About Storing Files: Where and How?

Source directory, current directory, home directory, temporary directory …

About Locations For Storing Files, 1

About directories (synonym: folders)
- Can be nested (directory/folder in a directory/folder …)
- Root directory has the symbol "/" (Unix) or "\" (Windows)
  - Windows has the notion of a drive, an alphabetic letter followed by a colon, e.g. "C:"
    - A drive may be prepended to the directory, e.g. to the root directory: "C:\"
- A PATH is the sequence of directories (folders) to traverse to arrive at the storage location of a file
  - Each directory (folder) gets separated with the letter "/" (Unix) or "\" (Windows)
  - Windows examples for absolute (starts with the root directory/folder) and relative paths
    
    C:\Users\JohnDoe\Documents\someFile1.png (absolute path)
    
    Documents\someFile2.png (relative path: relative to current directory/folder)
  - Unix examples for absolute and relative paths
    
    /Users/MaryDoe/Documents/someFile1.png (absolute path)
    
    Documents/someFile2.png (relative path: relative to current directory/folder)

Source Directory

The directory where the Rexx program is stored
- Can be retrieved from Rexx using the PARSE SOURCE keyword statement
```
PARSE SOURCE opsys invocationType pathToRexxProgram
```
  - opsys refers to the operating system, e.g. "Windows", "Darwin" (Apple), "Linux", …
  - invocationType is one of "COMMAND", "FUNCTION", "SUBROUTINE", "METHOD", "REQUIRES"
  - pathToRexxProgram is the fully qualified path to the Rexx program, e.g.
    
    C:\Users\JohnDoe\programs\someProgram.rex (absolute path, Windows)
    
    /Users/MaryDoe/programs/someProgram.rex (absolute path, Unix)
- FILESPEC()-BIF (built-in-function) allows to retrieve different parts of a path
  
  e.g. FILESPEC('location', pathToRexxProgram) yields for the above two examples:
  
  C:\Users\JohnDoe\programs\ (Windows example location)
  
  /Users/MaryDoe/programs/ (Unix example location)

Current Directory

The directory (folder) where the Rexx program executes
- Used for looking up additional programs and files without a path
- Can be changed arbitrarily while the program executes
directory(optionalNewDir)-BIF (built-in-function)
- Returns the full path to the current directory
- If argument optionalNewDir supplied, changes the current directory to it
Example:

say directory()        -- returns path to current directory
oldDir=directory("..") -- changes to parent directory/folder ("."=current, ".."=parent directory/folder)
say directory()        -- returns path to current directory

Output Windows, assuming current directory is
C:\Users\MaryDoe\temp:

Output Unix, assuming current directory is
/Users/JohnDoe/temp:

C:\Users\MaryDoe\temp
C:\Users\MaryDoe

/Users/JohnDoe/temp
/Users/JohnDoe

Home Directory

The directory (folder) where all files and directories/folders of a user reside
- User usually has all permissions for all directories/folders and files therein
Operating system defines an environment variable that contains the path
- Environment variable (Windows): "USERPROFILE"
- Environment variable (UNIX): "HOME"

Use the value()-BIF (built-in-function) to retrieve the environment variable's value, e.g.

Example Windows:

homeDir=value('USERPROFILE', ,'ENVIRONMENT') -- maybe: "C:\Users\JohnDoe"

Example Unix:

homeDir=value('HOME', ,'ENVIRONMENT')        -- maybe: "/Users/MaryDoe"

Temporary Directory

Every operating system defines a directory for temporary files
- Rights for everyone to read and write files
  - May be emptied by the operating system, e.g. during boot process
  - Beware of storing sensitive data there!
Temporary directories on different operating systems
- Windows: defined with the environment variable "TMP" or "TEMP"
```
tempDir=value('TEMP',,'ENVIRONMENT')   -- maybe "C:\Users\JohnDoe\AppData\Local\Temp"
```
- MacOS: defined with the environment variable "TMPDIR"
```
tempDir=value('TMPDIR',,'ENVIRONMENT') -- maybe "/var/folders/x9/gyg5hmn/T/"
```
- Unix: usually the directory "/tmp"

Using Java to Fetch these Directories

Java's java.util.System class manages the properties for the system
- The following properties are set according to the user's operating system

Directory	Name of System Property
Current directory	"`user.dir`"
Home directory	"`user.home`"
Temporary directory	"`java.io.tmpdir`"

say "User name            :" .java.lang.System~getProperty("user.name")
say "User's home directory:" .java.lang.System~getProperty("user.home")
say "Current directory    :" .java.lang.System~getProperty("user.dir")
say "Temp directory       :" .java.lang.System~getProperty("java.io.tmpdir")

::requires BSF.CLS -- get ooRexx-Java bridge

Possible output (Windows) assuming current directory is C:\Program Files\ooRexx:

User name            : JohnDoe
User's home directory: C:\Users\JohnDoe
Current directory    : C:\Program Files\ooRexx
Temp directory       : C:\Users\JohnDoe\AppData\Local\Temp\

Contact

WU

Prof. Mag. Dr. Rony G. Flatscher

Welthandelsplatz 1

1020 Wien/Vienna

Austria/Europe

www: www.wu.ac.at