Detailed Description
The QFileInfo class provides system-independent file information.
QFileInfo provides information about a file's name and position
(path) in the file system, its access rights and whether it is a
directory or symbolic link, etc. The file's size and last
modified/read times are also available.
A QFileInfo can point to a file with either a relative or an
absolute file path. Absolute file paths begin with the directory
separator "/" (or with a drive specification on Windows). Relative
file names begin with a directory name or a file name and specify
a path relative to the current working directory. An example of an
absolute path is the string "/tmp/quartz". A relative path might
look like "src/fatlib". You can use the function isRelative() to
check whether a QFileInfo is using a relative or an absolute file
path. You can call the function convertToAbs() to convert a
relative QFileInfo's path to an absolute path.
The file that the QFileInfo works on is set in the constructor or
later with setFile(). Use exists() to see if the file exists and
size() to get its size.
To speed up performance, QFileInfo caches information about the
file. Because files can be changed by other users or programs, or
even by other parts of the same program, there is a function that
refreshes the file information: refresh(). If you want to switch
off a QFileInfo's caching and force it to access the file system
every time you request information from it call setCaching(FALSE).
The file's type is obtained with isFile(), isDir() and
isSymLink(). The readLink() function provides the name of the file
the symlink points to.
Elements of the file's name can be extracted with dirPath() and
fileName(). The fileName()'s parts can be extracted with
baseName() and extension().
The file's dates are returned by created(), lastModified() and
lastRead(). Information about the file's access permissions is
obtained with isReadable(), isWritable() and isExecutable(). The
file's ownership is available from owner(), ownerId(), group() and
groupId(). You can examine a file's permissions and ownership in a
single statement using the permission() function.
If you need to read and traverse directories, see the QDir class.
See also Input/Output and Networking.
Member Type Documentation
QFileInfo::PermissionSpec
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.
- QFileInfo::ReadOwner - The file is readable by the owner of the file.
- QFileInfo::WriteOwner - The file is writable by the owner of the file.
- QFileInfo::ExeOwner - The file is executable by the owner of the file.
- QFileInfo::ReadUser - The file is readable by the user.
- QFileInfo::WriteUser - The file is writable by the user.
- QFileInfo::ExeUser - The file is executable by the user.
- QFileInfo::ReadGroup - The file is readable by the group.
- QFileInfo::WriteGroup - The file is writable by the group.
- QFileInfo::ExeGroup - The file is executable by the group.
- QFileInfo::ReadOther - The file is readable by anyone.
- QFileInfo::WriteOther - The file is writable by anyone.
- QFileInfo::ExeOther - The file is executable by anyone.
Warning: The semantics of ReadUser, WriteUser and ExeUser are
unfortunately not platform independent: 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. If you want to
find the rights of the owner of the file, you should use the flags ReadOwner, WriteOwner and ExeOwner. If you want to find out the
rights of the current user, you should use isReadable(), isWritable() and
isExecutable().
Member Function Documentation
QFileInfo::QFileInfo ()
Constructs a new empty QFileInfo.
QFileInfo::QFileInfo ( const QString & file )
Constructs a new QFileInfo that gives information about the given
file. The file can also include an absolute or relative path.
See also setFile(), isRelative(), QDir::setCurrent(), and QDir::isRelativePath().
QFileInfo::QFileInfo ( const QFile & file )
Constructs a new QFileInfo that gives information about file file.
If the file has a relative path, the QFileInfo will also have a
relative path.
See also isRelative().
QFileInfo::QFileInfo ( const QDir & d, const QString & fileName )
Constructs a new QFileInfo that gives information about the file
called fileName in the directory d.
If d has a relative path, the QFileInfo will also have a
relative path.
See also isRelative().
QFileInfo::QFileInfo ( const QFileInfo & fi )
Constructs a new QFileInfo that is a copy of fi.
QFileInfo::~QFileInfo ()
Destroys the QFileInfo and frees its resources.
QString QFileInfo::absFilePath () const
Returns the absolute path including the file name.
The absolute path name consists of the full path and the file
name. On Unix this will always begin with the root, '/',
directory. On Windows this will always begin 'D:/' where D is a
drive letter, except for network shares that are not mapped to a
drive letter, in which case the path will begin '//sharename/'.
This function returns the same as filePath(), unless isRelative()
is TRUE.
If the QFileInfo is empty it returns QDir::currentDirPath().
This function can be time consuming under Unix (in the order of
milliseconds).
See also isRelative() and filePath().
Examples: biff/biff.cpp and fileiconview/qfileiconview.cpp.
QString QFileInfo::baseName ( bool complete = FALSE ) const
Returns the base name of the file.
If complete is FALSE (the default) the base name consists of
all characters in the file name up to (but not including) the first '.' character.
If complete is TRUE the base name consists of all characters in
the file up to (but not including) the last '.' character.
The path is not included in either case.
Example:
QFileInfo fi( "/tmp/archive.tar.gz" );
QString base = fi.baseName(); // base = "archive"
base = fi.baseName( TRUE ); // base = "archive.tar"
See also fileName() and extension().
bool QFileInfo::caching () const
Returns TRUE if caching is enabled; otherwise returns FALSE.
See also setCaching() and refresh().
bool QFileInfo::convertToAbs ()
Converts the file's path to an absolute path.
If it is already absolute, nothing is done.
See also filePath() and isRelative().
QDateTime QFileInfo::created () const
Returns the date and time when the file was created.
On platforms where this information is not available, returns the
same as lastModified().
See also lastModified() and lastRead().
QDir QFileInfo::dir ( bool absPath = FALSE ) const
Returns the file's path as a QDir object.
If the QFileInfo is relative and absPath is FALSE, the QDir
will be relative; otherwise it will be absolute.
See also dirPath(), filePath(), fileName(), and isRelative().
Example: fileiconview/qfileiconview.cpp.
QString QFileInfo::dirPath ( bool absPath = FALSE ) const
Returns the file's path.
If absPath is TRUE an absolute path is returned.
See also dir(), filePath(), fileName(), and isRelative().
Example: fileiconview/qfileiconview.cpp.
bool QFileInfo::exists () const
Returns TRUE if the file exists; otherwise returns FALSE.
Examples: biff/biff.cpp, distributor/distributor.ui.h, and i18n/main.cpp.
QString QFileInfo::extension ( bool complete = TRUE ) const
Returns the file's extension name.
If complete is TRUE (the default), extension() returns the
string of all characters in the file name after (but not
including) the first '.' character.
If complete is FALSE, extension() returns the string of all
characters in the file name after (but not including) the last '.'
character.
Example:
QFileInfo fi( "/tmp/archive.tar.gz" );
QString ext = fi.extension(); // ext = "tar.gz"
ext = fi.extension( FALSE ); // ext = "gz"
See also fileName() and baseName().
Example: qdir/qdir.cpp.
QString QFileInfo::fileName () const
Returns the name of the file, excluding the path.
Example:
QFileInfo fi( "/tmp/archive.tar.gz" );
QString name = fi.fileName(); // name = "archive.tar.gz"
See also isRelative(), filePath(), baseName(), and extension().
Examples: dirview/dirview.cpp, fileiconview/qfileiconview.cpp, and network/ftpclient/ftpmainwindow.ui.h.
QString QFileInfo::filePath () const
Returns the file name, including the path (which may be absolute
or relative).
See also isRelative() and absFilePath().
Examples: dirview/main.cpp and fileiconview/qfileiconview.cpp.
QString QFileInfo::group () const
Returns the group of the file. On Windows, on systems where files
do not have groups, or if an error occurs, QString::null is
returned.
This function can be time consuming under Unix (in the order of
milliseconds).
See also groupId(), owner(), and ownerId().
uint QFileInfo::groupId () const
Returns the id of the group the file belongs to.
On Windows and on systems where files do not have groups this
function always returns (uint) -2.
See also group(), owner(), and ownerId().
bool QFileInfo::isDir () const
Returns TRUE if this object points to a directory or to a symbolic
link to a directory; otherwise returns FALSE.
See also isFile() and isSymLink().
Examples: dirview/dirview.cpp and fileiconview/qfileiconview.cpp.
bool QFileInfo::isExecutable () const
Returns TRUE if the file is executable; otherwise returns FALSE.
See also isReadable(), isWritable(), and permission().
bool QFileInfo::isFile () const
Returns TRUE if this object points to a file. Returns FALSE if the
object points to something which isn't a file, e.g. a directory or
a symlink.
See also isDir() and isSymLink().
Examples: dirview/dirview.cpp, distributor/distributor.ui.h, fileiconview/qfileiconview.cpp, and qdir/qdir.cpp.
bool QFileInfo::isHidden () const
Returns TRUE if the file is hidden; otherwise returns FALSE.
On Unix-like operating systems, including Mac OS X, a file is
hidden if its name begins with ".". On Windows a file is hidden if
its hidden attribute is set.
bool QFileInfo::isReadable () const
Returns TRUE if the user can write to the file; otherwise returns FALSE.
See also isWritable(), isExecutable(), and permission().
Example: distributor/distributor.ui.h.
bool QFileInfo::isRelative () const
Returns TRUE if the file path name is relative. Returns FALSE if
the path is absolute (e.g. under Unix a path is absolute if it
begins with a "/").
bool QFileInfo::isSymLink () const
Returns TRUE if this object points to a symbolic link (or to a
shortcut on Windows); otherwise returns FALSE.
See also isFile(), isDir(), and readLink().
Examples: dirview/dirview.cpp, distributor/distributor.ui.h, and fileiconview/qfileiconview.cpp.
bool QFileInfo::isWritable () const
Returns TRUE if the file is writable; otherwise returns FALSE.
See also isReadable(), isExecutable(), and permission().
Example: distributor/distributor.ui.h.
QDateTime QFileInfo::lastModified () const
Returns the date and time when the file was last modified.
See also created() and lastRead().
Example: biff/biff.cpp.
QDateTime QFileInfo::lastRead () const
Returns the date and time when the file was last read (accessed).
On platforms where this information is not available, returns the
same as lastModified().
See also created() and lastModified().
Example: biff/biff.cpp.
QFileInfo & QFileInfo::operator= ( const QFileInfo & fi )
Makes a copy of fi and assigns it to this QFileInfo.
QString QFileInfo::owner () const
Returns the owner of the file. On systems where files
do not have owners, or if an error occurs, QString::null is
returned.
This function can be time consuming under Unix (in the order of
milliseconds).
See also ownerId(), group(), and groupId().
uint QFileInfo::ownerId () const
Returns the id of the owner of the file.
On Windows and on systems where files do not have owners this
function returns ((uint) -2).
See also owner(), group(), and groupId().
bool QFileInfo::permission ( int permissionSpec ) const
Tests for file permissions. The permissionSpec argument can be
several flags of type PermissionSpec OR-ed together to check
for permission combinations.
On systems where files do not have permissions this function
always returns TRUE.
Example:
QFileInfo fi( "/tmp/archive.tar.gz" );
if ( fi.permission( QFileInfo::WriteUser | QFileInfo::ReadGroup ) )
qWarning( "I can change the file; my group can read the file" );
if ( fi.permission( QFileInfo::WriteGroup | QFileInfo::WriteOther ) )
qWarning( "The group or others can change the file" );
See also isReadable(), isWritable(), and isExecutable().
QString QFileInfo::readLink () const
Returns the name a symlink (or shortcut on Windows) points to, or
a QString::null if the object isn't a symbolic link.
This name may not represent an existing file; it is only a string.
QFileInfo::exists() returns TRUE if the symlink points to an
existing file.
See also exists(), isSymLink(), isDir(), and isFile().
void QFileInfo::refresh () const
Refreshes the information about the file, i.e. reads in information
from the file system the next time a cached property is fetched.
See also setCaching().
void QFileInfo::setCaching ( bool enable )
If enable is TRUE, enables caching of file information. If enable is FALSE caching is disabled.
When caching is enabled, QFileInfo reads the file information from
the file system the first time it's needed, but generally not
later.
Caching is enabled by default.
See also refresh() and caching().
void QFileInfo::setFile ( const QString & file )
Sets the file that the QFileInfo provides information about to file.
The file can also include an absolute or relative file path.
Absolute paths begin with the directory separator (e.g. "/" under
Unix) or a drive specification (under Windows). Relative file
names begin with a directory name or a file name and specify a
path relative to the current directory.
Example:
QString absolute = "/local/bin";
QString relative = "local/bin";
QFileInfo absFile( absolute );
QFileInfo relFile( relative );
QDir::setCurrent( QDir::rootDirPath() );
// absFile and relFile now point to the same file
QDir::setCurrent( "/tmp" );
// absFile now points to "/local/bin",
// while relFile points to "/tmp/local/bin"
See also isRelative(), QDir::setCurrent(), and QDir::isRelativePath().
Example: biff/biff.cpp.
void QFileInfo::setFile ( const QFile & file )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Sets the file that the QFileInfo provides information about to file.
If file includes a relative path, the QFileInfo will also have
a relative path.
See also isRelative().
void QFileInfo::setFile ( const QDir & d, const QString & fileName )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Sets the file that the QFileInfo provides information about to fileName in directory d.
If fileName includes a relative path, the QFileInfo will also
have a relative path.
See also isRelative().
uint QFileInfo::size () const
Returns the file size in bytes, or 0 if the file does not exist or
if the size is 0 or if the size cannot be fetched.
Example: qdir/qdir.cpp.
This file is part of the Qt toolkit.
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Trolltech. All Rights Reserved.
