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Article #1269

Re: Determining if an existant file is open

#1269
From: Dan Bernstein
Date: Wed, 21 Nov 1990 19:42
17 lines
1288 bytes
In article <274975C4.21C@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
> According to rwhite@nusdecs.uucp (0257014-Robert White(140)):
> >Do the "put process number in lock file" thing as in uucp.
> This approach cannot be used reliably without either (1) having a lock
> held forever by a dead process, which I find unacceptable, or (2)
> using a kernel locking call, which renders the pid file redundant.

It can be used reliably if you put information like pid and date into
the name of the lock file.

> For you doubters: Once you've determined that a lock file is stale and
> you want to unlink() it, how do you know the lock file hasn't been
> replaced in between the decision to unlink() and the unlink() itself?

The old name will never be reused, so there's no danger of replacement.

---Dan
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Message-ID: <26251:Nov2119:42:1090@kramden.acf.nyu.edu>
Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!kramden.acf.nyu.edu!brnstnd
References: <1990Nov16.023110.1305@csun.edu> <1990Nov16.200945.14468@nusdecs.uucp> <274975C4.21C@tct.uucp>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!kramden.acf.nyu.edu!brnstnd
From: brnstnd@kramden.acf.nyu.edu (Dan Bernstein)
Newsgroups: comp.unix.programmer
Subject: Re: Determining if an existant file is open
Message-ID: <26251:Nov2119:42:1090@kramden.acf.nyu.edu>
Date: 21 Nov 90 19:42:10 GMT
References: <1990Nov16.023110.1305@csun.edu> <1990Nov16.200945.14468@nusdecs.uucp> <274975C4.21C@tct.uucp>
Organization: IR
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