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Version: v20 BETA


File and Folder functions, properties, and commands allow you to handle files and folders as objects. This makes file and folder management powerful and flexible. For example, to create a new file in the current user's Documents folder, you can write:

$ok:=Folder(fk documents folder).file("Archives/John4D.prefs").create()

In addition, file and folder objects support fileSystems, which provide contextual path to main application folders.

Filesystem pathnames

4D accepts several filesystem pathnames that designate specific 4D folders with variable location on macOS and Windows. Filesystem pathnames are useful for two main reasons:

  • Independence: You can move your solution from one place to another regardless of the OS, without having to worry about paths,
  • Security: No code can access elements located above the file system root on the disk (sandboxing).

The following filesystem pathnames are supported:

"/DATA"Current data folder
"/LOGS"Logs folder
"/PACKAGE"Database folder (with or without 4dbase extension)
"/PROJECT"Project folder
"/RESOURCES"Current database resources folder
"/SOURCES"Current project resources folder

POSIX syntax

The POSIX syntax is supported on all platforms. POSIX syntax is recommended since it is the most flexible. It is used by default (returned by file.path and folder.path properties).

With this syntax:

  • folders are separated by "/"
  • absolute pathnames start with a "/"
  • to move up one folder in a relative path, use "../" in front of the pathname (for security, you cannot move up the filesystem).

In POSIX syntax, you will generally use filesystem pathnames with File and Folder commands, for example:

$pathFile:=File("/DATA/Archives/file 2.txt")

Platform-specific syntax

Platform-specific syntax depends on the operating system on which the command is executed. Note that when creating a file or folder object with this syntax, you must declare it using the fk platform path constant as parameter.


The following patterns are supported:

  • folder separators are "\"
  • the text contains ":" and "\" as the second and third character,
  • the text starts with "\".

Examples with Folder:

$ok:=Folder("C:\\Monday";fk platform path).create()
$ok:=Folder("\\\\svr-internal\\tempo";fk platform path).create()

Windows pathnames and escape sequences

The 4D language allows the use of escape sequences. Escape sequences begin with a backslash \, followed by a character. For example, \t is the escape sequence for the Tab character.

Since the \ character is also used as the separator in pathnames in Windows, you need to enter a double \\ in windows pathnames.


The following patterns are supported (HFS+ syntax):

  • folder separators are ":"
  • the path must not start with a ":"

Examples with Folder:

$ok:=Folder("macintosh hd:";fk platform path).create()
$ok:=Folder("Monday:Tuesday";fk platform path).create() //a volume must be called Monday

Absolute and relative pathnames

File and Folder constructors

File and Folder commands only accept absolute pathnames. Relative pathnames are not supported and will return errors. For example, the following code is not allowed:

$ko:=Folder("myFolder").create() //relative pathname with constructor

If you want to handle files or folders in various locations (project folder, system folders, etc.), you can use filesystems (see above). For example, you can write:

$okFolder:=Folder("/PACKAGE/myFolder").create() //folder created at the structure level
$okFile:=File("/DATA/Prefs/tempo.txt").create() //file created in the data folder

.file() and .folder() folder functions

Functions of folder objects such as folder.file() and folder.folder() expect relative POSIX pathnames. For example:

  //to reference a "Picture" folder within the user documents folder
$userImages:=Folder(fk documents folder).folder("Pictures")
//to create a folder on the desktop
$ok:=Folder(fk desktop folder).folder("myFolder").create()

Absolute pathnames are not supported and will return errors.


The flexibility of file and folder functions offers you various possibilities for handling files and folders, like in the following examples:

$f:=Folder(fk desktop folder).folder("archive/jan2019")




$f5:=File("c:\\archives\\local\\jan2019.txt";fk platform path)

$f6:=File(fk backup log file)