ci: add shell linting workflow

[grische]

A proposal to add some shell linting as there are quite some shell scripts in this repository.

[maurerle]

As this affects more than the packages I am responsible off, I think at least someone else should be aware and approve this change?

I think it is quite good

[grische]

Yeah, this will cause a considerable amount of warnings/errors the next time someone touches a shell script. I can go ahead and fix (most of) them if needed beforehand.

[herbetom]

Is there a link where one can see which scripts (in which way) this will affect? I've got no idea wheter shellcheck is a fitting choice for this repo.

And yes, i think fixing those scripts should be done beforehand and not by the next person who finds themself in the unfortunate situation to trigger that workflow ;)

[grische]

Shellcheck helped me identify a range of bugs in the ssid-changer script, so I do think that it is a helpful addition in general.

You can run this command locally, that roughly does what the action does:

shellcheck $(find . -type f -print0 | xargs -0 awk 'FNR==1 && /^#!.*sh/ { print FILENAME }')

[maurerle]

I did run:

shellcheck -f diff $(find . -type f ! -path './.git/*' -print0 | xargs -0 awk 'FNR==1 && /^#!.*sh/ { sub(/^.{2}/, "", FILENAME); print FILENAME }') | git apply

to auto fix some issues - but most have to be solved manually.

There are still a lot here: shellcheck $(find . -type f -print0 | xargs -0 awk 'FNR==1 && /^#!.*sh/ { print FILENAME }')
I think some are quite verbose like
^-- SC3014 (warning): In POSIX sh, == in place of = is undefined.
SC1091 (info): Not following: /lib/gluon/autoupdater/lib.sh was not specified as input
^-------^ SC2034 (warning): USE_PROCD appears unused. Verify use (or export if used externally).

and the like.. I don't think that it is beneficial to have a lot of shellcheck workarounds though :D
Do you have a neat solution for this? @grische just ignore SC2034 for example?

[grische]

Added exemplary PRs that fix the shellcheck issues in the ffac-ssid-changer package:

• ffac-ssid-changer: fix shellcheck issues #54
• ffac-ssid-changer: replace string indexing #55
• ffac-wg-registration: fix all shellcheck issues #56

[grische]

Regarding ^-- SC3014 (warning): In POSIX sh, == in place of = is undefined., this is a real warning, as this does not work across multiple shells:

ash

X=1
[ $X = 1 ]
[ $X == 1 ]
ash: 3: [: 1: unexpected operator

dash

X=1
[ $X = 1 ]
[ $X == 1 ]
dash: 3: [: 1: unexpected operator

ksh, bash or busybox sh

X=1
[ $X = 1 ]
[ $X == 1 ]

Shellcheck has support for full bash, ksh and dash, but not the full set for busybox sh. It interprets busybox sh as ash and ash in turn as dash:
https://www.shellcheck.net/wiki/SC1071

[grische]

I opened an issue with shellcheck to see if it can be improved for our use-case here:
koalaman/shellcheck#2865

[grische]

I opened PRs for all outstanding shellcheck issue and assigned it to the "suggested" reviewer from Github:

• ffac-mesh-vpn-wireguard-owrt19: fix all shellcheck issues #57
• ffac-weeklyreboot: fix all shellcheck issues #60
• ffgraz-ddhcpd-batman-adv: fix shellcheck issues #61
• ffmuc-mesh-vpn-wireguard-vxlan: fix all shellcheck #62
• ffda-network-setup-mode: fix all shellcheck issues #63
• ffda-usb-wan-hotplug: silence SC2034 for init.d #64
• ffgraz-blink: fix shellcheck issues #65
• ffgraz-config-mode-at-runtime: fix all shellcheck #66
• ffgraz-yggdrasil: fix shellcheck #67
• ffgraz-config-mode-theme-funkfeuer: fix shellcheck #68
• ffgraz-ddhcpd: silence shellcheck issues #69

These PRs should address all shellcheck issues.

[grische]

@maurerle @herbetom @neocturne except the #61, all shellcheck issues should be resolved now and the CI passes at least on my local machine.