Re: Curious FindFile behavior

[Dick Jackson <djackson(at)attcanada.net>]

Barry Lesht wrote:
> 
> I'm running IDL5.1 on an SGI (IRIX6.2).  I'm using FindFile to create
> an array of data filenames that I can pass to some processing code.
> There are (as it turns out) 515 files in the directory I'm searching.
> The filenames are all of the form xxxxxxxxx.xx.yymmdd.hhmmss.cdf. I
> get the following from FindFile-
> [...]
> IDL> files=FindFile('*.cdf', COUNT=nf)
> IDL> PRINT, nf
>            0
> [...]
> IDL> files=FindFile('*980*.cdf', COUNT=nf)
> IDL> PRINT, nf
>          425
> [...]
> Can anyone explain this?  Thanks.

Barry,

I recall seeing cases in IRIX where the result of a system call, if it
is too large, ends up coming back completely empty instead! From what
you've said, the result of 'ls *.*' or some such command would be at
least 15K of text, but less for the last two, as there are fewer files
to list. There may be a limit in between somewhere. (16KBytes, perhaps?)

I don't know if you can test this limit at the IRIX prompt, it may only
happen when the result is piped into a program such as IDL. Sorry, I
don't run IRIX anymore, so I can't test this.

One upshot of this is that you would get fewer 'findable' files if you
started higher up in the directory tree, since each of the file names
would be longer. This can indeed be frustrating.

A competent IRIX sysadmin would likely know more about these limits, and
whether this is the problem at all.

Cheers,
-- 
-Dick

Dick Jackson             Fanning Software Consulting, Canadian Office
djackson@dfanning.com    Calgary, Alberta   Voice/Fax: (403) 242-7398
    Coyote's Guide to IDL Programming: http://www.dfanning.com/