Hi Zack, and many thanks for the thorough answer ! > This is an easy mistake to make. Remember that configure.ac is an M4 > script, that generates a shell script, configure. When configure is > run, M4 is no longer around to help out. You're right ; shell variables are only available when running "./configure", when it is far too late... it is so obvious now, that I'm facepalming myself. > So you can't mix M4 and shell like the above. Instead, you can do it all in M4: > or you can do it all Yes, since it is a ad-hoc solution and it is a lot easier to read, shell syntax is definitely better for my usecase. I've just implemented it by using AS_ECHO, and a grep/sed logic as you suggested. Seems to work fine. Thanks a lot Zack ! Regards, *Manuel Bachmann, Graphics & Multimedia Engineer www.iot.bzh <http://iot.bzh> * 2016-06-06 15:31 GMT+02:00 Zack Weinberg <zackw@xxxxxxxxx>: > On Mon, Jun 6, 2016 at 5:17 AM, Manuel Bachmann <manuel.bachmann@xxxxxxx> > wrote: > > Hi folks, > > > > I am trying to use the "m4_bpatsubst" and/or "patsubst" macros (which I > > found documented here : [1] [2]), to remove a string from a variable in > my " > > configure.ac" ; and pass it to "Makefile.am", so it ends up in final > > "Makefile". > > > > I was able to get some kind of output, with this in "configure.ac" : > > > > VAR="text1 text2" > > VAR2=m4_bpatsubst("$VAR", "text1") > > AC_SUBST(VAR2) > > This is an easy mistake to make. Remember that configure.ac is an M4 > script, that generates a shell script, configure. When configure is > run, M4 is no longer around to help out. (This is an intentional > design decision; it was, many years ago, not considered appropriate to > require people to have M4 available when running configure.) > > So you can't mix M4 and shell like the above. Instead, you can do it all > in M4: > > m4_define([VAR],[text1 text2]) > m4_define([VAR2],[m4_bpatsubst([VAR1],[text1],) > [VAR2=]VAR2 > AC_SUBST([VAR]) > > or you can do it all in shell: > > VAR="text1 text2" > VAR2="`AS_ECHO("$VAR") | sed 's/text1//g'`" dnl yes, the nested double > quotes are correct > AC_SUBST([VAR2]) > > You probably want to do it all in shell. The only situation I can > think of where you would want the all-in-M4 version is if you were > implementing a new Autoconf macro, VAR came from one of its arguments, > and it was guaranteed to be literal text - not the result of any > configure-time processing - in the caller. > > zw > _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx https://lists.gnu.org/mailman/listinfo/autoconf
