compilers, English, fortran, language, llenguatge

Tagged fortran, howto, namelist

How to read arrays on a Namelist

by lincador 24/03/2025 27

Fortran namelist is a I/O method introduced in Fortran 77. It later became a standard in Fortran 90. It basically allows to read/write data as a dictionary like in plain text files.

In order to read a REAL array, see the example below:

program exnamelist
  implicit none
  integer :: nrows,ncol
  real:: values(4)
  character (len=100) :: data_file
  namelist /param/ nrows,ncol,data_file,values
  open (unit=20,file="param.nml")
  read (20,nml=param)
  write(*,*) "values=", values
end program exnamelist

Input param.nml:

&param
  nrows=3,
  ncol=2,
  data_file="hello.txt",
  values=1.1, 2.2, 3.3, 4.4
/

Output:

mymachine:~/tests/namelist_arrays$ ./a.out 
 values=   1.10000002       2.20000005       3.29999995       4.40000010