Find parent directory of file

[cormullion]

Given a file coming in through the command line:

Code: Select all

(set 'f (main-args 2))

How can I find out what the directory of it is so that I can set the current directory to it?

Code: Select all

(change-dir ... f)

The only thing I can see to do is to parse the filename, which seems like the non-newLISP way...

[Lutz]

you could use real-path to get the full path and then isolate the path chopping off the filename from the end:

Code: Select all

(join (chop (parse (real-path (main-args 2)) "/")) "/")

Lutz

[cormullion]

Thanks, Lutz! I was trying things like parse and even stuff like:

Code: Select all

(reverse (member "/" (reverse (real-path f) )))

Yours looks more sensible.

I can imagine a more elegant solution one day - like if change-dir accepted a filename and found the containing directory ...

[Sammo]

Following Lutz's lead, in Windows I can define:

Code: Select all

(define (.. f)
  (join (chop (parse (real-path f) "\\") 2) "\\") )

(define (. f)
  (join (chop (parse (real-path f) "\\") 1) "\\") )

Then execute:

Code: Select all

(change-dir (.. "c:\\path1\\path2\\path3\\filename.txt"))

to change the directory focus to c:/path1/path2, or:

Code: Select all

(change-dir (. "c:\\path1\\path2\\path3\\filename.txt"))

to change the directory focus to c:/path1/path2/path3.

Something along these lines might be the ticket.

[cormullion]

Hi Sammo - nice to see you round here! I hadn't thought about the Windows backslash. Doesn't Windows now accept forward slashes? (Sorry I rarely use it at the moment.) So a generic function would be harder.

I like the idea of defining '..' and '.' as functions...