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.
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|
|"/PACKAGE"||Database folder (with or without 4dbase extension)|
|"/RESOURCES"||Current database resources folder|
|"/SOURCES"||Current project resources folder|
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
Folder commands, for example:
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 "\".
$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
\ 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 ":"
$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
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
.folder() folder functions
Functions of folder objects such as
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)