I am used to Fortran in which I used the namelist sequential read in to get variables out of a file. This allows me to have a file which looks like this
&inputDataList
n = 1000.0 ! This is the first variable
m = 1e3 ! Second
l = -2 ! Last variable
/
where I can name the variable by it's name and assign a value as well as comment afterwards to state what the variable actually is. The loading is done extremely easy by
namelist /inputDataList/ n, m, l
open( 100, file = 'input.txt' )
read( unit = 100, nml = inputDataList )
close( 100 )
Now my question is, is there any similar thing in C? Or would I have to do it manually by chopping the string at the '=' and so on?
Here is a simple example that will let you read Fortran namelists from C. I used the namelist file that you provided in the question, input.txt
.
Fortran subroutine nmlread_f.f90
(notice the use of ISO_C_BINDING
):
subroutine namelistRead(n,m,l) bind(c,name='namelistRead')
use,intrinsic :: iso_c_binding,only:c_float,c_int
implicit none
real(kind=c_float), intent(inout) :: n
real(kind=c_float), intent(inout) :: m
integer(kind=c_int),intent(inout) :: l
namelist /inputDataList/ n,m,l
open(unit=100,file='input.txt',status='old')
read(unit=100,nml=inputDataList)
close(unit=100)
write(*,*)'Fortran procedure has n,m,l:',n,m,l
endsubroutine namelistRead
C program, nmlread_c.c
:
#include <stdio.h>
void namelistRead(float *n, float *m, int *l);
int main()
{
float n;
float m;
int l;
n = 0;
m = 0;
l = 0;
printf("%5.1f %5.1f %3d\n",n,m,l);
namelistRead(&n,&m,&l);
printf("%5.1f %5.1f %3d\n",n,m,l);
}
Also notice that n
,m
and l
need to be declared as pointers in order to pass them by reference to the Fortran routine.
On my system I compile it with Intel suite of compilers (my gcc and gfortran are years old, don't ask):
ifort -c nmlread_f.f90
icc -c nmlread_c.c
icc nmlread_c.o nmlread_f.o /usr/local/intel/composerxe-2011.2.137/compiler/lib/intel64/libifcore.a
Executing a.out
produces the expected output:
0.0 0.0 0
Fortran procedure has n,m,l: 1000.000 1000.000 -2
1000.0 1000.0 -2
You can edit the above Fortran procedure to make it more general, e.g. to specify namelist file name and list name from the C program.
I've made a test of above answer under GNU compilers v 4.6.3 and worked perfectly for me. Here's is what I did for the corresponding compilation:
gfortran -c nmlread_f.f90
gcc -c nmlread_c.c
gcc nmlread_c.o nmlread_f.o -lgfortran
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