awk/sed/whatever bash question

oshunluvr — Tue, 06 Oct 2026 19:51:09 GMT

I wrote and maintain a set of Dolphin Service Menus to allow some btrfs functionality to be accessible from Dolphin.

I am adding the ability to determine if a "btrfs send|btrfs receive" operation was successful. The success or failure is is indicated by two items retrievable from "btrfs su show". They are "Received UUID:" followed by a UUID and "FLAGS:" followed by "readonly". Both entries are only set if the send|receive operation completes successfully.

One uses the "btrfs su show" action to see the full list of subvolume information, which looks like this:

Code:

sudo btrfs su show @KDEneon_backup
Name:                   @KDEneon_backup
UUID:                   00983575-f97d-d942-9537-f4c8c29bc77a
Parent UUID:            0bef4f24-2620-7443-84d2-43c82a79e690
Received UUID:          16716210-06d4-ea42-9048-7449068cb643
Creation time:          2026-10-06 05:39:35 -0400
Subvolume ID:           2246
Generation:             14825
Gen at creation:        14820
Parent ID:              5
Top level ID:           5
Flags:                  readonly
Send transid:           2145521
Send time:              2026-10-06 05:39:35 -0400
Receive transid:        14821
Receive time:           2026-10-06 05:39:36 -0400
Snapshot(s):
Quota group:            n/a

If the send|receive operation fails, the fields after "Received UUID" and "Flags:" have a dash in them instead of the above.

The question: Is there a preferred or "better" way to extract this information from the above output?

Currently, I'm using:

Code:

RECEIVED_UUID=`sudo -S btrfs su sh $SOURCE | awk 'NR >4 && NR<=5 {print $3}'`
READONLY_FLAG=`sudo -S btrfs su sh $SOURCE | awk 'NR >11 && NR<=12 {print $2}'`

$SOURCE is the full path and filename of the selected subvolume. The above awk statements retrieve the Received UUID and "readonly" from Flags, and it works.

I then use a conditional "if - or" to check for the dash instead of anything else:

Code:

if [[ $RECEIVED_UUID == '-' || $READONLY_FLAG == '-' ]]; then

so if either entry is not set, the script reports that it failed or wasn't a "sent" snapshot.

I feel like there must be a handful of other ways to scrape the info. Mostly, I'm just curious, but having "solid" code is always a good idea.

Thoughts?

Kubuntu Forums - Coding/Scripting

awk/sed/whatever bash question