gfortran include path -- is there an alternative to passing multiple -I options?
fortran, gcc, gfortran, include, path
Solution
As far as I know `gfortran` does not support this, which is quite annoying. But it is possible to work around it. If you name the following script `gfortran` and put it in a directory in your `$PATH` that is searched before the one with the real `gfortran` in it, then you will have the behavior you want, with `$CPATH` transparently being expanded into -I arguments:
#!/bin/bash
/path/to/gfortran $(for i in ${CPATH//:/ }; do echo -I"$i"; done) "$@"
Remember to mark it as executable. For example, if my `$PATH` is `/home/amaurea/local/bin:/usr/local/bin:/usr/bin:/bin` and `gfortran` lives in `/usr/local/bin`, I would set it up as
$ cd /home/amaurea/local/bin
$ cat <<HERE > gfortran
#!/bin/bash
/usr/bin/gfortran $(for i in ${CPATH//:/ }; do echo -I"$i"; done) "$@"
HERE
$ chmod a+x gfortran
Alternatively you can formulate it as a shell alias, but that would be less flexible and will not work in as many situations.
Problem
I have some Fortran code which uses included modules, and I am wondering what environment variables actually work to set the include path. To test this out I've been using one of the NAG example codes. This works: ``` $ gfortran e04ucfe.f90 -lnag_nag -I/opt/NAG/fll6a23dfl/nag_interface_blocks ``` This doesn't work: ``` $ export CPATH=/opt/NAG/fll6a23dfl/nag_interface_blocks $ gfortran e04ucfe.f90 -lnag_nag e04ucfe.f90:10.37: USE nag_library, ONLY : nag_wp 1 Fatal Error: Can't open module file 'nag_library.mod' for reading at (1): No such file or directory ``` However, the GCC/GFortran documentation states that: The gfortran compiler currently does not make use of any environment variables to control its operation above and beyond those that affect the operation of gcc. (see https://gcc.gnu.org/onlinedocs/gfortran/Environment-Variables.html and https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html#Environment-Variables) I've tried `ltrace`-ing the gfortran run and can see it looking at other environment variables (e.g. the regular `PATH`) but not `CPATH`. I can work around this with this: ``` gfortran e04ucfe.f90 -lnag_nag `echo -I$CPATH | sed -e 's/:/ -I/'` ``` ...but why is this necessary? `CPATH` works fine with gcc, including for other languages than C/C++, so why doesn't this work with gfortran? Is there something I can successfully use to the same effect as CPATH for gcc with gfortran, to avoid having to pass multiple `-I` arguments? Side note: `LIBRARY_PATH` works fine in a similar way, for replacing the `-L/path/to/libs` on the gfortran command-line.