(). size() returns 0 in those cases. See QIODevice::isSequential() for more information.
Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

Note: For Windows CE you may not be able to call resize().

See also: close(), {qmake Variable Reference::CONFIG}{qmake Variable Reference}

Note for the Windows Platform

fh must be opened in binary mode (i.e., the mode string must contain ‘b’, as in «rb» or «wb») when accessing files and other random-access devices. Qt will translate the end-of-line characters if you pass QIODevice::Text to mode. Sequential devices, such as stdin and stdout, are unaffected by this limitation.

You need to enable support for console applications in order to use the stdin, stdout and stderr streams at the console. To do this, add the following declaration to your application’s project file:

Definition at line 1152 of file qfile.cpp.

1153 {

1155 }

bool open(OpenMode flags)

Opens the file using OpenMode mode, returning true if successful; otherwise false.

◆ open() [3/5]

bool QFile::open	(	int	fd,
		OpenMode	mode
	)

Opens the existing file descriptor fd in the given mode.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

When a QFile is opened using this function, close() does not actually close the file.

The QFile that is opened using this function is automatically set to be in raw mode; this means that the file input/output functions are slow. If you run into performance issues, you should try to use one of the other open functions.

Warning: If fd is not a regular file, e.g, it is 0 (stdin), 1 (stdout), or 2 (stderr), you may not be able to seek(). In those cases, size() returns 0. See QIODevice::isSequential() for more information.; For Windows CE you may not be able to call seek(), setSize(), fileTime(). size() returns 0.; Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

See also: close()

Definition at line 1270 of file qfile.cpp.

1271 {

1273 }

bool open(OpenMode flags)

Opens the file using OpenMode mode, returning true if successful; otherwise false.

◆ open() [4/5]

bool QFile::open	(	FILE *	fh,
		OpenMode	mode,
		FileHandleFlags	handleFlags
	)

Opens the existing file handle fh in the given mode.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

Example:

#include <stdio.h>

void printError(const char* msg)

{

file.write(msg, qstrlen(msg));

}

When a QFile is opened using this function, behaviour of close() is controlled by the AutoCloseHandle flag. If AutoCloseHandle is specified, and this function succeeds, then calling close() closes the adopted handle. Otherwise, close() does not actually close the file, but only flushes it.

Warning:

If fh does not refer to a regular file, e.g., it is stdin, stdout, or stderr, you may not be able to seek(). size() returns 0 in those cases. See QIODevice::isSequential() for more information.
Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

Note: For Windows CE you may not be able to call resize().

See also: close(), {qmake Variable Reference::CONFIG}{qmake Variable Reference}

Note for the Windows Platform

Definition at line 1203 of file qfile.cpp.

1204 {

1208 return false;

1209 }

1214 qWarning(«QFile::open: File access not specified»);

1215 return false;

1216 }

1217 if (d->openExternalFile(mode, fh, handleFlags)) {

1219 if (mode & Append) {

1221 } else {

1223 if (pos != -1)

1225 }

1226 return true;

1227 }

1228 return false;

1229 }

QString fileName() const

Returns the name set by setFileName() or to the QFile constructors.

bool isOpen() const

Returns true if the device is open; otherwise returns false.

Q_CORE_EXPORT void qWarning(const char *,…)

qint64 pos() const

Reimplemented Function

qint64 size() const

Returns the size of the file.

void unsetError()

Sets the file's error to QFile::NoError.

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

virtual bool open(OpenMode mode)

Opens the device and sets its OpenMode to mode.

#define qPrintable(string)

bool seek(qint64 offset)

For random-access devices, this function sets the current position to pos, returning true on success…

◆ open() [5/5]

bool QFile::open	(	int	fd,
		OpenMode	mode,
		FileHandleFlags	handleFlags
	)

Opens the existing file descriptor fd in the given mode.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

When a QFile is opened using this function, behaviour of close() is controlled by the handleFlags argument. If AutoCloseHandle is specified, and this function succeeds, then calling close() closes the adopted handle. Otherwise, close() does not actually close the file, but only flushes it.

Warning: If fd is not a regular file, e.g, it is 0 (stdin), 1 (stdout), or 2 (stderr), you may not be able to seek(). In those cases, size() returns 0. See QIODevice::isSequential() for more information.; For Windows CE you may not be able to call seek(), setSize(), fileTime(). size() returns 0.; Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

See also: close()

Definition at line 1308 of file qfile.cpp.

1309 {

1313 return false;

1314 }

1319 qWarning(«QFile::open: File access not specified»);

1320 return false;

1321 }

1322 if (d->openExternalFile(mode, fd, handleFlags)) {

1324 if (mode & Append) {

1326 } else {

1327 qint64 pos = (qint64)QT_LSEEK(fd, QT_OFF_T(0), SEEK_CUR);

1328 if (pos != -1)

1330 }

1331 return true;

1332 }

1333 return false;

1334 }

QString fileName() const

Returns the name set by setFileName() or to the QFile constructors.

bool isOpen() const

Returns true if the device is open; otherwise returns false.

Q_CORE_EXPORT void qWarning(const char *,…)

qint64 pos() const

Reimplemented Function

qint64 size() const

Returns the size of the file.

void unsetError()

Sets the file's error to QFile::NoError.

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

virtual bool open(OpenMode mode)

Opens the device and sets its OpenMode to mode.

#define qPrintable(string)

bool seek(qint64 offset)

For random-access devices, this function sets the current position to pos, returning true on success…

◆ permissions() [1/2]

QFile::Permissions QFile::permissions

(

)

const

◆ permissions() [2/2]

QFile::Permissions QFile::permissions

(

const QString &

fileName

)

static

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

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 1591 of file qfile.cpp.

1592 {

1593 return QFile(fileName).permissions();

1594 }

◆ pos()

qint64 QFile::pos

(

)

const

virtual

◆ readData()

qint64 QFile::readData	(	char *	data,
		qint64	maxlen
	)

protectedvirtual

Reimplemented Function

Implements QIODevice.

Definition at line 1839 of file qfile.cpp.

1840 {

1843 if (!d->ensureFlushed())

1844 return -1;

1845

1847 if(read < 0) {

1851 d->setError(err, d->fileEngine->errorString());

1852 }

1853

1854 if (read < len) {

1855

1856 d->cachedSize = 0;

1857 }

1858

1859 return read;

1860 }

qint64 read(char *data, qint64 maxlen)

Reads at most maxSize bytes from the device into data, and returns the number of bytes read…

static const char * data(const QByteArray &arr)

void unsetError()

Sets the file's error to QFile::NoError.

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

FileError

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

◆ readLineData()

qint64 QFile::readLineData	(	char *	data,
		qint64	maxlen
	)

protectedvirtual

Reimplemented Function

Reimplemented from QIODevice.

Definition at line 1812 of file qfile.cpp.

1813 {

1815 if (!d->ensureFlushed())

1816 return -1;

1817

1820 read = d->fileEngine->readLine(data, maxlen);

1821 } else {

1822

1823

1825 }

1826

1827 if (read < maxlen) {

1828

1829 d->cachedSize = 0;

1830 }

1831

1832 return read;

1833 }

virtual qint64 readLineData(char *data, qint64 maxlen)

Reads up to maxSize characters into data and returns the number of characters read.

qint64 read(char *data, qint64 maxlen)

Reads at most maxSize bytes from the device into data, and returns the number of bytes read…

static const char * data(const QByteArray &arr)

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

◆ readLink() [1/2]

Use symLinkTarget() instead.

Definition at line 671 of file qfile.cpp.

672 {

674 }

virtual QString fileName(FileName file=DefaultName) const

Return the file engine's current file name in the format specified by file.

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

◆ readLink() [2/2]

Use symLinkTarget() instead.

Definition at line 700 of file qfile.cpp.

701 {

703 }

QString readLink() const

Use symLinkTarget() instead.

The QFileInfo class provides system-independent file information.

◆ remove() [1/2]

Removes the file specified by fileName().

Returns true if successful; otherwise returns false.

The file is closed before it is removed.

See also: setFileName()

Definition at line 715 of file qfile.cpp.

Referenced by QUnixPrintWidgetPrivate::checkFields(), QSystemSemaphorePrivate::cleanHandle(), QBenchmarkValgrindUtils::cleanup(), QFontEngineQPF::cleanUpAfterClientCrash(), QWSServerPrivate::cleanupFonts(), QPdfBaseEnginePrivate::closePrintDevice(), QSharedMemoryPrivate::create(), QSharedMemoryPrivate::detach(), QDirModel::dropMimeData(), DumpIDL(), QNetworkDiskCache::expire(), initializeDb(), QTransportAuth::isDiscoveryMode(), registerFont(), QFileSystemModel::remove(), QDir::remove(), QNetworkDiskCachePrivate::removeFile(), rename(), and QNetworkDiskCachePrivate::storeItem().

716 {

718 if (d->fileName.isEmpty()) {

719 qWarning(«QFile::remove: Empty or null file name»);

720 return false;

721 }

727 return true;

728 }

730 }

731 return false;

732 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

Q_CORE_EXPORT void qWarning(const char *,…)

void unsetError()

Sets the file's error to QFile::NoError.

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

FileError error() const

Returns the file error status.

virtual void close()

Calls QFile::flush() and closes the file.

◆ remove() [2/2]

bool QFile::remove

(

const QString &

fileName

)

static

Removes the file specified by the fileName given.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

See also: remove()

Definition at line 748 of file qfile.cpp.

749 {

750 return QFile(fileName).remove();

751 }

◆ rename() [1/2]

bool QFile::rename

(

const QString &

newName

)

Renames the file currently specified by fileName() to newName.

Returns true if successful; otherwise returns false.

If a file with the name newName already exists, rename() returns false (i.e., QFile will not overwrite it).

The file is closed before it is renamed.

See also: setFileName()

Definition at line 766 of file qfile.cpp.

Referenced by QDragManager::drag(), QFileSystemModel::dropMimeData(), initializeDb(), QDir::rename(), and QNetworkDiskCachePrivate::storeItem().

767 {

769 if (d->fileName.isEmpty()) {

770 qWarning(«QFile::rename: Empty or null file name»);

771 return false;

772 }

774

775

776

778 return false;

779 }

785

786 d->fileEngine->setFileName(newName);

787 d->fileName = newName;

788 return true;

789 }

790

792 d->setError(QFile::RenameError, tr(«Will not rename sequential file using block copy»));

793 return false;

794 }

795

796 QFile out(newName);

799 bool error = false;

800 char block[4096];

802 while ((bytes = read(block, sizeof(block))) > 0) {

803 if (bytes != out.write(block, bytes)) {

805 error = true;

806 break;

807 }

808 }

809 if (bytes == -1) {

811 error = true;

812 }

813 if(!error) {

814 if (!remove()) {

816 error = true;

817 }

818 }

819 if (error) {

820 out.remove();

821 } else {

822 d->fileEngine->setFileName(newName);

826 }

829 }

831 }

833 }

834 return false;

835 }

bool rename(const QString &newName)

Renames the file currently specified by fileName() to newName.

bool isSequential() const

Returns true if the file can only be manipulated sequentially; otherwise returns false.

bool open(OpenMode flags)

Opens the file using OpenMode mode, returning true if successful; otherwise false.

QString errorString() const

Returns a human-readable description of the last device error that occurred.

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

static QString tr(const char *sourceText, const char *comment=0, int n=-1)

qint64 read(char *data, qint64 maxlen)

Reads at most maxSize bytes from the device into data, and returns the number of bytes read…

bool exists() const

Returns true if the file specified by fileName() exists; otherwise returns false. …

Q_CORE_EXPORT void qWarning(const char *,…)

void unsetError()

Sets the file's error to QFile::NoError.

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

bool setPermissions(Permissions permissionSpec)

Sets the permissions for the file to the permissions specified.

Permissions permissions() const

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

FileError error() const

Returns the file error status.

virtual void close()

Calls QFile::flush() and closes the file.

void setFileName(const QString &name)

Sets the name of the file.

◆ rename() [2/2]

bool QFile::rename	(	const QString &	oldName,
		const QString &	newName
	)

static

Renames the file oldName to newName.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns true if successful; otherwise returns false.

If a file with the name newName already exists, rename() returns false (i.e., QFile will not overwrite it).

See also: rename()

Definition at line 853 of file qfile.cpp.

854 {

855 return QFile(oldName).rename(newName);

856 }

◆ resize() [1/2]

bool QFile::resize

(

qint64

)

Sets the file size (in bytes) sz.

Returns true if the file 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.

See also: size(), setFileName()

Definition at line 1528 of file qfile.cpp.

Referenced by QFSFileEnginePrivate::longFileName(), and QConfFileSettingsPrivate::syncConfFile().

1529 {

1531 if (!d->ensureFlushed())

1532 return false;

1534 if (isOpen() && d->fileEngine->pos() > sz)

1536 if(d->fileEngine->setSize(sz)) {

1538 d->cachedSize = sz;

1539 return true;

1540 }

1541 d->cachedSize = 0;

1543 return false;

1544 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

bool isOpen() const

Returns true if the device is open; otherwise returns false.

void unsetError()

Sets the file's error to QFile::NoError.

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

bool seek(qint64 offset)

For random-access devices, this function sets the current position to pos, returning true on success…

◆ resize() [2/2]

bool QFile::resize	(	const QString &	fileName,
		qint64	sz
	)

static

Sets fileName to size (in bytes) sz.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

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

See also: resize()

Definition at line 1561 of file qfile.cpp.

1562 {

1563 return QFile(fileName).resize(sz);

1564 }

◆ seek()

bool QFile::seek

(

qint64

pos

)

virtual

For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred.

For sequential devices, the default behavior is to do nothing and return false.

Seeking beyond the end of a file: If the position is beyond the end of a file, then seek() shall not immediately extend the file. If a write is performed at this position, then the file shall be extended. The content of the file between the previous end of file and the newly written data is UNDEFINED and varies between platforms and file systems.

Reimplemented from QIODevice.

Definition at line 1784 of file qfile.cpp.

Referenced by QTemporaryFile::createLocalFile(), QTransportAuthPrivate::getClientKey(), open(), QFilePrivate::putCharHelper(), QPictureIO::read(), resize(), and QConfFileSettingsPrivate::syncConfFile().

1785 {

1788 qWarning(«QFile::seek: IODevice is not open»);

1789 return false;

1790 }

1791

1792 if (off == d->pos && off == d->devicePos)

1793 return true;

1794

1795 if (!d->ensureFlushed())

1796 return false;

1797

1802 d->setError(err, d->fileEngine->errorString());

1803 return false;

1804 }

1806 return true;

1807 }

bool isOpen() const

Returns true if the device is open; otherwise returns false.

Q_CORE_EXPORT void qWarning(const char *,…)

void unsetError()

Sets the file's error to QFile::NoError.

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

FileError

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

virtual bool seek(qint64 pos)

For random-access devices, this function sets the current position to pos, returning true on success…

◆ setDecodingFunction()

void QFile::setDecodingFunction

(

DecoderFn

function

)

static

Sets the function for decoding 8-bit file names.

Note: This class or function is not reentrant.

The default uses the locale-specific 8-bit encoding.

See also: setEncodingFunction(), decodeName()

Definition at line 606 of file qfile.cpp.

607 {

608 if (!f)

611 }

static QString locale_decode(const QByteArray &f)

static QFile::DecoderFn decoder

◆ setEncodingFunction()

void QFile::setEncodingFunction

(

EncoderFn

function

)

static

Sets the function for encoding Unicode file names.

Note: This class or function is not reentrant.

The default encodes in the locale-specific 8-bit encoding.

See also: encodeName(), setDecodingFunction()

Definition at line 572 of file qfile.cpp.

573 {

574 if (!f)

577 }

static QFile::EncoderFn encoder

static QByteArray locale_encode(const QString &f)

◆ setFileName()

void QFile::setFileName

(

const QString &

name

)

Sets the name of the file.

The name can have no path, a relative path, or an absolute path.

Do not call this function if the file has already been opened.

If the file name has no path or a relative path, the path used will be the application’s current directory path at the time of the open() call.

Example:

Note that the directory separator «/» works for all operating systems supported by Qt.

See also: fileName(), QFileInfo, QDir

Definition at line 494 of file qfile.cpp.

Referenced by QMacPasteboardMimeVCard::convertFromMime(), fontPath(), QImageReaderPrivate::initHandler(), QHostInfo::localDomainName(), QNetworkAccessFileBackend::open(), QFileOpenEvent::openFile(), QIconTheme::QIconTheme(), QNetworkReplyFileImpl::QNetworkReplyFileImpl(), QPictureIO::read(), rename(), and QPictureIO::write().

495 {

498 qWarning(«QFile::setFileName: File (%s) is already opened»,

501 }

502 if(d->fileEngine) {

503 delete d->fileEngine;

504 d->fileEngine = 0;

505 }

506 d->fileName = name;

507 }

QString fileName() const

Returns the name set by setFileName() or to the QFile constructors.

bool isOpen() const

Returns true if the device is open; otherwise returns false.

Q_CORE_EXPORT void qWarning(const char *,…)

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

virtual void close()

Calls QFile::flush() and closes the file.

#define qPrintable(string)

◆ setPermissions() [1/2]

bool QFile::setPermissions

(

Permissions

permissions

)

Sets the permissions for the file to the permissions specified.

Returns true if successful, or false if the permissions cannot be modified.

See also: permissions(), setFileName()

Definition at line 1605 of file qfile.cpp.

Referenced by copy(), QZipReader::extractAll(), rename(), and QConfFileSettingsPrivate::syncConfFile().

1606 {

1610 return true;

1611 }

1613 return false;

1614 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

void unsetError()

Sets the file's error to QFile::NoError.

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

bool setPermissions(Permissions permissionSpec)

Sets the permissions for the file to the permissions specified.

Permissions permissions() const

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

◆ setPermissions() [2/2]

bool QFile::setPermissions	(	const QString &	fileName,
		Permissions	permissions
	)

static

Sets the permissions for fileName file to permissions.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 1626 of file qfile.cpp.

1627 {

1629 }

Permissions permissions() const

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

◆ size()

qint64 QFile::size

(

)

const

virtual

Returns the size of the file.

For regular empty files on Unix (e.g. those in /proc), this function returns 0; the contents of such a file are generated on demand in response to you calling read().

Reimplemented from QIODevice.

Definition at line 1707 of file qfile.cpp.

Referenced by copy(), QNetworkDiskCache::data(), QTranslatorPrivate::do_load(), QNetworkDiskCache::expire(), flush(), open(), qt_parse_pattern(), QDynamicFileResourceRoot::registerSelf(), QCacheItem::size(), and QNetworkDiskCachePrivate::storeItem().

1708 {

1710 if (!d->ensureFlushed())

1711 return 0;

1713 return d->cachedSize;

1714 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

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

virtual qint64 size() const

Returns the size of the file.

◆ symLinkTarget() [1/2]

QString QFile::symLinkTarget

(

)

const

inline

Returns the absolute path of the file or directory a symlink (or shortcut on Windows) points to, or a an empty string if the object isn’t a symbolic link.

Since: 4.2 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

This name may not represent an existing file; it is only a string. QFile::exists() returns true if the symlink points to an existing file.

See also: fileName() setFileName()

Definition at line 137 of file qfile.h.

QString readLink() const

Use symLinkTarget() instead.

◆ symLinkTarget() [2/2]

static QString QFile::symLinkTarget

(

const QString &

fileName

)

inlinestatic

Returns the absolute path of the file or directory referred to by the symlink (or shortcut on Windows) specified by fileName, or returns an empty string if the fileName does not correspond to a symbolic link.

Since: 4.2

This name may not represent an existing file; it is only a string. QFile::exists() returns true if the symlink points to an existing file.

Definition at line 138 of file qfile.h.

138 { return readLink(fileName); }

QString readLink() const

Use symLinkTarget() instead.

◆ unmap()

bool QFile::unmap

(

uchar *

address

)

Unmaps the memory address.

Since: 4.4

Returns true if the unmap succeeds; false otherwise.

See also: map(), QAbstractFileEngine::supportsExtension()

Definition at line 1485 of file qfile.cpp.

1486 {

1491 bool success = d->fileEngine->unmap(address);

1492 if (!success)

1493 d->setError(d->fileEngine->error(), d->fileEngine->errorString());

1494 return success;

1495 }

1496 d->setError(PermissionsError, tr(«No file engine available or engine does not support UnMapExtension»));

1497 return false;

1498 }

virtual QAbstractFileEngine * fileEngine() const

Returns the QIOEngine for this QFile object.

static QString tr(const char *sourceText, const char *comment=0, int n=-1)

void unsetError()

Sets the file's error to QFile::NoError.

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

◆ unsetError()

void QFile::unsetError

(

)

Sets the file’s error to QFile::NoError.

See also: error()

Definition at line 1996 of file qfile.cpp.

Referenced by close(), copy(), QIODevice::errorString(), link(), map(), open(), readData(), remove(), rename(), resize(), seek(), setPermissions(), unmap(), and writeData().

1997 {

2000 }

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

◆ writeData()

qint64 QFile::writeData	(	const char *	data,
		qint64	len
	)

protectedvirtual

Reimplemented Function

Implements QIODevice.

Definition at line 1923 of file qfile.cpp.

1924 {

1927 d->lastWasWrite = true;

1928 bool buffered = !(d->openMode & Unbuffered);

1929

1930

1933 return -1;

1934 }

1935

1936

1937

1939 qint64 ret = d->fileEngine->write(data, len);

1940 if(ret < 0) {

1944 d->setError(err, d->fileEngine->errorString());

1945 }

1946 return ret;

1947 }

1948

1949

1950 char *writePointer = d->writeBuffer.reserve(len);

1951 if (len == 1)

1952 *writePointer = *data;

1953 else

1954 ::memcpy(writePointer, data, len);

1955 return len;

1956 }

bool flush()

Flushes any buffered data to the file.

static const char * data(const QByteArray &arr)

static const int QFILE_WRITEBUFFER_SIZE

void unsetError()

Sets the file's error to QFile::NoError.

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

FileError

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

The documentation for this class was generated from the following files:

/src/corelib/io/qfile.h
/src/corelib/io/qfile.cpp

Источник

The QFile class provides an interface for reading from and writing to files. More…

Member Function Documentation

QFile::QFile ( const QString & name )

Constructs a new file object to represent the file with the given name.

QFile::QFile ( QObject * parent )

Constructs a new file object with the given parent.

QFile::QFile ( const QString & name, QObject * parent )

Constructs a new file object with the given parent to represent the file with the specified name.

QFile::~QFile ()

Destroys the file object, closing it if necessary.

bool QFile::atEnd () const [virtual]

Reimplemented from QIODevice::atEnd().

Returns true if the end of the file has been reached; otherwise returns false.

For regular empty files on Unix (e.g. those in /proc), this function returns true, since the file system reports that the size of such a file is 0. Therefore, you should not depend on atEnd() when reading data from such a file, but rather call read() until no more data can be read.

void QFile::close () [virtual]

Reimplemented from QIODevice::close().

Calls QFile::flush() and closes the file. Errors from flush are ignored.

See also QIODevice::close().

bool QFile::copy ( const QString & newName )

Copies the file currently specified by fileName() to a file called newName. Returns true if successful; otherwise returns false.

Note that if a file with the name newName already exists, copy() returns false (i.e. QFile will not overwrite it).

The source file is closed before it is copied.

See also setFileName().

bool QFile::copy ( const QString & fileName, const QString & newName ) [static]

This is an overloaded function.

Copies the file fileName to newName. Returns true if successful; otherwise returns false.

If a file with the name newName already exists, copy() returns false (i.e., QFile will not overwrite it).

See also rename().

QString QFile::decodeName ( const QByteArray & localFileName ) [static]

This does the reverse of QFile::encodeName() using localFileName.

See also setDecodingFunction() and encodeName().

QString QFile::decodeName ( const char * localFileName ) [static]

This is an overloaded function.

Returns the Unicode version of the given localFileName. See encodeName() for details.

QByteArray QFile::encodeName ( const QString & fileName ) [static]

By default, this function converts fileName to the local 8-bit encoding determined by the user’s locale. This is sufficient for file names that the user chooses. File names hard-coded into the application should only use 7-bit ASCII filename characters.

See also decodeName() and setEncodingFunction().

FileError QFile::error () const

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().

bool QFile::exists ( const QString & fileName ) [static]

Returns true if the file specified by fileName exists; otherwise returns false.

bool QFile::exists () const

This is an overloaded function.

Returns true if the file specified by fileName() exists; otherwise returns false.

See also fileName() and setFileName().

QString QFile::fileName () const

Returns the name set by setFileName() or to the QFile constructors.

See also setFileName() and QFileInfo::fileName().

bool QFile::flush ()

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

int QFile::handle () const

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, handle() returns -1.

This function is not supported on Windows CE.

On Symbian, this function returns -1 if the file was opened normally, as Symbian OS native file handles do not fit in an int, and are incompatible with C library functions that the handle would be used for. If the file was opened using the overloads that take an open C library file handle / file descriptor, then this function returns that same handle.

See also QSocketNotifier.

bool QFile::isSequential () const [virtual]

Reimplemented from QIODevice::isSequential().

Returns true if the file can only be manipulated sequentially; otherwise returns false.

Most files support random-access, but some special files may not.

See also QIODevice::isSequential().

bool QFile::link ( const QString & linkName )

Creates a link named linkName that points to the file currently specified by fileName(). What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true if successful; otherwise returns false.

This function will not overwrite an already existing entity in the file system; in this case, link() will return false and set error() to return RenameError.

Note: To create a valid link on Windows, linkName must have a .lnk file extension.

Note: Symbian filesystem does not support links.

See also setFileName().

bool QFile::link ( const QString & fileName, const QString & linkName ) [static]

This is an overloaded function.

Creates a link named linkName that points to the file fileName. What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true if successful; otherwise returns false.

See also link().

uchar * QFile::map ( qint64 offset, qint64 size, MemoryMapFlags flags = NoOptions )

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.

Any mapping options can be passed through flags.

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

Note: On Windows CE 5.0 the file will be closed before mapping occurs.

This function was introduced in Qt 4.4.

See also unmap() and QAbstractFileEngine::supportsExtension().

bool QFile::open ( OpenMode mode ) [virtual]

Reimplemented from QIODevice::open().

Opens the file using OpenMode mode, returning true if successful; otherwise false.

The mode must be QIODevice::ReadOnly, QIODevice::WriteOnly, or QIODevice::ReadWrite. It may also have additional flags, such as QIODevice::Text and QIODevice::Unbuffered.

Note: In WriteOnly or ReadWrite mode, if the relevant file does not already exist, this function will try to create a new file before opening it.

See also QIODevice::OpenMode and setFileName().

bool QFile::open ( FILE * fh, OpenMode mode )

This is an overloaded function.

Opens the existing file handle fh in the given mode. Returns true if successful; otherwise returns false.

Example:

 #include <stdio.h>

 void printError(const char* msg)
 {
     QFile file;
     file.open(stderr, QIODevice::WriteOnly);
     file.write(msg, qstrlen(msg));        
     file.close();
 }

When a QFile is opened using this function, close() does not actually close the file, but only flushes it.

Warning:

If fh does not refer to a regular file, e.g., it is stdin, stdout, or stderr, you may not be able to seek(). size() returns 0 in those cases. See QIODevice::isSequential() for more information.
Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

Note: For Windows CE you may not be able to call resize().

Note for the Windows Platform

 CONFIG += console

See also close() and qmake Variable Reference.

bool QFile::open ( FILE * fh, OpenMode mode, FileHandleFlags handleFlags )

This is an overloaded function.

Opens the existing file handle fh in the given mode. Returns true if successful; otherwise returns false.

Example:

 #include <stdio.h>

 void printError(const char* msg)
 {
     QFile file;
     file.open(stderr, QIODevice::WriteOnly);
     file.write(msg, qstrlen(msg));        
     file.close();
 }

Warning:

If fh does not refer to a regular file, e.g., it is stdin, stdout, or stderr, you may not be able to seek(). size() returns 0 in those cases. See QIODevice::isSequential() for more information.
Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

Note: For Windows CE you may not be able to call resize().

Note for the Windows Platform

 CONFIG += console

See also close() and qmake Variable Reference.

bool QFile::open ( int fd, OpenMode mode )

This is an overloaded function.

Opens the existing file descriptor fd in the given mode. Returns true if successful; otherwise returns false.

When a QFile is opened using this function, close() does not actually close the file.

Warning: If fd is not a regular file, e.g, it is 0 (stdin), 1 (stdout), or 2 (stderr), you may not be able to seek(). In those cases, size() returns 0. See QIODevice::isSequential() for more information.

Warning: For Windows CE you may not be able to call seek(), setSize(), fileTime(). size() returns 0.

Warning: Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

See also close().

bool QFile::open ( int fd, OpenMode mode, FileHandleFlags handleFlags )

This is an overloaded function.

Opens the existing file descriptor fd in the given mode. Returns true if successful; otherwise returns false.

Warning: For Windows CE you may not be able to call seek(), setSize(), fileTime(). size() returns 0.

Warning: Since this function opens the file without specifying the file name, you cannot use this QFile with a QFileInfo.

See also close().

bool QFile::open ( const RFile & f, OpenMode mode, FileHandleFlags handleFlags = DontCloseHandle )

This is an overloaded function.

Opens the existing file object f in the given mode. Returns true if successful; otherwise returns false.

Warning: If the file handle is adopted from another process, you may not be able to use this QFile with a QFileInfo.

See also close().

Permissions QFile::permissions () const

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

See also setPermissions() and setFileName().

Permissions QFile::permissions ( const QString & fileName ) [static]

This is an overloaded function.

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

qint64 QFile::pos () const [virtual]

Reimplemented from QIODevice::pos().

qint64 QFile::readData ( char * data, qint64 len ) [virtual protected]

Reimplemented from QIODevice::readData().

qint64 QFile::readLineData ( char * data, qint64 maxlen ) [virtual protected]

Reimplemented from QIODevice::readLineData().

bool QFile::remove ()

Removes the file specified by fileName(). Returns true if successful; otherwise returns false.

The file is closed before it is removed.

See also setFileName().

bool QFile::remove ( const QString & fileName ) [static]

This is an overloaded function.

Removes the file specified by the fileName given.

Returns true if successful; otherwise returns false.

See also remove().

bool QFile::rename ( const QString & newName )

Renames the file currently specified by fileName() to newName. Returns true if successful; otherwise returns false.

If a file with the name newName already exists, rename() returns false (i.e., QFile will not overwrite it).

The file is closed before it is renamed.

See also setFileName().

bool QFile::rename ( const QString & oldName, const QString & newName ) [static]

This is an overloaded function.

Renames the file oldName to newName. Returns true if successful; otherwise returns false.

If a file with the name newName already exists, rename() returns false (i.e., QFile will not overwrite it).

See also rename().

bool QFile::resize ( qint64 sz )

Sets the file size (in bytes) sz. Returns true if the file 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.

See also size() and setFileName().

bool QFile::resize ( const QString & fileName, qint64 sz ) [static]

This is an overloaded function.

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

See also resize().

bool QFile::seek ( qint64 pos ) [virtual]

Reimplemented from QIODevice::seek().

For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred. For sequential devices, the default behavior is to do nothing and return false.

Seeking beyond the end of a file: If the position is beyond the end of a file, then seek() shall not immediately extend the file. If a write is performed at this position, then the file shall be extended. The content of the file between the previous end of file and the newly written data is UNDEFINED and varies between platforms and file systems.

void QFile::setDecodingFunction ( DecoderFn function ) [static]

Sets the function for decoding 8-bit file names. The default uses the locale-specific 8-bit encoding.

Warning: This function is not reentrant.

See also setEncodingFunction() and decodeName().

void QFile::setEncodingFunction ( EncoderFn function ) [static]

Sets the function for encoding Unicode file names. The default encodes in the locale-specific 8-bit encoding.

Warning: This function is not reentrant.

See also encodeName() and setDecodingFunction().

void QFile::setFileName ( const QString & name )

Sets the name of the file. The name can have no path, a relative path, or an absolute path.

Do not call this function if the file has already been opened.

If the file name has no path or a relative path, the path used will be the application’s current directory path at the time of the open() call.

Example:

 QFile file;
 QDir::setCurrent("/tmp");
 file.setFileName("readme.txt");
 QDir::setCurrent("/home");
 file.open(QIODevice::ReadOnly);

Note that the directory separator «/» works for all operating systems supported by Qt.

See also fileName(), QFileInfo, and QDir.

bool QFile::setPermissions ( Permissions permissions )

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

See also permissions() and setFileName().

bool QFile::setPermissions ( const QString & fileName, Permissions permissions ) [static]

This is an overloaded function.

Sets the permissions for fileName file to permissions.

qint64 QFile::size () const [virtual]

Reimplemented from QIODevice::size().

Returns the size of the file.

For regular empty files on Unix (e.g. those in /proc), this function returns 0; the contents of such a file are generated on demand in response to you calling read().

QString QFile::symLinkTarget ( const QString & fileName ) [static]

Returns the absolute path of the file or directory referred to by the symlink (or shortcut on Windows) specified by fileName, or returns an empty string if the fileName does not correspond to a symbolic link.

This name may not represent an existing file; it is only a string. QFile::exists() returns true if the symlink points to an existing file.

This function was introduced in Qt 4.2.

QString QFile::symLinkTarget () const

This is an overloaded function.

Returns the absolute path of the file or directory a symlink (or shortcut on Windows) points to, or a an empty string if the object isn’t a symbolic link.

This name may not represent an existing file; it is only a string. QFile::exists() returns true if the symlink points to an existing file.

This function was introduced in Qt 4.2.

See also fileName() and setFileName().

bool QFile::unmap ( uchar * address )

Unmaps the memory address.

Returns true if the unmap succeeds; false otherwise.

This function was introduced in Qt 4.4.

See also map() and QAbstractFileEngine::supportsExtension().

void QFile::unsetError ()

Sets the file’s error to QFile::NoError.

See also error().

qint64 QFile::writeData ( const char * data, qint64 len ) [virtual protected]

Reimplemented from QIODevice::writeData().

Источник

Автор

Тема: Как получить код ошибки? (Прочитано 5614 раз)

AVDEY

Гость

Начал разбираться с Qt, и не обнаружил аналога функции GetLastError();
Например при работе с файлом.
Функция bool QFile::open(…); возвращает фалсе
я нашел что могу получить QFile::error(); — которая возвращает 15 вариантов ошибки
QFile::errorString(); -возвращает текстовою информацию об ошибке

Так вот функция error() возвращает OpenError = 5
а errorString(); может вернуть: файл не найден, процесс не может получить доступ к файлу. и т. д.

Как получить код ошибки?

С практики программирования на MVC++6.0 функция GetLastError(); использовалась часто, так как получив код ошибки можно предпринять какие то действия без участия пользователя, и это касается не только QFile.


	Записан

kuzulis

Я не распарсил


	Записан

ArchLinux x86_64 / Win10 64 bit

Странник

Гость

в данном случае при OpenError наличие файла вы можете проверить с помощью exists.


	Записан

AVDEY

Гость

в данном случае при OpenError наличие файла вы можете проверить с помощью exists.

А если файл занят другим процессом с монопольным доступом?

Я просто к тому что программа различает тип ошибки судя с вызова функции errorString(); как получить ее цифровой эквивалент как GetLastError();

Да не нужно привязываться к открытию файла, я просто привел пример. Ситуация когда нужно знать код ошибки и что то автоматом переделать а не просто вывести errorString(); возникает не только при работе с фалами.


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LisandreL

Птица говорун

Offline Offline

Сообщений: 984

Надо улыбаться

QFile::error() и возвращает код ошибки. Более детализированного нет. Можно конечно вызывать нативные функции системы (тот же GetLastError) но надо понимать, что в разных ОС коды ошибок будут зачастую не совпадать.


	Записан

AVDEY

Гость

Просто QFile::error() возвращает очень обширно, типа не открыл, не прочитал, не записал, не переименовал и т. д.
а почему не знает, зато детально это знает функция QFile::errorString() но в текстовом виде, поэтому и есть мысль что должен быть цифровой эквивалент QFile::errorString().


	Записан

Странник

Гость

а если файл занят другим процессом, то file.exists() && (file.error() == QFile::OpenError). на отказ в доступе вроде бы отдельный код ошибки был. я это к тому, что мне всегда стандартных кодов хватало. а их малое число, подозреваю, обусловлено кросплатформенностью библиотеки. если в вашем случае и в самом деле недостаточно конкретно — используйте API целевых платформ.


« Последнее редактирование: Март 04, 2012, 20:19 от Странник »	Записан

AVDEY

Гость

я это к тому, что мне всегда стандартных кодов хватало.

К примеру делаем QFile::rename (перемещаем файл) error возвращает ошибку RenameError = 10,
и какие дальнейшие действия файл уже существует, исходный файл занят, недостаточно места на диске и. т. д.
Можно конечно проверить открывается ли файл, существует ли файл с заданным именем в директории назначения проверить свободное место на диске и размер файла, но как по мне уж очень много лишних действий надо делать тем болеее (опять повторюсь) QFile::errorString() различает ошибки. На одну ошибку error несколько стрингових объяснений. (файл не существует, не найден путь к файлу, файл занят другим процессом, файл назначения уже существует)


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Авварон

Никогда не понимал «пост» обработки — сначала попытаться что-то сделать, а потом разбираться, что же именно не получилось. И не важно, разбираем ли мы код ошибки, коих миллион, или ловим эксепшн.
Если разбор ошибки не нужен, то булки в качестве возвращаемого значения достаточно.
Если разбор ошибки нужен, то нет никакой разницы — проверить до вызова действия существует ли файл, или отловить эксепшн «file exists». Тем более, что этих ошибок не так много (йа писал копир файлов, йа знаю).
Ну и хз, каких вам там ошибок не хватает у QFile’а — вроде невалидные параметры в него сложно передать, в отличие от винапи.


	Записан

AVDEY

Гость

… или отловить эксепшн «file exists». …

я не очень еще силен в Qt — не понял что вы имели ввиду.

Предположим ситуацию: исходный файл существует и доступен для чтения, его требуется переместить, в директории назначения файл уже существует с таким же именем но он занят другим процессом file.exists() вернет QFile::OpenError то есть можно предположить что файла нет, а в то же время при перемещении получим ошибку.


	Записан

Авварон

я не очень еще силен в Qt — не понял что вы имели ввиду.

Я в общем слцчаеговорил, не привязываясь к Qt.

Ну проверьте существование и права — если они нормальны, то скорее всего файл занят. И есть мнение что обработать ошибку открытия можно лишь 1м способом, независимо от того, чем эта ошибка вызвана — ничего не делать:)


	Записан

Странник

Гость

И есть мнение что обработать ошибку открытия можно лишь 1м способом, независимо от того, чем эта ошибка вызвана — ничего не делать:)

это в общем случае. но существуют и частные.


	Записан

Источник

QFile Class Reference[QtCore module]

Types

Methods

Static Methods

Detailed Description

Reading Files Directly

Using Streams to Read Files

Signals

Platform Specific Issues

Type Documentation

QFile.FileError

QFile.FileHandleFlag

QFile.MemoryMapFlags

QFile.Permission

Method Documentation

QFile.__init__ (self)

QFile.__init__ (self, QString name)

QFile.__init__ (self, QObject parent)

QFile.__init__ (self, QString name, QObject parent)

bool QFile.atEnd (self)

QFile.close (self)

bool QFile.copy (self, QString newName)

bool QFile.copy (QString fileName, QString newName)

QString QFile.decodeName (QByteArray localFileName)

QString QFile.decodeName (str localFileName)

QByteArray QFile.encodeName (QString fileName)

FileError QFile.error (self)

bool QFile.exists (self)

bool QFile.exists (QString fileName)

QAbstractFileEngine QFile.fileEngine (self)

QString QFile.fileName (self)

bool QFile.flush (self)

int QFile.handle (self)

bool QFile.isSequential (self)

bool QFile.link (self, QString newName)

bool QFile.link (QString oldname, QString newName)

sip.voidptr QFile.map (self, int offset, int size, MemoryMapFlags flags = QFile.NoOptions)

bool QFile.open (self, QIODevice.OpenMode flags)

bool QFile.open (self, int fd, QIODevice.OpenMode flags)

bool QFile.open (self, int fd, QIODevice.OpenMode flags, FileHandleFlags handleFlags)

Permissions QFile.permissions (self)

Permissions QFile.permissions (QString filename)

int QFile.pos (self)

str QFile.readData (self, int maxlen)

str QFile.readLineData (self, int maxlen)

QString QFile.readLink (self)

QString QFile.readLink (QString fileName)

bool QFile.remove (self)

bool QFile.remove (QString fileName)

bool QFile.rename (self, QString newName)

bool QFile.rename (QString oldName, QString newName)

bool QFile.resize (self, int sz)

bool QFile.resize (QString filename, int sz)

bool QFile.seek (self, int offset)

QFile.setFileName (self, QString name)

bool QFile.setPermissions (self, Permissions permissionSpec)

bool QFile.setPermissions (QString filename, Permissions permissionSpec)

int QFile.size (self)

QString QFile.symLinkTarget (self)

QString QFile.symLinkTarget (QString fileName)

bool QFile.unmap (self, sip.voidptr address)

QFile.unsetError (self)

int QFile.writeData (self, str data)

Public Types

Public Functions

Static Public Functions

Protected Functions

Additional Inherited Members

Reading Files Directly

Using Streams to Read Files

Signals

Platform Specific Issues

◆ DecoderFn

◆ EncoderFn

◆ FileError

◆ FileHandleFlag

◆ MemoryMapFlags

◆ Permission

◆ QFile() [1/5]

◆ QFile() [2/5]

QFile Class Reference
^{^{[QtCore module]}}

QFile.init (self)

QFile.init (self, QString name)

QFile.init (self, QObject parent)

QFile.init (self, QString name, QObject parent)