Getting input file in fortran

1

Hi there, I am trying to write a code so that fortran could display the input data from an input file. i get no errors after compiling, for when I run i get : Could not print backtrace: libbacktrace could not find executable to open. I appreciate your help in this matter.
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program main_prog

!> Include standard Fortran environment for IO
use iso_fortran_env, only : input_unit, error_unit
!> Won to obtain a command line arguments
use io_tools, only : read_argument

use scf_main, only : scf_prog
use print_matrix, only : write_vector, write_matrix

implicit none
integer, parameter :: wp = selected_real_kind(15)

character(len=:),allocatable :: input_file

!> Does the provided input file exist
logical :: exist

!> Unit for reading the input from
integer :: io_unit

!> Error status from opening file for IO
integer :: error

!> Error message from opening file for IO
character(len=256) :: message
    !> System specific data
!> Number of atoms
integer :: nat

!> Number of electrons
integer :: nel

!> Atom coordinates of the system, all distances in bohr
real(wp), allocatable :: xyz(:,:)

!> Nuclear charges
real(wp), allocatable :: chrg(:)

!> Number of basis functions
integer :: nbf

!> Slater exponents of basis functions
real(wp),allocatable :: zeta(:)

!> This code snippet optionally opens a file or allows reading from STDIN
!> In case of no command line arguments, you read from the STDIN
if (command_argument_count() == 0) then
    io_unit = input_unit
else

    !> In case there are command line arguments we obtain the first one
    call read_argument(1, input_file)
    !> Check if the argument corresponds to an existing file
    inquire(file=input_file, exist=exist)
    !> The file does not exist, we will return with a meaningful error message
    if (.not.exist) then
        write(error_unit, '("ERROR:", 1x, a)') &
            & "The input file '"//input_file//"' does not exist"
        error stop 1
    end if
    !> If the file exist, we open it to a new unit an pass it to the scf
    open(file= input_file , newunit=io_unit, status='old', &
        & iomsg=message, iostat=error)
    if (error /= 0) then
        write(error_unit, '("ERROR:", 1x, a)') trim(message)
        error stop 1
    end if
end if

call scf_prog(io_unit)

! The first line with three integers
read (io_unit, *) nat, nel, nbf
! The second line with floating-point numbers
read(io_unit,  *) xyz(:,:), xyz(:,:) , xyz(:,:) , chrg(:) , nbf
! The third line with floating-point numbers
read(io_unit, *) zeta(:)
!forth line
read(io_unit,  *) xyz(:,:), xyz(:,:) , xyz(:,:) , chrg(:) , nbf
!fifth line
read(io_unit, *) zeta(:)
! Display the read values
write(*,*)  nat,  nel , nbf
write(*,*)  xyz(:,:), xyz(:,:) , xyz(:,:) , chrg(:), nbf
write(*, *) zeta(:)
write(*,*)  xyz(:,:), xyz(:,:) , xyz(:,:) , chrg(:), nbf
write(*, *) zeta(:)

!> If we have opened a file, we have to cleanup now, so we close it again
if (io_unit /= input_unit) then
    close(io_unit)
end if

end program main_prog

2

Welcome to the forum.

To help us help you, it would be useful if you post a complete program. The subroutine read_argument is not shown, nor the declarations of various variables. You should also show what is going wrong - the output to screen and how you invoke the program, as now we have to guess ;).

3

Hi Arjen, thanks for your message, I have edited it. I compile it with Make/fpm and I get no errors. But when I run it with ./scf , it doesnt show the input data. here is also my input data:
2 2 2
0.0 0.0 -0.7 1.0 1
1.20
0.0 0.0 0.7 1.0 1
1.20

4

But how does the program know the input file? Or do you read the data from standard input?

5

Oh, but the arrays you read are not allocated. I guess nat, nel and nbf define array dimensions? Allocation in this way is not automatic.