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Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!ames!haven!ncifcrf!nlm-mcs!adm!smoke!gwyn
From: gwyn@smoke.ARPA (Doug Gwyn )
Newsgroups: comp.unix.questions,comp.lang.c
Subject: Re: General Unix/C question
Keywords: userid Make su segmentation core
Message-ID: <8452@smoke.ARPA>
Date: 8 Sep 88 05:07:50 GMT
References: <641@jura.tcom.stc.co.uk> <794@philmds.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 11

In article <794@philmds.UUCP> leo@philmds.UUCP (Leo de Wit) writes:
-|Below is the program I use to run a unix command ...
-            2) when you start the program the input/output redirection is
-done, perhaps by your shell. This means that these input/output streams
-must be readable/writable by the current uid/gid; when you setuid &
-setgid the process may not be allowed anymore to write these
-descriptors.

On UNIX, the permissions are checked when the files are opened,
not on each read and write.  If the files got opened okay then
they should remain usable after the set*id() calls.