Valid IDs

[ip1981]

Why are IDs restricted by this pattern?

idRegex = regexp.MustCompile(`^[\w_-]+$`)

https://github.com/opencontainers/runc/blob/master/libcontainer/factory_linux.go#L29

[crosbymichael]

It is for valid filepath names because the container id needs to be written to disk in something like /run to store state.

[ip1981]

File names can include a way more other characters. I fail to see reasons for existing restrictions. foo.com is a valid file name, but not a valid id. Why?