Re: Reading from process pipes in IDL?

[landsman(at)mpb.gsfc.nasa.gov]

In article <39C9CBD4.D6CC859A@mpipsykl.mpg.de>,
  Benno Puetz <puetz@mpipsykl.mpg.de> wrote:
> I have been trying to read image data from compressed (*.gz) files.
>
> While this is possible with
>
>     SPAWN, "gunzip "+file+".gz"
>
>     OPENR, l, file, /GETLUN
>
>     READU, ....
>
>     FREE_LUN, l
>
> I would prefer a way similar to PERL's
>
>     open(FILE, "gzip -cd $file |");
>
>     ...
>
> since it would not have to decompress/compress to disk.
>
> Is this at all possible with IDL?

In V5.3, the /COMPRESS keyword was introduced to OPENR, which allows you
to directly access gzip'ed files in an OS-independent way.   I've been
quite happy with this feature -- you can read compressed files almost
completely transparently.    One thing to watch out for, is that
although POINT_LUN works on compressed files, it is much slower than on
regular files, since IDL always has to reset to the beginning on each
POINT_LUN call for compresed files.

Wayne Landsman                         landsman@mpb.gsfc.nasa.gov


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