[ale] flock

cfowler cfowler at outpostsentinel.com
Mon Mar 26 08:35:27 EDT 2007


Isn't flock advisory locking?  Maybe vipw uses it?  In order for it to
work both programs must use flock.

On Mon, 2007-03-26 at 07:12 -0400, James P. Kinney III wrote:
> Hmm. I ran the following test:
> 
> su
> flock -x /etc/passwd -c `sleep 60`
> 
> Then from a different window I was _STILL_ able to vipw and save a
> change before the sleep ran out.
> 
> So flock from bash does NOT work as desired.
> 
> -testing perl's flock next-
> 
> On Sun, 2007-03-25 at 23:35 -0400, James P. Kinney III wrote:
> > I need to put an exclusive lock on a couple of files during a process to
> > make sure they are not written to during the script run. I'm unclear on
> > the use of flock within bash.
> > 
> > What I _want_ to do is
> > 
> > lock file(s)
> > extract data from the locked file
> > do more stuff (i.e. get mtime on locked file, etc)
> > unlock file(s)
> > 
> > Reading the man pages on flock are not helping. It _looks_ like:
> > 
> > flock -x <file-to-lock> -c <external-script-that-processes-stuff>
> > 
> > will do it but I can't figure out a way to test this.
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