file

The file module provides access to the local filesystem.

Paths

Path specifications in this API are platform-specific. This means that on Windows paths are specified using the backslash path separator (\), and on Unix-like systems like Linux and OS X paths are specified using the forward slash path separator (/).

If your add-on uses literal Windows-style path specifications with this API, your add-on likely won't work when users run it on Unix-like systems. Likewise, if your add-on uses literal Unix-style path specifications, it won't work for users on Windows.

To ensure your add-on works for everyone, generate paths using the join function. Unfortunately this API does not currently provide a way to obtain an absolute base path which you could then use with join. For now, you need to require("chrome") and use the XPCOM directory service as described at MDN.

Note that if you do decide to hardcode Windows-style paths, be sure to escape backslashes in strings. For example, to specify the file at C:\Users\Myk, you need to use the string "C:\\Users\\Myk", not "C:\Users\Myk". You can read more about escaping characters in strings at MDN.

API Reference

Functions

basename(path)

Returns the last component of the given path. For example, basename("/foo/bar/baz") returns "baz". If the path has no components, the empty string is returned.

path : string

The path of a file.

Returns: string

The last component of the given path.

dirname(path)

Returns the path of the directory containing the given file. If the file is at the top of the volume, the empty string is returned.

path : string

The path of a file.

Returns: string

The path of the directory containing the file.

exists(path)

Returns true if a file exists at the given path and false otherwise.

path : string

The path of a file.

Returns: boolean

True if the file exists and false otherwise.

join(...)

Takes a variable number of strings, joins them on the file system's path separator, and returns the result.

... : strings

A variable number of strings to join. The first string must be an absolute path.

Returns: string

A single string formed by joining the strings on the file system's path separator.

list(path)

Returns an array of file names in the given directory.

path : string

The path of the directory.

Returns: array

An array of file names. Each is a basename, not a full path.

mkpath(path)

Makes a new directory named by the given path. Any subdirectories that do not exist are also created. mkpath can be called multiple times on the same path.

path : string

The path to create.

open(path, mode)

Returns a stream providing access to the contents of a file.

path : string

The path of the file to open.

[ mode : string ]

An optional string, each character of which describes a characteristic of the returned stream. If the string contains "r", the file is opened in read-only mode. "w" opens the file in write-only mode. "b" opens the file in binary mode. If "b" is not present, the file is opened in text mode, and its contents are assumed to be UTF-8. If mode is not given, "r" is assumed, and the file is opened in read-only text mode.

Returns: stream

If the file is opened in text read-only mode, a TextReader is returned, and if text write-only mode, a TextWriter is returned. See text-streams for information on these text stream objects. If the file is opened in binary read-only mode, a ByteReader is returned, and if binary write-only mode, a ByteWriter is returned. See byte-streams for more information on these byte stream objects. Opened files should always be closed after use by calling close on the returned stream.

read(path, mode)

Opens a file and returns a string containing its entire contents.

path : string

The path of the file to read.

[ mode : string ]

An optional string, each character of which describes a characteristic of the returned stream. If the string contains "b", the contents will be returned in binary mode. If "b" is not present or mode is not given, the file contents will be returned in text mode.

Returns: string

A string containing the file's entire contents.

remove(path)

Removes a file from the file system. To remove directories, use rmdir.

path : string

The path of the file to remove.

rmdir(path)

Removes a directory from the file system. If the directory is not empty, an exception is thrown.

path : string

The path of the directory to remove.