Re: Cache commands output

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Re^2: Cache commands output by wangcong (Initiate) on Oct 20, 2008 at 15:36 UTC
Thanks for your reply, kyle. What I want to cache is the output of some command, not a file, so that is not what I want. :)	[reply]
Re^3: Cache commands output by kyle (Abbot) on Oct 20, 2008 at 15:48 UTC
You can certainly cache the output of some command with Cache::FileCache. `sub qx_cache { my $cmd = shift; my $cache = Cache::FileCache->new({ namespace => $0 }); die 'no cache' if ! $cache; my $out = $cache->get( $cmd ); if ( ! defined $out ) { $out = qx{ $cmd }; $cache->set( $cmd, $out ); } return $out; }` [download] You can set a timeout value when you call `set()`. Any `get()` on a key that's expired will come back undef.	[reply] [d/l] [select]
Re^4: Cache commands output by Anonymous Monk on Oct 22, 2008 at 13:24 UTC
Thanks, everyone! I will try Cache::FileCache. :)	[reply]
Re^3: Cache commands output by RatKing (Acolyte) on Oct 20, 2008 at 15:54 UTC
I think kyle was right, what you want is Memoize This caches the result of a function by storring its return value in a hash, so the next time you call the function with the same parameters it will look up the return value in the hash and return that for you, rather then run the whole thing again. It also gives you the option to list the full hash so you can shove that in a file or database and load it again the next time you start your script resulting in lightning fast performance of a normally very slow fucntion, assuming you use the same input, which you must or caching makes no sense at all.	[reply]
Re^4: Cache commands output by kyle (Abbot) on Oct 20, 2008 at 16:14 UTC
One difference between using Memoize and Cache::FileCache is that the former defaults to caching forever while the latter can have an expiration time. The OP seems to be looking for some kind of expiration in the implementation. To do that with Memoize, I think you'd have to import `unmemoize` and write the expiration manually (but I could be wrong).	[reply] [d/l]
Re^3: Cache commands output by blazar (Canon) on Oct 21, 2008 at 09:22 UTC
I personally believe that this doesn't make sense, since the in root node you clearly say: "My idea is using temporary files for each command output, and use the time stamp of each file to know if that output is out of date or not." So basically it seems you want a form of caching/memoizing that is persistent across program invocations, and manages expiration dates. Cache::FileCache appears to do exactly this; in particular if you did care to read the very description "section" (it's one line!) of its documentation, then you would have found that: The FileCache class implements the Cache interface. This cache stores data in the filesystem so that it can be shared between processes. The additional emphasis is mine: please note that it talks about data which is agnostic wrt whered does it come from, be it a "command" or whatever... `--` If you can't understand the incipit, then please check the IPB Campaign.	[reply] [d/l]