Fail stating a file not in current folder

Fail stating a file not in current folder

[zulian jc]

Hello guile list,

I am new to guile and scheme so excuse my poor coding. Anyway I am faced with 
a little problem with guile 1.8.1. I am writing a function that collects all 
sub-directory from a given directory. To do this I am using the opendir and 
readdir functions. However it happens that if I am not cd'ing into the 
directory I want to browse, the following function failed. Is that a normal 
behavior?

(define gather-dirs
  (lambda (path)
    ;; with the following line commented out the function will fail browsing
    ;; directories other than the current one
    ;;(chdir path)
    (let ((cdir (opendir path))
          (l '()))
      (do ((entry (readdir cdir) (readdir cdir)))
        ((eof-object? entry) l)
        (if (directory? entry)
            (set! l (cons entry l)))))))

(define directory?
  (lambda (x)
    (eq? (stat:type (stat x)) 'directory)))

Here is the error I get back:
ERROR: In procedure stat:
ERROR: No such file or directory: ".bb"

Note: '.bb' is a folder that exist in the folder I want to browse but not in 
the current one. So basicaly 'readdir' and 'opendir' did their job fine but 
when I am trying to stat on the found entry it fails (in the 'directory?' 
function).

Investigating further I saw that 'readdir' just return a string with the name 
of the folder entry, that is a name relative to the folder opened 
by 'opendir'. Say I am browsing '/home/bob' folder then readdir will return 
me as an entry "bin" and not "/home/bob/bin". Hence 'stat' is failing if 
there is no 'bin' folder in current folder. Is that correct?

Now how could one browse a folder and stat on each entry without having to 
change to that folder?


Thanks in advance for your help,
jc

Re: Fail stating a file not in current folder

[Neil Jerram]

2008/9/17 zulian jc <jzu@imtf.ch>:
> Hello guile list,

Hi!

> I am new to guile and scheme so excuse my poor coding. Anyway I am faced with
> a little problem with guile 1.8.1. I am writing a function that collects all
> sub-directory from a given directory. To do this I am using the opendir and
> readdir functions. However it happens that if I am not cd'ing into the
> directory I want to browse, the following function failed. Is that a normal
> behavior?

Yes, because of what you have suggested...

> (define gather-dirs
>  (lambda (path)
>    ;; with the following line commented out the function will fail browsing
>    ;; directories other than the current one
>    ;;(chdir path)
>    (let ((cdir (opendir path))
>          (l '()))
>      (do ((entry (readdir cdir) (readdir cdir)))
>        ((eof-object? entry) l)
>        (if (directory? entry)
>            (set! l (cons entry l)))))))
>
> (define directory?
>  (lambda (x)
>    (eq? (stat:type (stat x)) 'directory)))
>
> Here is the error I get back:
> ERROR: In procedure stat:
> ERROR: No such file or directory: ".bb"
>
> Note: '.bb' is a folder that exist in the folder I want to browse but not in
> the current one. So basicaly 'readdir' and 'opendir' did their job fine but
> when I am trying to stat on the found entry it fails (in the 'directory?'
> function).
>
> Investigating further I saw that 'readdir' just return a string with the name
> of the folder entry, that is a name relative to the folder opened
> by 'opendir'. Say I am browsing '/home/bob' folder then readdir will return
> me as an entry "bin" and not "/home/bob/bin". Hence 'stat' is failing if
> there is no 'bin' folder in current folder. Is that correct?
>
> Now how could one browse a folder and stat on each entry without having to
> change to that folder?

You can use `in-vicinity' to form a relative path name from the
working directory.  Your code above should work if you change the
(directory? entry) call to:

 (directory? (in-vicinity path entry))

Regards,
         Neil