cheat sheets.

=========================================================================
--> Kernel#test(command, path [, path2])
=========================================================================

  * used to test the characteristics of the disk path represented
    in the string argument 'path'
  * also provides a few comparison tests between two path strings
  * command is an integer, usually specified with a character
    literal (i.e. ?e)
  * characters commands have loose mnemonic mappings,
    for example: ?f => path is a file?

=========================================================================
--> test Commands Arranged by Subject
-------------------------------------------------------------------------
* Single Path Tests
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Path Existence:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?e    | path exists                                       |
    +---------+---------------------------------------------------+

Path Type:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?f    | regular file?                                     |
    |   ?d    | directory?                                        |
    |   ?l    | symbolic link?                                    |
    |   ?p    | fifo?                                             |
    |   ?S    | socket?                                           |
    |   ?b    | block device?                                     |
    |   ?c    | character device?                                 |
    +---------+---------------------------------------------------+

File Size:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?z    | path size zero?                                   |
    |   ?s    | path size if size >= 0                            |
    +---------+---------------------------------------------------+

Path Timestamps:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?A    | last access time (file read)                      |
    |   ?C    | last change time (file metadata modified)         |
    |   ?M    | last modification time (file content modified)    |
    +---------+---------------------------------------------------+

Path Ownership:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?G    | group ownership equal to the caller's group?      |
    |   ?o    | owned by caller's *effective* user id?            |
    |   ?O    | owned by caller's *real* user id?                 |
    +---------+---------------------------------------------------+

Path Permissions:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?r    | readable by caller's effective user/group id?     |
    |   ?R    | readable by caller's real user/group id?          |
    |   ?w    | writable by caller's effective user/group id?     |
    |   ?W    | writable by caller's real user/group id?          |
    |   ?x    | executable by caller's effective user/group id?   |
    |   ?X    | executable by caller's real user/group id?        |
    +---------+---------------------------------------------------+

Misc. Path Attributes:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?k    | path has the sticky bit set?                      |
    |   ?u    | path has the setuid bit set?                      |
    |   ?g    | path has the setgid bit set?                      |
    +---------+---------------------------------------------------+

-------------------------------------------------------------------------
* Path Comparison Tests
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
File Equality:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?-    | the two paths are identical                       |
    +---------+---------------------------------------------------+

Modification Times:

    +---------+---------------------------------------------------+
    | Command | Description                                       |
    +---------+---------------------------------------------------+
    |   ?=    | paths last modified at the same time              |
    |   ?<    | path2 modified more recently than path1           |
    |   ?>    | path1 modified more recently than path2           |
    +---------+---------------------------------------------------+