QFileInfo Class

Qt 3.0.5

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QFileInfo Class Reference

The QFileInfo class provides system-independent file information. More...

#include <qfileinfo.h>

List of all member functions.

Public Members

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 a drive specification (except on Unix). 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::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.

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 be an absolute or a relative file 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 named fileName in the directory d.

If the directory 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.

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 path name 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 directory path of the file.

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 directory path of the file.

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 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, the file path is not included.

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 and fileiconview/qfileiconview.cpp.

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, a null string 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, fileiconview/qfileiconview.cpp and qdir/qdir.cpp.

bool QFileInfo::isReadable () const

Returns TRUE if the file is readable; otherwise returns FALSE.

See also isWritable(), isExecutable() and permission().

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 and fileiconview/qfileiconview.cpp.

bool QFileInfo::isWritable () const

Returns TRUE if the file is writable; otherwise returns FALSE.

See also isReadable(), isExecutable() and permission().

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 Windows, on systems where files do not have owners, or if an error occurs, a null string 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 null QString 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 string given can be an absolute or a relative file path. Absolute paths begin with the directory separator (e.g. "/" under Unix) or a drive specification (not applicable to Unix). 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 the file has 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 the file has 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. Copyright © 1995-2002 Trolltech. All Rights Reserved.

Copyright © 2002 TrolltechTrademarks
Qt version 3.0.5

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