Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.UUCP
Newsgroups: comp.unix.questions
Subject: Re: File descriptors
Message-ID: <5875@brl-smoke.ARPA>
Date: Thu, 21-May-87 05:09:28 EDT
Article-I.D.: brl-smok.5875
Posted: Thu May 21 05:09:28 1987
Date-Received: Sat, 23-May-87 01:13:53 EDT
References: <2532@ncoast.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 10

In article <2532@ncoast.UUCP> robertd@ncoast.UUCP (Rob DeMarco) writes:
> Can some one tell me what a "File Descriptor" is? Thank you.

It's just an index into an open-file table maintained inside the
kernel; the open-file table is used to keep track of the state of
the open file (such as, where is the actual data, and how far into
the data is the file position pointer associated with this F.D.).
Think of it as a "handle" on the file that the kernel gives you when
you open it.  For further information read Ken Thompson's "UNIX
Implementation" (used to be in Vol. 2 of the UNIX manual set).