From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-16.italiaonline.it ([212.48.25.144]:35883 "EHLO libero.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751377AbbJEPm4 (ORCPT ); Mon, 5 Oct 2015 11:42:56 -0400 Reply-To: kreijack@inwind.it Subject: Re: [PATCH 4/4] btrfs-progs: change -t option for subvolume list to print a simple space-separated table (making it machine-readable) References: <1443804083-876-1-git-send-email-axel@tty0.ch> <1443804083-876-5-git-send-email-axel@tty0.ch> <560FA665.6000700@libero.it> <560FA944.3050606@digint.ch> <5610134D.9070807@inwind.it> <561138F4.5090105@inwind.it> <56129171.4040200@digint.ch> To: Axel Burri Cc: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org From: Goffredo Baroncelli Message-ID: <56129A7C.8060701@inwind.it> Date: Mon, 5 Oct 2015 17:42:52 +0200 MIME-Version: 1.0 In-Reply-To: <56129171.4040200@digint.ch> Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi Axel, On 2015-10-05 17:04, Axel Burri wrote: [...] > > A quick look at the code shows me that Goffredo is right here, as > __list_subvol_search() always fetches ALL data from > BTRFS_IOC_TREE_SEARCH, putting it into a rbtree for later processing > (assemble full paths, sorting). > > While there is certainly room for improvements here (assuming that > BTRFS_IOC_TREE_SEARCH returns objectid's in sorted order, it would > definitively be possible to produce line-by-line output), the code looks > pretty elegant the way it is. > > I still don't think it is wise to bloat things further just for printing > nice tables. My impression is that "btrfs subvolume list" is > human-readable enough without the '-t' flag, while the output with '-t' > flag is much more machine-readable-friendly, and thus should have the > highest possible performance. e.g.: I disagree, the "-t" mode is for the human; the non '-t' mode would be for machine (if you take the space as separator and the first word as key, with the exception of the path which starts from the "path " word and ends to the end of line); unfortunately "top level" is an exception. Anyway btrfs is not very machine-friendly (sic). Compare the two output below: $ sudo btrfs sub list -a / ID 257 gen 44309 top level 5 path /debian ID 289 gen 17415 top level 257 path debian/var/lib/machines ID 298 gen 35434 top level 5 path /debian-i32 ID 299 gen 43961 top level 5 path /boot ID 300 gen 39452 top level 5 path /debian-jessie $ sudo btrfs sub list -at / ID gen top level path -- --- --------- ---- 257 44310 5 /debian 289 17415 257 debian/var/lib/machines 298 35434 5 /debian-i32 299 43961 5 /boot 300 39452 5 /debian-jessie I think that is easy to declare the latter more "human" friendly. BTW with the use of the table_* function the output become: $ sudo ./btrfs sub list -at / ID gen top level path === ===== ========= ======================= 257 44311 5 /debian 289 17415 257 debian/var/lib/machines 298 35434 5 /debian-i32 299 43961 5 /boot 300 39452 5 /debian-jessie $ sudo ./btrfs sub list -aptcguqR / ID gen cgen parent top level parent_uuid received_uuid uuid path === ===== ===== ====== ========= =========== ============= ==================================== ======================= 257 44313 7 5 5 - - 840c86cf-e78b-d54a-ab38-66662858812d /debian 289 17415 17415 257 257 - - 8b857250-3a3e-754d-810e-57342bbb2f56 debian/var/lib/machines 298 35434 35399 5 5 - - 1f38049b-b153-d741-b903-d2de6fd7b3fd /debian-i32 299 43961 35512 5 5 - - f9d52b6b-a6d1-8c45-a6cd-ddb68cf58062 /boot 300 39452 37744 5 5 - - 026e44bd-66d4-e341-9a14-0124acf79793 /debian-jessie I right aligned each field with the exception of the path (which is left aligned). I already prepared the patch which convert "btrfs sub list -t" to use the table_* function. If you want I can send it to you to extend/replace your patch #4. BR G.Baroncelli > > btrfs sub list -t / | (read th; while read $th ; do echo $gen; done) > btrfs sub list -t | column -t > > Again, this is just my opinion, being a "unix-purist". Maybe a good > compromise would be to use a single "\t" instead of " " as column delimiter. > -- gpg @keyserver.linux.it: Goffredo Baroncelli Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5