FileUtils.jsm 编辑

The FileUtils.jsm JavaScript code module offers utility routines dealing with files. To use it, you first need to import the code module into your JavaScript scope:

Components.utils.import("resource://gre/modules/FileUtils.jsm");

The File constructor

If you have a path to a file (or directory) you want to obtain an nsIFile for, you can do so using the File constructor, like this:

var f = new FileUtils.File(mypath);

Method overview

Constants

Methods

getFile()

Gets a file at the specified hierarchy under a nsIDirectoryService key.

nsIFile getFile(
  string key,
  array pathArray,
  bool followLinks
);

Parameters

key

The nsIDirectoryService key to start from (see Getting special files for more info)

pathArray

An array of path components to locate beneath the directory specified by key. The last item in this array must be the leaf name of a file.

followLinks Optional

True if links should be followed, false otherwise.

Return value

Returns a nsIFile object for the file specified. The file is NOT created if it does not exist, however all required directories along the way are.

getDir()

Gets a directory at the specified hierarchy under a nsIDirectoryService key.

nsIFile getDir(
  string key,
  array pathArray,
  bool shouldCreate,
  bool followLInks
);

Parameters

key

The nsIDirectoryService key to start from (see Getting special files for more info)

pathArray

An array of path components to locate beneath the directory specified by key.

shouldCreate Optional

True if the directory hierarchy specified in pathArray should be created if it does not exist, false otherwise.

followLinks Optional

True if links should be followed, false otherwise location specified.

Return value

Returns a nsIFile object for the location specified. If the directory requested does not exist, it is created, along with any parent directories that need to be created.

Note: If you want to use the full path to get to the directory you cannot use getDir. Instead use the file constructor, so simply:

var dir = new FileUtils.File('C:\\blah\\blah');
if (dir.exists()) {
  //yes directory exists
}

openFileOutputStream()

Opens a file output stream for writing.

The stream is opened with the DEFER_OPEN nsIFileOutputStream.Behavior flag constant this means the file is not actually opened until the first time it's accessed.

nsIFileOutputStream openFileOutputStream(
  nsIFile file,
  int modeFlags
);

Parameters

file

The file to write to.

modeFlags Optional

File open flags (see constants above)

Return value

Returns nsIFileOutputStream (the non-safe variant) to write to.

openAtomicFileOutputStream()

Opens an atomic file output stream for writing.

Note: 'safe' and 'atomic' file output streams will never append; they will always overwrite an existing file.

Starting in Gecko 38.0, passing MODE_APPEND without MODE_TRUNCATE will throw an exception.

nsIFileOutputStream openAtomicFileOutputStream(
  nsIFile file,
  int modeFlags
);

Parameters

file

The file to write to.

modeFlags Optional

File open flags (see constants above)

Return value

Returns nsIFileOutputStream (the safe variant) to write to.

closeAtomicFileOutputStream()

Closes an atomic file output stream.

void closeAtomicFileOutputStream(
  nsIFileOutputStream stream
);

Parameters

stream

The stream to close.

openSafeFileOutputStream()

Opens a safe file output stream for writing.

Note: 'safe' and 'atomic' file output streams will never append; they will always overwrite an existing file.

Starting in Gecko 38.0, passing MODE_APPEND without MODE_TRUNCATE will throw an exception.

nsIFileOutputStream openSafeFileOutputStream(
  nsIFile file,
  int modeFlags
);

Parameters

file

The file to write to.

modeFlags Optional

File open flags (see constants above)

Return value

Returns nsIFileOutputStream (the safe variant) to write to.

Remarks

Note: Starting in Gecko 6 the stream is opened with the DEFER_OPEN nsIFileOutputStream Behavior flag constant; this means the file is not actually opened until the first time it's accessed.

closeSafeFileOutputStream()

Closes a safe file output stream.

void closeSafeFileOutputStream(
  nsIFileOutputStream stream
);

Parameters

stream

The stream to close.

See also

• nsIFileOutputStream
• Code Snippets and Examples