How to schedule for every two fridays with cron and/or at?

[Mike Fedyk]

Sam Varshavchik wrote:

> Mike Fedyk writes:
>
>> Hi,
>>
>> I have Amanda setup to run a daily backup Monday through Friday 
>> night.  That works fine.
>>
>> But now I want to add a full backup every two weeks on Friday night 
>> and I'm having trouble creating cron entries that don't have the 
>> commands running on the same day for full and daily backups.
>>
>> The best I have come up with is to run "at 20:45 Friday + 14 days" 
>> and "at 20:45 Friday + 28 days" at the beginning of each month but I 
>> don't think that will handle the situation correctly if the weeks 
>> don't overlap correctly.
>>
>> Any ideas on how to get this working would be very helpful.
>
>
> Run the following script every Friday:
>
> if test -f /etc/foo
> then
>     rm -f /etc/foo
> else
>     touch /etc/foo
>     exit 0
> fi

Ok, thanks.  I'm going to modify it to take two arguments.  One for temp 
file specification, and one for command to alternate.

And I'll call it "alternate"

Now that I'm doing that, does anyone know of a project that collects and 
maintains a bunch of little utilities like this?  Like a sysadmin 
toolbox or something...