open_csv_file Subroutine

    subroutine open_csv_file(me,filename,n_cols,status_ok,append)

    implicit none

    class(csv_file),intent(inout)   :: me
    character(len=*),intent(in)     :: filename     !! the CSV file to open
    integer,intent(in)              :: n_cols       !! number of columns in the file
    logical,intent(out)             :: status_ok    !! status flag
    logical,intent(in),optional     :: append       !! append if file exists

    integer :: istat       !! open `iostat` flag
    logical :: append_flag !! local copy of `append` argument
    logical :: file_exists !! if the file exists

    ! clear existing data:
    if (allocated(me%csv_data)) deallocate(me%csv_data)
    if (allocated(me%header))   deallocate(me%header)

    me%n_cols = n_cols

    ! optional append argument:
    append_flag = .false.
    file_exists = .false.
    if (present(append)) then
        append_flag = append
        if (append) inquire(file=filename, exist=file_exists)
    end if

    if (append_flag .and. file_exists) then
        open(newunit=me%iunit,file=filename,status='OLD',position='APPEND',iostat=istat)
    else
        open(newunit=me%iunit,file=filename,status='REPLACE',iostat=istat)
    end if

    if (istat==0) then
        status_ok = .true.
    else
        if (me%verbose) write(error_unit,'(A)') &
                            'Error opening file: '//trim(filename)
        status_ok = .false.
    end if

    end subroutine open_csv_file