How to check whether GNU Make supports Guile

问题:

How to check from the command line whether GNU Make is built with support of Guile?

Inside Makefile it can be determined via analyzing .FEATURES variable (see documentation).

回答1:

As @ruvim points out, the manual says

You can determine whether GNU Guile support is available by checking the .FEATURES variable for the word guile.

$(if $(filter guile,${.FEATURES}) \
  ,$(info Guile suppoerted, yay!) \
  ,$(error Guile not supported - update your make))

回答2:

One possible way is a quasi makefile in stdin.

So, .FEATURES variable can be printed in the following way:

echo '$(info $(.FEATURES))' | make -f -

The following command outputs guile string if it is supported or nothing in otherwise:

echo '$(info $(filter guile,$(.FEATURES)))' | make -f -  2>/dev/null

A variation using grep:

echo '$(info $(.FEATURES))' | make -f - 2>/dev/null | grep -wo guile

The solution

As @bobbogo mentioned, we can avoid the pipe at all, using --eval option:

make --eval '$(info $(filter guile,$(.FEATURES)))' 2>/dev/null

This command will print 'guile' or nothing.