For loop in Makefile has no effect
I have a one-line script passed into the foreach
function in a Makefil开发者_C百科e, as shown below:
flag:
$(foreach f, $*.txt, printf "%s\n" 0a "$(grep -o '[0-9]\+' $f | sed 's/.*/read \"&\"/')" "" . w q | ed $f)
What this script line does could be found here. I am just puzzled why it doesn't work this way, because if I put the line into a separate script and call it from the Makefile like this:
flag:
$(forech f, $*.txt, ./script $f)
it works fine.
I also tried the shell for
loop as follows:
flag:
for f in $*.txt ; do \
printf "%s\n" 0a "$(grep -o '[0-9]\+' $f | sed 's/.*/read \"&\"/')" "" . w q | ed $f ; \
done
still no luck. I must touch some subtle points of Makefiles, could anyone enlighten me? Thanks.
Both too many and not enough $ signs! This lists the *.txt files - note the $$F:
all:
for F in *.txt ; do \
echo $$F ; done
The solution is: adding one more $
before the sequence beginning with grep
,
flag:
$(foreach f, $*.txt, printf "%s\n" 0a "$$(grep -o '[0-9]\+' $f | sed 's/.*/read \"&\"/')" "" . w q | ed $f)
or use the old backticks instead
flag:
$(foreach f, $*.txt, printf "%s\n" 0a "`grep -o '[0-9]\+' $f | sed 's/.*/read \"&\"/'`" "" . w q | ed $f)
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