suggestion for plugin.sh:clean_fieldname

[bokutin]

I noticed this when using plugins/munin_update.

munin/plugins/node.d/munin_update

Line 107 in 091c8e6

name="$(clean_fieldname "$i")"

clean_fieldname 4thhost -> _thhost
clean_fieldname 5thhost -> _thhost

This does not work.

munin/plugins/plugin.sh

Line 13 in 091c8e6

echo "$@" | sed -e 's/^[^A-Za-z_]/_/' -e 's/[^A-Za-z0-9_]/_/g' -e 's/^root$/__root/'

We feel the following should be done even if it affects us globally.
This would not be something to write into each plugin.

echo` "$@" | sed -e 's/^[0-9]/_&/' -e 's/^[^A-Za-z_]/_/' -e 's/[^A-Za-z0-9_]/_/g' -e 's/^root$/__root/'

We would appreciate your consideration.

[kenyon]

Having clean_fieldname output a valid fieldname even if the input starts with a number seems like a good idea.

For reference, the field name restrictions are documented here: https://guide.munin-monitoring.org/en/latest/reference/plugin.html#notes-on-fieldnames

[bokutin]

Thanks for pointing that out.

clean_fieldname seems to have this behavior since the first commit around 2006.

I hesitate to easily change a code that has a long history.

But it is also true that the plugin munin_update does not work on hosts with munin.conf written as shown below.

[myhost;4thhost]
    ...
[myhost;5thhost]
    ...

That said, should we be aware of this before clean_fieldname in all plugins...