File name from file descriptor?

[Chris Gonnerman]

----- Original Message -----
From: <piet at cs.uu.nl>
> >>>>> Carsten Gaebler <clpy at snakefarm.org> (CG) writes:
>
> CG> The problem is this: I have a script that is called like
>
> CG> ./myscript.py < somefile
>
> CG> where somefile is a text file which may or may not be gzipped. To
> CG> determine whether or not the data is gzipped I read in one byte via
the
> CG> gzip module. If that raises an exception I know the data is not
gzipped.
> CG> But I'd miss the first byte if it is gzipped. Yes, I could store this
byte
> CG> somewhere and then pass it around somehow, but ... you know? :-) So
I'd
> CG> like to open a second 'instance' of the file for reading but I only
have
> CG> sys.stdin's file descriptor.
>
> If you are sure that stdin will be a real file you can use:
>
> sys.stdin.seek(0,0)

Somewhere around here <rummage, rummage> I have an old C program I wrote
that does something like this (translated):

    fp = sys.stdin

    try:
        fp.seek(0)
    except IOError:
        tmp = open("tempfile", "w+b")
        tmp.write(fp.read())
        tmp.seek(0)
        fp.close()
        fp = tmp

but then you have to remember to clean up the tempfile afterwards.  If you
are on a Unixoid OS you can add:

        os.unlink("tempfile")

right after the open() call, and the file will be "garbage collected" by
the OS after the interpreter exits.  Don't try that on any OS from Redmond!