QFileInfo Class

  #ifdef Q_OS_UNIX

  QFileInfo info1("/home/bob/bin/untabify");
  info1.isSymLink();          // returns true
  info1.absoluteFilePath();   // returns "/home/bob/bin/untabify"
  info1.size();               // returns 56201
  info1.symLinkTarget();      // returns "/opt/pretty++/bin/untabify"

  QFileInfo info2(info1.symLinkTarget());
  info2.isSymLink();          // returns false
  info2.absoluteFilePath();   // returns "/opt/pretty++/bin/untabify"
  info2.size();               // returns 56201

  #endif

  #ifdef Q_OS_WIN

  QFileInfo info1("C:\\Documents and Settings\\Bob\\untabify.lnk");
  info1.isSymLink();          // returns true
  info1.absoluteFilePath();   // returns "C:/Documents and Settings/Bob/untabify.lnk"
  info1.size();               // returns 743
  info1.symLinkTarget();      // returns "C:/Pretty++/untabify"

  QFileInfo info2(info1.symLinkTarget());
  info2.isSymLink();          // returns false
  info2.absoluteFilePath();   // returns "C:/Pretty++/untabify"
  info2.size();               // returns 63942

  #endif

  extern Q_CORE_EXPORT int qt_ntfs_permission_lookup;

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

成员函数

QFileInfo::QFileInfo()

Constructs an empty QFileInfo object.

Note that an empty QFileInfo object contain no file reference.

参见 setFile().

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.

参见 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.

参见 isRelative().

QFileInfo::QFileInfo(const QDir &dir, const QString &file)

Constructs a new QFileInfo that gives information about the given file in the directory dir.

If dir has a relative path, the QFileInfo will also have a relative path.

If file is an absolute path, then the directory specified by dir will be disregarded.

参见 isRelative().

QFileInfo::QFileInfo(const QFileInfo &fileinfo)

Constructs a new QFileInfo that is a copy of the given fileinfo.

QFileInfo::~QFileInfo()

Destroys the QFileInfo and frees its resources.

QDir QFileInfo::absoluteDir() const

Returns the file's absolute path as a QDir object.

参见 dir(), filePath(), fileName(), and isRelative().

QString QFileInfo::absoluteFilePath() const

Returns an 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/'. QFileInfo will uppercase drive letters. Note that QDir does not do this. The code snippet below shows this.

      QFileInfo fi("c:/temp/foo"); => fi.absoluteFilePath() => "C:/temp/foo"

This function returns the same as filePath(), unless isRelative() is true. In contrast to canonicalFilePath(), symbolic links or redundant "." or ".." elements are not necessarily removed.

Warning: If filePath() is empty the behavior of this function is undefined.

参见 filePath(), canonicalFilePath(), and isRelative().

QString QFileInfo::absolutePath() const

Returns a file's path absolute path. This doesn't include the file name.

On Unix the absolute path 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/'.

In contrast to canonicalPath() symbolic links or redundant "." or ".." elements are not necessarily removed.

Warning: If filePath() is empty the behavior of this function is undefined.

参见 absoluteFilePath(), path(), canonicalPath(), fileName(), and isRelative().

QString QFileInfo::baseName() const

Returns the base name of the file without the path.

The base name consists of all characters in the file up to (but not including) the first '.' character.

Example:

  QFileInfo fi("/tmp/archive.tar.gz");
  QString base = fi.baseName();  // base = "archive"

The base name of a file is computed equally on all platforms, independent of file naming conventions (e.g., ".bashrc" on Unix has an empty base name, and the suffix is "bashrc").

参见 fileName(), suffix(), completeSuffix(), and completeBaseName().

QString QFileInfo::bundleName() const

Returns the name of the bundle.

On macOS and iOS this returns the proper localized name for a bundle if the path isBundle(). On all other platforms an empty QString is returned.

Example:

  QFileInfo fi("/Applications/Safari.app");
  QString bundle = fi.bundleName();                // name = "Safari"

This function was introduced in Qt 4.3.

参见 isBundle(), filePath(), baseName(), and suffix().

bool QFileInfo::caching() const

Returns true if caching is enabled; otherwise returns false.

参见 setCaching() and refresh().

QString QFileInfo::canonicalFilePath() const

Returns the canonical path including the file name, i.e. an absolute path without symbolic links or redundant "." or ".." elements.

If the file does not exist, canonicalFilePath() returns an empty string.

参见 filePath(), absoluteFilePath(), and dir().

QString QFileInfo::canonicalPath() const

Returns the file's path canonical path (excluding the file name), i.e. an absolute path without symbolic links or redundant "." or ".." elements.

If the file does not exist, canonicalPath() returns an empty string.

参见 path() and absolutePath().

QString QFileInfo::completeBaseName() const

Returns the complete base name of the file without the path.

The complete base name consists of all characters in the file up to (but not including) the last '.' character.

Example:

  QFileInfo fi("/tmp/archive.tar.gz");
  QString base = fi.completeBaseName();  // base = "archive.tar"

参见 fileName(), suffix(), completeSuffix(), and baseName().

QString QFileInfo::completeSuffix() const

Returns the complete suffix (extension) of the file.

The complete suffix consists of all characters in the file after (but not including) the first '.'.

Example:

  QFileInfo fi("/tmp/archive.tar.gz");
  QString ext = fi.completeSuffix();  // ext = "tar.gz"

参见 fileName(), suffix(), baseName(), and completeBaseName().

QDateTime QFileInfo::created() const

Returns the date and local time when the file was created.

On most Unix systems, this function returns the time of the last status change. A status change occurs when the file is created, but it also occurs whenever the user writes or sets inode information (for example, changing the file permissions).

If neither creation time nor "last status change" time are not available, returns the same as lastModified().

参见 lastModified() and lastRead().

QDir QFileInfo::dir() const

Returns the path of the object's parent directory as a QDir object.

Note: The QDir returned always corresponds to the object's parent directory, even if the QFileInfo represents a directory.

For each of the following, dir() returns a QDir for "~/examples/191697".

      QFileInfo fileInfo1("~/examples/191697/.");
      QFileInfo fileInfo2("~/examples/191697/..");
      QFileInfo fileInfo3("~/examples/191697/main.cpp");

For each of the following, dir() returns a QDir for ".".

      QFileInfo fileInfo4(".");
      QFileInfo fileInfo5("..");
      QFileInfo fileInfo6("main.cpp");

参见 absolutePath(), filePath(), fileName(), isRelative(), and absoluteDir().

bool QFileInfo::exists() const

Returns true if the file exists; otherwise returns false.

Note: If the file is a symlink that points to a non-existing file, false is returned.

[static] bool QFileInfo::exists(const QString &file)

Returns true if the file exists; otherwise returns false.

Note: If file is a symlink that points to a non-existing file, false is returned.

Note: Using this function is faster than using QFileInfo(file).exists() for file system access.

This function was introduced in Qt 5.2.

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"

Note that, if this QFileInfo object is given a path ending in a slash, the name of the file is considered empty.

参见 isRelative(), filePath(), baseName(), and suffix().

QString QFileInfo::filePath() const

Returns the file name, including the path (which may be absolute or relative).

参见 absoluteFilePath(), canonicalFilePath(), and isRelative().

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, an empty string is returned.

This function can be time consuming under Unix (in the order of milliseconds).

参见 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.

参见 group(), owner(), and ownerId().

bool QFileInfo::isAbsolute() const

Returns true if the file path name is absolute, otherwise returns false if the path is relative.

参见 isRelative().

bool QFileInfo::isBundle() const

Returns true if this object points to a bundle or to a symbolic link to a bundle on macOS and iOS; otherwise returns false.

This function was introduced in Qt 4.3.

参见 isDir(), isSymLink(), and isFile().

bool QFileInfo::isDir() const

Returns true if this object points to a directory or to a symbolic link to a directory; otherwise returns false.

参见 isFile(), isSymLink(), and isBundle().

bool QFileInfo::isExecutable() const

Returns true if the file is executable; otherwise returns false.

参见 isReadable(), isWritable(), and permission().

bool QFileInfo::isFile() const

Returns true if this object points to a file or to a symbolic link to a file. Returns false if the object points to something which isn't a file, such as a directory.

参见 isDir(), isSymLink(), and isBundle().

bool QFileInfo::isHidden() const

Returns true if this is a `hidden' file; otherwise returns false.

Note: This function returns true for the special entries "." and ".." on Unix, even though QDir::entryList threats them as shown.

bool QFileInfo::isNativePath() const

Returns true if the file path can be used directly with native APIs. Returns false if the file is otherwise supported by a virtual file system inside Qt, such as the Qt Resource System.

Note: Native paths may still require conversion of path separators and character encoding, depending on platform and input requirements of the native API.

This function was introduced in Qt 5.0.

参见 QDir::toNativeSeparators(), QFile::encodeName(), filePath(), absoluteFilePath(), and canonicalFilePath().

bool QFileInfo::isReadable() const

Returns true if the user can read the file; otherwise returns false.

Note: If the NTFS permissions check has not been enabled, the result on Windows will merely reflect whether the file exists.

参见 isWritable(), isExecutable(), and permission().

bool QFileInfo::isRelative() const

Returns true if the file path name is relative, otherwise returns false if the path is absolute (e.g. under Unix a path is absolute if it begins with a "/").

参见 isAbsolute().

bool QFileInfo::isRoot() const

Returns true if the object points to a directory or to a symbolic link to a directory, and that directory is the root directory; otherwise returns false.

bool QFileInfo::isSymLink() const

Returns true if this object points to a symbolic link (or to a shortcut on Windows); otherwise returns false.

On Unix (including macOS and iOS), opening a symlink effectively opens the link's target. On Windows, it opens the .lnk file itself.

Example:

  QFileInfo info(fileName);
  if (info.isSymLink())
      fileName = info.symLinkTarget();

Note: If the symlink points to a non existing file, exists() returns false.

参见 isFile(), isDir(), and symLinkTarget().

bool QFileInfo::isWritable() const

Returns true if the user can write to the file; otherwise returns false.

Note: If the NTFS permissions check has not been enabled, the result on Windows will merely reflect whether the file is marked as Read Only.

参见 isReadable(), isExecutable(), and permission().

QDateTime QFileInfo::lastModified() const

Returns the date and local time when the file was last modified.

参见 created() and lastRead().

QDateTime QFileInfo::lastRead() const

Returns the date and local time when the file was last read (accessed).

On platforms where this information is not available, returns the same as lastModified().

参见 created() and lastModified().

bool QFileInfo::makeAbsolute()

Converts the file's path to an absolute path if it is not already in that form. Returns true to indicate that the path was converted; otherwise returns false to indicate that the path was already absolute.

参见 filePath() and isRelative().

QString QFileInfo::owner() const

Returns the owner of the file. On systems where files do not have owners, or if an error occurs, an empty string is returned.

This function can be time consuming under Unix (in the order of milliseconds). On Windows, it will return an empty string unless the NTFS permissions check has been enabled.

参见 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).

参见 owner(), group(), and groupId().

QString QFileInfo::path() const

Returns the file's path. This doesn't include the file name.

Note that, if this QFileInfo object is given a path ending in a slash, the name of the file is considered empty and this function will return the entire path.

参见 filePath(), absolutePath(), canonicalPath(), dir(), fileName(), and isRelative().

bool QFileInfo::permission(QFile::Permissions permissions) const

Tests for file permissions. The permissions argument can be several flags of type QFile::Permissions OR-ed together to check for permission combinations.

On systems where files do not have permissions this function always returns true.

Note: The result might be inaccurate on Windows if the NTFS permissions check has not been enabled.

Example:

  QFileInfo fi("/tmp/archive.tar.gz");
  if (fi.permission(QFile::WriteUser | QFile::ReadGroup))
      qWarning("I can change the file; my group can read the file");
  if (fi.permission(QFile::WriteGroup | QFile::WriteOther))
      qWarning("The group or others can change the file");

参见 isReadable(), isWritable(), and isExecutable().

QFile::Permissions QFileInfo::permissions() const

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

Note: The result might be inaccurate on Windows if the NTFS permissions check has not been enabled.

void QFileInfo::refresh()

Refreshes the information about the file, i.e. reads in information from the file system the next time a cached property is fetched.

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.

参见 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::rootPath());
  // 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"

参见 isFile(), isRelative(), QDir::setCurrent(), and QDir::isRelativePath().

void QFileInfo::setFile(const QFile &file)

This is an overloaded 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.

参见 isRelative().

void QFileInfo::setFile(const QDir &dir, const QString &file)

This is an overloaded function.

Sets the file that the QFileInfo provides information about to file in directory dir.

If file includes a relative path, the QFileInfo will also have a relative path.

参见 isRelative().

qint64 QFileInfo::size() const

Returns the file size in bytes. If the file does not exist or cannot be fetched, 0 is returned.

参见 exists().

QString QFileInfo::suffix() const

Returns the suffix (extension) of the file.

The suffix consists of all characters in the file after (but not including) the last '.'.

Example:

  QFileInfo fi("/tmp/archive.tar.gz");
  QString ext = fi.suffix();  // ext = "gz"

The suffix of a file is computed equally on all platforms, independent of file naming conventions (e.g., ".bashrc" on Unix has an empty base name, and the suffix is "bashrc").

参见 fileName(), completeSuffix(), baseName(), and completeBaseName().

void QFileInfo::swap(QFileInfo &other)

Swaps this file info with other. This function is very fast and never fails.

This function was introduced in Qt 5.0.

QString QFileInfo::symLinkTarget() const

Returns the absolute path to 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. QFileInfo::exists() returns true if the symlink points to an existing file.

This function was introduced in Qt 4.2.

参见 exists(), isSymLink(), isDir(), and isFile().

bool QFileInfo::operator!=(const QFileInfo &fileinfo) const

Returns true if this QFileInfo object refers to a different file than the one specified by fileinfo; otherwise returns false.

参见 operator==().

QFileInfo &QFileInfo::operator=(const QFileInfo &fileinfo)

Makes a copy of the given fileinfo and assigns it to this QFileInfo.

QFileInfo &QFileInfo::operator=(QFileInfo &&other)

Move-assigns other to this QFileInfo instance.

This function was introduced in Qt 5.2.

bool QFileInfo::operator==(const QFileInfo &fileinfo) const

Returns true if this QFileInfo object refers to a file in the same location as fileinfo; otherwise returns false.

Note that the result of comparing two empty QFileInfo objects, containing no file references (file paths that do not exist or are empty), is undefined.

Warning: This will not compare two different symbolic links pointing to the same file.

Warning: Long and short file names that refer to the same file on Windows are treated as if they referred to different files.

参见 operator!=().