QFile - I/O device that operates on files

       #include <qfile.h>

       Inherits QIODevice.

   Public Members
       QFile ()
       QFile ( const QString & name )
       ~QFile ()
       QString name () const
       void setName ( const QString & name )
       typedef QCString ( * EncoderFn )( const QString &
           fileName)
       typedef QString ( * DecoderFn )( const QCString &
           localfileName)
       bool exists () const
       bool remove ()
       virtual bool open ( int )
       bool open ( int, FILE * )
       bool open ( int, int )
       virtual void close ()
       virtual void flush ()
       virtual uint size () const
       virtual int at () const
       virtual bool at ( int )
       virtual bool atEnd () const
       virtual int readBlock ( char * data, uint len )
       virtual int readLine ( char * data, uint maxlen )
       int readLine ( QString &, uint maxlen )
       virtual int getch ()
       virtual int putch ( int )
       virtual int ungetch ( int )
       int handle () const

   Static Public Members
       QCString encodeName ( const QString & fileName )
       QString decodeName ( const QCString & localFileName )
       void setEncodingFunction ( EncoderFn )
       void setDecodingFunction ( DecoderFn )
       bool exists ( const QString & fileName )
       bool remove ( const QString & fileName )


DESCRIPTION

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

       QFile is an I/O device for reading and writing binary and
       text files. A QFile may be used by itself (readBlock and
       writeBlock) or by more conveniently using QDataStream or
       QTextStream.

       Here is a code fragment that uses QTextStream to read a

       number.

           QFile f("file.txt");
           if ( f.open(IO_ReadOnly) ) {    // file opened successfully
               QTextStream t( &f );        // use a text stream
               QString s;
               int n = 1;
               while ( !t.eof() ) {        // until end of file...
                   s = t.readLine();       // line of text excluding '\n'
                   printf( "%3d: %s\n", n++, (const char *)s );
               }
               f.close();
           }

       The QFileInfo class holds detailed information about a
       file, such as access permissions, file dates and file
       types.

       The QDir class manages directories and lists of file
       names.

       See also QDataStream and QTextStream.

       Examples: xml/tagreader/tagreader.cpp xml/tagreader


MEMBER FUNCTION DOCUMENTATION


QFile::QFile ()

       Constructs a QFile with no name.


QFile::QFile ( const QString & name )

       Constructs a QFile with a file name name.

       See also setName().


QFile::~QFile ()

       Destructs a QFile. Calls close().


bool QFile::at ( int pos ) [virtual]

       Sets the file index to pos. Returns TRUE if successful,
       otherwise FALSE.

       Example:

           QFile f( "data.bin" );
           f.open( IO_ReadOnly );                      // index set to 0
           f.at( 100 );                                // set index to 100
           f.at( f.at()+50 );                          // set index to 150
           f.at( f.size()-80 );                        // set index to 80 before EOF
           f.close();

       Warning: The result is undefined if the file was opened
       using the IO_Append specifier.


       Reimplemented from QIODevice.


int QFile::at () const [virtual]

       Returns the file index.

       See also size().

       Reimplemented from QIODevice.


bool QFile::atEnd () const [virtual]

       Returns TRUE if the end of file has been reached,
       otherwise FALSE.

       See also size().

       Reimplemented from QIODevice.


void QFile::close () [virtual]

       Closes an open file.

       The file is not closed if it was opened with an existing
       file handle. If the existing file handle is a FILE*, the
       file is flushed. If the existing file handle is an int
       file descriptor, nothing is done to the file.

       Some "write-behind" filesystems may report an unspecified
       error on closing the file. These errors only indicate that
       something may have gone wrong since the previous open().
       In such a case status() reports IO_UnspecifiedError after
       close(), otherwise IO_Ok.

       See also open() and flush().

       Reimplemented from QIODevice.


QString QFile::decodeName ( const QCString & localFileName )

       [static]
       This does the reverse of QFile::encodeName().

       See also setDecodingFunction().


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

       When you use QFile, QFileInfo, and QDir to access the
       filesystem with Qt, you can use Unicode filenames. On
       Unix, these filenames are converted to an 8-bit encoding.
       If you want to do your own file I/O on Unix, you should
       convert the filename using this function. On Windows NT,
       Unicode filenames are supported directly in the filesystem
       and this function should be avoided. On Windows 95, non-
       Latin1 locales are not supported at this time.

       By default, this function converts to the local 8-bit

       sufficient for filenames that the user chooses. Filenames
       hard-coded into the application should only use 7-bit
       ASCII filename characters.

       The conversion scheme can be changed using
       setEncodingFunction(). This might be useful if you wish to
       give the user an option to store in filenames in UTF-8,
       etc., but beware that such filenames would probably then
       be unrecognizable when seen by other programs.

       See also decodeName().


bool QFile::exists () const

       Returns TRUE if this file exists, otherwise FALSE.

       See also name().


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

       Returns TRUE if the file given by fileName exists,
       otherwise FALSE.


void QFile::flush () [virtual]

       Flushes the file buffer to the disk.

       close() also flushes the file buffer.

       Reimplemented from QIODevice.


int QFile::getch () [virtual]

       Reads a single byte/character from the file.

       Returns the byte/character read, or -1 if the end of the
       file has been reached.

       See also putch() and ungetch().

       Reimplemented from QIODevice.


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(), as well as
       with QSocketNotifier.

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

       See also QSocketNotifier.


QString QFile::name () const

       Returns the name set by setName().



bool QFile::open ( int m ) [virtual]

       Opens the file specified by the file name currently set,
       using the mode m. Returns TRUE if successful, otherwise
       FALSE.

       The mode parameter m must be a combination of the
       following flags:

       IO_Raw specified raw (non-buffered) file access.

       IO_ReadOnly opens the file in read-only mode.

       IO_WriteOnly opens the file in write-only mode (and
              truncates).

       IO_ReadWrite opens the file in read/write mode, equivalent
              to (IO_ReadOnly|IO_WriteOnly).

       IO_Append opens the file in append mode. This mode is very
              useful when you want to write something to a log
              file. The file index is set to the end of the file.
              Note that the result is undefined if you position
              the file index manually using at() in append mode.

       IO_Truncate truncates the file.

       IO_Translate enables carriage returns and linefeed
              translation for text files under MS-DOS, Windows
              and OS/2.

       The raw access mode is best when I/O is block-operated
       using 4kB block size or greater. Buffered access works
       better when reading small portions of data at a time.

       Important: When working with buffered files, data may not
       be written to the file at once. Call flush to make sure
       the data is really written.

       Warning: We have experienced problems with some C
       libraries when a buffered file is opened for both reading
       and writing. If a read operation takes place immediately
       after a write operation, the read buffer contains garbage
       data. Worse, the same garbage is written to the file.
       Calling flush() before readBlock() solved this problem.

       If the file does not exist and IO_WriteOnly or
       IO_ReadWrite is specified, it is created.

       Example:

           QFile f1( "/tmp/data.bin" );
           QFile f2( "readme.txt" );

           f2.open( IO_ReadOnly | IO_Translate );

       See also name(), close(), isOpen() and flush().

       Reimplemented from QIODevice.


bool QFile::open ( int m, FILE * f )

       Opens a file in the mode m using an existing file handle
       f. Returns TRUE if successful, otherwise FALSE.

       Example:

           #include <stdio.h>
           void printError( const char* msg )
           {
               QFile f;
               f.open( IO_WriteOnly, stderr );
               f.writeBlock( msg, qstrlen(msg) );      // write to stderr
               f.close();
           }

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

       Warning: If f is stdin, stdout, stderr, you may not be
       able to seek. See QIODevice::isSequentialAccess() for more
       information.

       See also close().


bool QFile::open ( int m, int f )

       Opens a file in the mode m using an existing file
       descriptor f. Returns TRUE if successful, otherwise FALSE.

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

       Warning: If f is one of 0 (stdin), 1 (stdout) or 2
       (stderr), you may not be able to seek. size() is set to
       INT_MAX (in limits.h).

       See also close().


int QFile::putch ( int ch ) [virtual]

       Writes the character ch to the file.

       Returns ch, or -1 if some error occurred.

       See also getch() and ungetch().

       Reimplemented from QIODevice.

       Reads at most len bytes from the file into p and returns
       the number of bytes actually read.

       Returns -1 if a serious error occurred.

       Warning: We have experienced problems with some C
       libraries when a buffered file is opened for both reading
       and writing. If a read operation takes place immediately
       after a write operation, the read buffer contains garbage
       data. Worse, the same garbage is written to the file.
       Calling flush() before readBlock() solved this problem.

       See also writeBlock().

       Reimplemented from QIODevice.


int QFile::readLine ( QString & s, uint maxlen )

       Reads a line of text.

       Reads bytes from the file until end-of-line is reached, or
       up to maxlen bytes, and returns the number of bytes read,
       or -1 in case of error. The terminating newline is not
       stripped.

       This function is efficient only for buffered files. Avoid
       readLine() for files that have been opened with the IO_Raw
       flag.

       Note that the string is read as plain Latin1 bytes, not
       Unicode.

       See also readBlock() and QTextStream::readLine().


int QFile::readLine ( char * p, uint maxlen ) [virtual]

       Reads a line of text.

       Reads bytes from the file until end-of-line is reached, or
       up to maxlen bytes, and returns the number of bytes read,
       or -1 in case of error. The terminating newline is not
       stripped.

       This function is efficient only for buffered files. Avoid
       readLine() for files that have been opened with the IO_Raw
       flag.

       See also readBlock() and QTextStream::readLine().

       Reimplemented from QIODevice.


bool QFile::remove ()

       Removes the file specified by the file name currently set.
       Returns TRUE if successful, otherwise FALSE.



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

       Removes the file fileName. Returns TRUE if successful,
       otherwise FALSE.


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

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

       See also encodeName() and decodeName().


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

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

       See also encodeName().


void QFile::setName ( const QString & name )

       Sets the name of the file. The name can include an
       absolute directory path or it can be a name or a path
       relative to the current directory.

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

       Note that if the name is relative QFile does not associate
       it with the current directory. If you change directory
       before calling open(), open uses the new current
       directory.

       Example:

            QFile f;
            QDir::setCurrent( "/tmp" );
            f.setName( "readme.txt" );
            QDir::setCurrent( "/home" );
            f.open( IO_ReadOnly );        // opens "/home/readme.txt" under UNIX

       Also note that the directory separator '/' works for all
       operating systems supported by Qt.

       See also name(), QFileInfo and QDir.


uint QFile::size () const [virtual]

       Returns the file size.

       See also at().

       Reimplemented from QIODevice.


int QFile::ungetch ( int ch ) [virtual]

       Puts the character ch back into the file and decrements
       the index if it is not zero.

       operation.

       Returns ch, or -1 if some error occurred.

       See also getch() and putch().

       Reimplemented from QIODevice.


int QFile::writeBlock ( const QByteArray & data )

       Reimplemented for internal reasons; the API is not
       affected.


int QFile::writeBlock ( const char * p, uint len ) [virtual]

       Reimplemented for internal reasons; the API is not
       affected.

       Writes len bytes from p to the file and returns the number
       of bytes actually written.

       Returns -1 if a serious error occurred.

       Warning: When working with buffered files, data may not be
       written to the file at once. Call flush() to make sure the
       data is really written.

       See also readBlock().

       Reimplemented from QIODevice.


SEE ALSO

       http://doc.trolltech.com/qfile.html
       http://www.trolltech.com/faq/tech.html


COPYRIGHT

       Copyright 1992-2001 Trolltech AS,
       http://www.trolltech.com.  See the license file included
       in the distribution for a complete license statement.


AUTHOR

       Generated automatically from the source code.


BUGS

       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.  Good bug reports
       make our job much simpler. Thank you.

       In case of content or formattting problems with this
       manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qfile.3qt) and
       the Qt version (2.3.1).


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