Re: OS.FileSys and recursive procedures ?

Hi John,

The following code just doesn't work as expected...

     fun loopDir(dir_name) =
         let val d = FS.openDir(dir_name)
             fun entries() =
                 let val r = FS.readDir(d)
                 in
                     case r of
                         NONE => print "NONE\n"
                       | SOME s =>
                         (if FS.isDir(s) then
                              print ("DIR:"^s^"\n")
                          else if FS.isLink(s) then
                              print ("LINK:"^s^"\n")
                          else
                              print ("FILE:"^s^"\n");
                          entries())
                 end
         in
             entries()
         end

The idea, of course, is that entries loops until NONE comes back.

I run the above using something like :

loopDir(path)

It always succeeds on the first readDir and then ALWAYS fails on the  
second readDir.

However if I do a :

chDir(path)
loopDir(path)

Then it works as expected.

???

Brian

On Jan 22, 2006, at 9:22 PM, John Reppy wrote:

> Are you sure that you have read and execute permission on the  
> directory in
> question?
>
> 	- John
>
> On Jan 22, 2006, at 11:06 PM, brian denheyer wrote:
>
>> The following function does not seem to work correctly :
>> (you'll need structure FS = OS.FileSys to make it run)
>>
>>     fun loopDir(dir) =
>>         (print "loopDir\n";
>>          let val d = FS.readDir(dir)
>>          in
>>              case d of
>>                  NONE => (print "none\n";
>>                           FS.closeDir(dir))
>>                | SOME s => (if FS.isDir(s) then
>>                                 (print ("Dir:'"^s^"'\n");
>>                                  print ("full path:"^FS.fullPath(s) 
>> ^"\n");
>>                                  loopDir(FS.openDir(s));
>>                                  ())
>>                             else if FS.isLink(s) then
>>                                 print ("Link:'"^s^"'\n")
>>                             else
>>                                 (print ("File:"^s^"\n");
>>                                  File(s));
>>                             loopDir(dir))
>>
>>          end
>>
>> I start the loop with loopDir(FS.openDir("."))
>>
>> Eventually I get a file doesn't exist error !
>> Through the use of the prints I have identified that the val d =  
>> statement is
>> failing with a "no such file or directory error".
>>
>> That's pretty much impossible as far as I can tell.  Notice that  
>> the openDir
>> has already been done and is being passed into the loop.  The only  
>> possible answers
>> are a file of some sort, or NONE, the openDir has already been  
>> performed and the directory mus exist or the FS.isDir would not  
>> have succeeded.
>>
>> It's definitely the recursive invocation which is causing  
>> problems.  In other words,
>> if I perform the readDir BEFORE recursively invoking the loop, it  
>> is sucessful
>> and gives the expected results.
>>
>> This is on MAC OS X 10.4.4
>>
>> Thanks
>>
>> Brian
>>
>> P.S. Is this list still alive ?  have not seen anything in a long  
>> time...
>>
>>
>>
>>
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>
>
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