[brandmeyer]

That's interesting.

Author probably wants to use `private` for those target-local variables, though.

For example,

    R: .SHELLFLAGS := -e
    R: SHELL := Rscript
    R:
        greeting = "bonjour"
        message(paste0(greeting, ", R!"))

Everything that target `R` depends on will also have SHELL and .SHELLFLAGS over-ridden. If `R` depends on some data generated by another program, it probably wants to be built and executed with the default SHELL (or another shell, perhaps).

    R: private .SHELLFLAGS := -e
    R: private SHELL := Rscript
    R:
        greeting = "bonjour"
        message(paste0(greeting, ", R!"))

Now, `R`'s dependencies will be generated with the makefile's defaults.

Usually I prefer to build up richer stages like this using the system shell anyway, though. Build a target which in turn is executed by the shell normally to traverse the next edge in the graph. But I can see how this mechanism has its uses.

See also https://www.gnu.org/software/make/manual/html_node/Target_00...

[sciencerobot]

I didn't know about private. Thanks for the tip.