Comments (10)
I don't understand what you mean.
I understood what he meant.
from shellcheck.
@koalaman It looks like there are at least 5 ways to get logs ranging from 139.021s to 0.050s.
cron and ssh are system services which journalctl optimizes, services that are not system (or journalctl is unsure of) like postfix* (or anything with a glob) are slow:
# time journalctl -u postfix* | grep -c .
47065
real 2m19.021s
# time journalctl | grep " postfix/" | grep -c .
47484
real 0m20.148s
# time journalctl --system -u postfix* | grep -c .
47065
real 0m7.845s
time journalctl -u [email protected] | grep -c .
47121
real 0m0.727s
# time cat /var/log/maillog* | grep -c " postfix/"
194559
real 0m0.050s
So it looks like glob is the worst offender that should be avoided or at least mitigated with --system.
from shellcheck.
Pretty niche feature ey?
There has been a number of requests like this where someone want to see one command or other get special treatment.
Maybe someone can propose a way to disable a rule given a certain command and let teams have that shellcheck setting in a shared repository to make their life easier or something.
from shellcheck.
systemd is standard, not niche.
Rules are already easy to disable, but there is no reason to ever disable this rule.
from shellcheck.
I think you understand what I mean, but for others:
systemd is not part of any shell internals and have it standout in front of other external programs it need a case. To me it lacks one really.
from shellcheck.
I don't understand what you mean.
There is no such thing as "shell internals", there are "shell builtins" and POSIX,
but the code and goals of ShellCheck do not limit themselves to any minimal set,
and explicitly encourage addressing "corner cases" even less likely to be hit than this.
from shellcheck.
Ok teacher. Present the PR and cross your fingers.
from shellcheck.
On my system, journalctl -u cron > /dev/null
takes 1 second while journalctl | grep cron > /dev/null
takes 48 seconds.
The log is mostly ssh bot traffic, and journalctl -u ssh > /dev/null
takes 63 seconds while journalctl | grep ssh > /dev/null
takes 51 seconds, which is a slight improvement but nowhere near 2 orders of magnitude.
Is this a known issue or something you discovered? It's expected that whichever command you try first will be orders of magnitude slower than the second due to disk caching, so does it hold up under repeated timing?
from shellcheck.
Relatedly the --quiet option should always be used in scripts to avoid the "-- No entries --" spam.
from shellcheck.
I don't know much about systemd, but grep
is obviously less robust and gives different answers in all your example queries. From what I can tell from the source code and setting SYSTEMD_LOG_LEVEL=debug
, journalctl
already expands the glob into matching units rather than doing a different type of scan; -u ssh.service -u ssh.socket
produces the same filter expression as journalctl -u 'ssh*'
. It also doesn't seem like ShellCheck should be suggesting that the user only ever search the system log.
If journalctl
's filtering is objectively suboptimal, then that should likely be fixed on the journalctl
side instead.
Thanks for the suggestion!
from shellcheck.
Related Issues (20)
- Please separate the issue of unused functions from SC2317 (Command appears to be unreachable) HOT 11
- `require-double-brackets` doesn't work in BusyBox `sh` even though `[[` is supported HOT 2
- SC2115 fires when it is statically verifyable that the variable cannot be empty HOT 2
- SC2221/SC2222 fires for non-exhaustive wildcard patterns HOT 1
- SC2154 var is referenced but not assigned not triggered if used within an array HOT 1
- Feature Request: Provide an option to specify the fallback shell type HOT 9
- SC2251 - add ${PIPESTATUS[0]} check to exceptions HOT 1
- [Bug / regression?] In file ignore directives (# shellcheck disable=<check_id>) are not specific & disable all checks instead (not just check_id) HOT 1
- SC2015 inconsistent behavior HOT 2
- Skip SC2015 when it end with: || true
- Please support all alias for busybox shell equally
- SC2154 from strict bash mode example using trap
- SC2086 false positive on readonly integer variable
- SC2004 false positive on assignment to array position HOT 1
- Missing SC2166 URL in summary section HOT 1
- SC2094, SC2035, SC2034, SC2205, SC2283 ternary arithmetic false positives
- RFE: variant of `source=` directive that supports globbing
- SC1090 is sometimes not raised HOT 1
- [Feature request][Bash] Add rules to provide tips on adding local, or readonly status to variables
- If multiple `source` lines are in the same file, all but the first one are ignored
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from shellcheck.