Re: dircat vs. path_concat

["Klaus Schmid" <klaus.schmid@xxxxxxx>]

John E. Davis <davis@xxxxxxxxxxxxx> wrote:
> >Klaus Schmid <klaus.schmid@xxxxxxx> wrote:

> Also, one might want to concatenate
> x:a.dir + b

This should be possible with some additional effort;
as a more complete example:

! x is a logical name defined before
$ define x x1:[x2]
...

% split into directory (x:) and base (a.dir)
(d,b)= split_file( "x:a.dir");

% call system-function f$trnlnm, afair,
% one or more times to resolve to x1:[x2]
d= expand_logical_to_physical( d);

% get child-directory x1:[x2.a]
d= dir_down( d, b);

% dir+base == file
f= d +"b"

> >split_file( "a:[b]c.txt") --> "a:[b]", "c.txt"
> >dir_down( "a:[b]", "c.dir") --> "a:[b.c]"
> >dir_up( "a:[b.c]") --> "a:[b]", "c.dir"
> 
> I think you mean split_file for the last example.

No, not really.

split_file finally just analyzes the string
without any potential failure.

dir_up tries to get the parent-directory and within
that the directory-file, which corresponds to the
input directory. It may fail more or less:
no parent: d=input b=""
parent, but no file: d=parent b=""
e.g.
dir_up("[000000]") --> "[000000]", ""
dir_up("x:") --> "x:", ""
dir_up("") --> "[-]", ""

As pointed out above, I would prefer pure string
operations for the basic path-functions;
some applications will provide many well-formed inputs,
e.g. directory lists, others can expand, translate or
check before.

> I think you can use [] to mean . on VMS, e.g., ./a == []a.  Also, 
> dev$device:[a.b.-] is equivalent to device$device:[a].  I forget what
> dev$device:[a.b...] means.

Ellipsis means current directory including all subdirectories,
e.g. search [a.b...]*.txt sometext.

>  Also it is important to note that on Unix,
> "a/b/.." _may_ not be equivalent to "a".

Hmm. I think I know nothing about this.
Could you give me a hint?
 
> Finally, to make things even more interesting on the VMS side,
> dev$device does not have to represent a single device.  Instead,
> dev$device could represent a search list, i.e., a set of directories
> to be tried in succession.

Never used or heard about the search list before.
Now I found it in a comprehensive documentation on hp-OpenVMS:
http://h71000.www7.hp.com/doc/72final/6489/6489pro.html


Thanks,
-- Klaus

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