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From: Martin Gregorie on 14 Jul 2008 14:58
On Mon, 14 Jul 2008 11:13:35 +0000, Stefan Ram wrote:

> I also would like to know what this program prints on other
> systems (especially on a Linux System, but also different
> variants of Windows), but feel free to remove parts of the
> output to protect privacy or security.
>
Here you go:

$ java Main
os.name =
Linux

os.version =
2.6.25.9-40.fc8 # I'm running RedHat Fedora 8

java.home =
/home/java/jdk1.6.0_05/jre # with Sun JDK 1.6.05

user.home = # My login directory when I ran it
/home/kiwi

user.dir = # My current working directory at the time
/home/kiwi/compiler_tests/environ

java.io.tmpdir = # default for FC8
/tmp

fileSystemView.getDefaultDirectory() = # $HOME (see below)
/home/kiwi
/home/kiwi

fileSystemView.getHomeDirectory() = # $HOME (set when user logged in)
/home/kiwi
/home/kiwi

getCodeSource().getLocation() = # As for user.dir
/home/kiwi/compiler_tests/environ
/home/kiwi/compiler_tests/environ

Linux, like all Unices, has a number of additional defaults at both user
and system level that we'd normally expect to be set for the particular
host:

- $PATH is where the OS looks for executables. It is typically something
like:

/bin:/usr/bin:/usr/local/bin

which are (respectively) where os essentials, programs installed as part
of the distro, and locally installed and/or written executables live.
'.' (the current dir) isn't on the search path by default but is
reasonably commonly added, together directories containing major
3rd party packages such as Oracle.

These defaults can be customised at both user and system level. The OS
has facilities to make this easier and to let customisations survive
OS reinstalls and upgrades.

If the user is privileged, e.g. root, they will also have
/sbin, /usr/sbin and possibly /usr/local/sbin in $PATH

This shouldn't normally concern a Java application but its mentioned for
completeness.

- unlike Windows, you'd normally expect to find config files for
standard packages in /etc and for locally installed/written packages
in /usr/local/etc, possibly with user specific configurations in hidden
files in $HOME. A 'hidden' file's name starts with '.' and isn't shown
in a directory listing or a wild carded list unless explicitly asked
for. This gives a little protection against accidental deletion etc.

This does have implications for Java apps. You might reasonably expect a
configurable Java app to search (in order) the current directory,
$HOME, /usr/local/etc and /etc for its config file/properties file and
use the first it found. Alternatively, if progressively localised
customisations are are to be applied to a default config, it would be
reasonable to do the search in the opposite order, and apply all files
in the order they are found to build up a final configuration for the
current user.

I think the way /etc and its siblings is used is the major difference from
Windows and its not really portable to another OS, except by coding the
search into the app and using the os.name property to determine which
search strategy should be used.

One other point: many *nix utilities use a config file format that's
compatible with a properties file. Comments start with #, individual
parameters are written as "name = value".

HTH


--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot


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