On Sat, 2011-10-22 at 06:50 -0200, José Romildo Malaquias wrote:
> %.a : %.txt
> p=$$(cat $< | wc -l)
> q=$$((p+10))
> echo $$q > $@
>
> That is, I want to:
> * set $p to the number of lines in the prerequisite file $<, s
> * set $q to that value plus 10
> * create the target file using $q
GNU make will invoke each separate line of the rule in a different shell
(check the docs).
To do what you want you have to ensure that all the lines are invoked in
a single shell, otherwise the first variable settings have no effect
(they're lost as soon as their shell exits).
Do this with backslash continuations, and adding ";" to separate shell
commands:
%.a : %.txt
p=$$(cat $< | wc -l); \
q=$$((p+10)); \
echo $$q > $@
--
-------------------------------------------------------------------------------
Paul D. Smith <[email protected]> Find some GNU make tips at:
http://www.gnu.org http://make.mad-scientist.net
"Please remain calm...I may be mad, but I am a professional." --Mad Scientist
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