What's this for?
When you need to see the output from all changed files within a directory.
Why doesn't tail -f /var/logs/* work?
Unfortunately, tail -f /logs/* may not do what you want it to do. Bash will expand * to all existing files within /logs/ and then show the extra lines added to each of them.
It also will not recurse down, any levels deeper than the current directory.
How is fstail different then?
fstail uses the gopkg.in/fsnotify to detect both new files, and existing files that are changed. It then starts concatenting their contents to the terminal.
I needed this for actuated.dev which launches microVMs on servers for CI.
Each VM launched will create a different file at: /var/log/actuated/GUID.txt, and tail -f * would only find existing files.
Tail the current directory:
cd /var/log/actuated
fstail
[7cd0d139b24d9cd30e3ad9ce7afcfe5999d2bf20.txt] [ 12.770522] bash[1191]: 2023-03-22 11:04:00Z: Running job: arkade-e2e (run-job)
[49c8f4be774730ff6e5070166fc34ac25dc0e320.txt] [ 13.363398] bash[1183]: 2023-03-22 11:04:00Z: Running job: arkade-e2e (k3sup)
To turn off the file prefix, set FS_PREFIX=0.
[ 12.770522] bash[1191]: 2023-03-22 11:04:00Z: Running job: arkade-e2e (run-job)
[ 13.363398] bash[1183]: 2023-03-22 11:04:00Z: Running job: arkade-e2e (k3sup)
Tail files in a given directory:
fstail /var/log/nginx/
By default, the base filename is going to be printed as a prefix for each tailed file:
1e51959055fb132720d03584388b5ac738689798.txt | Booting Linux Kernel.. OK
13d461e989733fa0f75df5227debab4be3504726.txt | Shutting down in 30s... To suppress the prefix, run the command with FS_PREFIX=0.
The kubelet with K3s will create log files for containers in /var/log/containers with long prefixes, the FS_PREFIX=k8s env-var can be used to redact the string.
Any text passed after the folder forms a grep for the filenames, so here, we are only looking at "queue-worker" containers.
Note that these files do not receive a "WRITE" fsnotify event, only an initial "CREATE".
FS_PREFIX=k8s sudo -E fstail /var/log/containers/ "queue-worker"
2025/03/12 07:39:23 Attaching to: queue-worker-6b579d58d7-krgx5_openfaas_queue-worker-08e45f83b4f6edbd9ae2182f6709ccfb28e3e5871b5cc0d303c20c4c7b2a3d56.log
2025/03/12 07:39:23 Attaching to: queue-worker-6b579d58d7-krgx5_openfaas_queue-worker-f03309cc46a9752a4366062da18872ee215cc1837dcb335fa0d339948f3d9609.log
queue-worker-6b579d58d7-krgx5| 2025-03-10T12:40:45.84048421Z stderr F 2025-03-10T12:40:45.838Z info jetstream-queue-worker/main.go:118 JetStream queue-worker {"version": "0.3.46", "gitCommit": "8320975de6c98c8b6ef6781e2db610cc389c7e33"}
queue-worker-6b579d58d7-krgx5| 2025-03-10T12:40:45.840510746Z stderr F 2025-03-10T12:40:45.838Z info jetstream-queue-worker/main.go:120 Licensed to: Alex Ellis
queue-worker-6b579d58d7-krgx5| 2025-03-10T12:40:45.840514335Z stderr F
queue-worker-6b579d58d7-krgx5| 2025-03-10T12:40:45.840517017Z stderr F 2025-03-10T12:40:45.839Z info metrics/metrics.go:79 Starting metrics server on port 8081Download a release binary:
Or download via arkade:
curl -SLs https://get.arkade.dev | sh
arkade get fstailOr install via Go to install from source:
go install github.com/alexellis/fstailIf you need Go on a Linux system:
curl -sLS https://get.arkade.dev | sudo sh
sudo arkade system install go
If you wish to build multi-arch binaries on your own machine:
make distCopyright Alex Ellis 2023
MIT license.