OT: cat and tail

[Scott Haneda]

On Dec 18, 2009, at 8:08 PM, Brandon Allbery wrote:

> On Dec 18, 2009, at 23:02 , Scott Haneda wrote:
>> # make a copy of the file and also clear it cd /path/to/ cat  
>> running_log > stale_log && echo "" > running_log
>
>
> mv running_log running_log.old && touch running_log && cat  
> running_log.old >stale.log

Mind breaking that out for me?
If running_log is basically a live copy of another log, always being  
written to, and a mv (rename) it, I assume that running_log.old still  
gets written to? The OS keeps writing my tail command to it, even  
though the name has changed?

Then the double && which seems a AND operator to me, never seen it in  
this use case before.  Next up, you crate a file running_log, which  
will be empty, and shove the running_log.old contents into the  
stale.log.  I think I need to rm running_log.old as well?

But this all depends on the tail command continuing to write to a log  
file even though it has been renamed.  I assume this is near always  
the case, which is why I generally have to sleep apache on a log roll,  
and let those last open connections clean themselves up?

I will do a few little tests, thanks for the pointers.
-- 
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