Some of my environment variables ($PATH, $MANPATH and friends) are partially set up in different source files.

I find myself wishing for a command or method to quickly gather what part, in a specific environment variable, came from what file.

My $PATH, for instance, has obviously been set (added to) in .bashrc, /etc/paths, /etc/paths.d/X11 … and I'm still looking for that last mysterious file which superfluously created a duplicate path definition in my $PATH.

It takes a good while to manually pinpoint the files that contribute to environment variables. There must be a useful way to bypass this unnecessary labor of tracing all the setters … or am I the only one thinking along these lines?