This makefile example should help clear things up:
$ cat makefile
SHELL := bash
.RECIPEPREFIX := >
blah1 := test1
blah2 := test2
export blah2
# blah2 & blah3 should have identical results
export blah3 := test3
default:
>@$(foreach x,blah1 blah2 blah3 blah4 blah5,echo "${x}: (origin = $(origin
${x}), flavor = $(flavor ${x}), make value = ${${x}}, shell value:
$${${x}:-not set})";)
$ make --version
GNU Make 4.1
(...)
$ blah5=test5 make -f makefile blah4=test4
blah1: (origin = file, flavor = simple, make value = test1, shell value:
not set)
blah2: (origin = file, flavor = simple, make value = test2, shell value:
test2)
blah3: (origin = file, flavor = simple, make value = test3, shell value:
test3)
blah4: (origin = command line, flavor = recursive, make value = test4,
shell value: test4)
blah5: (origin = environment, flavor = recursive, make value = test5, shell
value: test5)
This is identical to:
$ export blah5=test5
$ make -f makefile blah4=test4
blah1: (origin = file, flavor = simple, make value = test1, shell value:
not set)
blah2: (origin = file, flavor = simple, make value = test2, shell value:
test2)
blah3: (origin = file, flavor = simple, make value = test3, shell value:
test3)
blah4: (origin = command line, flavor = recursive, make value = test4,
shell value: test4)
blah5: (origin = environment, flavor = recursive, make value = test5, shell
value: test5)
I was a little surprised to discover that variables passed on the
command-line to make get marked for export.
-brian
_______________________________________________
Help-make mailing list
Help-make@gnu.org
https://lists.gnu.org/mailman/listinfo/help-make
