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Path: utzoo!utgpu!water!watmath!clyde!rutgers!gatech!mcnc!xanth!john
From: john@xanth.UUCP
Newsgroups: comp.unix.questions
Subject: Re: access(2) question
Message-ID: <1341@xanth.UUCP>
Date: Thu, 18-Jun-87 19:58:00 EDT
Article-I.D.: xanth.1341
Posted: Thu Jun 18 19:58:00 1987
Date-Received: Sat, 20-Jun-87 01:28:43 EDT
References: <530@applix.UUCP>
Organization: Old Dominion University, Norfolk Va.
Lines: 22
Keywords: access permissions

In article <530@applix.UUCP>, mark@applix.UUCP (Mark Fox) writes:
> Does anybody know why access checks file accessibility using the real [ug]id
> in place of the effective [ug]id? It seems to me that access should agree
> with open(2) as far as whether a program has write or read access to a file.
> Inside a set-uid program that assumption obviously doesn't work while
> uid != euid.

Well, the reason that access was added was to make it possible for a
set[ug]id program to be able to discern whether or not the real user
running it would have access to a certain file.

> Is there a better way of implementing eaccess than using open/close, assuming
> I don't have the file already opened?

Not really.  It doesn't even change the access or update times until
you do a read or write, respectively, so as long as you don't open
O_TRUNC or O_CREAT, you'll be ok.

-- 
John Owens		Old Dominion University - Norfolk, Virginia, USA
john@ODU.EDU		old arpa: john%odu.edu@RELAY.CS.NET
+1 804 440 4529		old uucp: {seismo,harvard,sun,hoptoad}!xanth!john