Directory handling

[Mark Evenson]

> On Jun 5, 2019, at 17:53, Marco Antoniotti <marco.antoniotti at unimib.it> wrote:
> 
> Dear all,
> 
> I have been looking at the ABCL manual and packages and I was not able (my fault!) to find functions like CURRENT-DIRECTORY and/or CHANGE-DIRECTORY (or CHDIR).
> 
> Could you tell me how to get to this functionality?

Unfortunately, the JVM doesn’t have a [standard interface to change the working directory][1] there is no direct method to setting the current working directory.  The JVM gets a copy of the system environment variables including the current working directory

[1]: https://stackoverflow.com/questions/840190/changing-the-current-working-directory-in-java

It would help to know more specifically what you wish to do after changing the directory, but here’s a guess at what you may wish to do:

If you wish invoke purely Lisp-side functionality, then use the value of CL:*DEFAULT-PATHNAMES-DEFAULTS*, which is what UIOP/OS:GETCWD returns.  

If you wish to fork processes in another directory then the specify the relavant argument to  UIOP/RUN-PROGRAM:RUN-PROGRAM.  

In very pathlogical cases you may have to write a script that ensures the JVM hosting ABCL is started in the directory you wish to have as the current directory.  I had to do this in order to get a Minecraft server to run under ABCL.

> Also, what is the set of features that ABCL uses to identify the platform?  On a Mac OSX I see (at a minimum):
> 
> :SWANK 
> :X86-64 
> :UNIX 
> :DARWIN 
> :ARMEDBEAR 
> :ABCL 
> :COMMON-LISP 
> :ANSI-CL 
> :CDR6 
> :MOP 
> :PACKAGE-LOCAL-NICKNAMES 
> NIL
> 

The code which sets platform features is the [best source of what keywords identify which plaform features][2].  Additionaly, there is (incomplete) support for identifying the JVM version by the use of the :java-1.6, :java-1.7, and :java—1.8 keywords.  Again, it would be helpful to know what sort of platform features you wish to detect. 


[2]: https://abcl.org/trac/browser/trunk/abcl/src/org/armedbear/lisp/Lisp.java#L2362


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