get_memory_info Subroutine

   subroutine get_memory_info(mem_free, mem_total)
   !< Get the current CPU-memory status.
   !< @NOTE Currently implemented only per Unix/Linux based systems. Return -1 if failing.
   !<```fortran
   !< use penf
   !< real(R8P), allocatable :: a(:,:,:)
   !< integer(I8P)           :: mem_free_1, mem_free_2, mem_total
   !< logical                :: is_present
   !< integer(I4P)           :: n, i, j, k
   !< call get_memory_info(mem_free_1, mem_total)
   !< inquire(file='/proc/meminfo', exist=is_present)
   !< if (is_present) then
   !<    n = 800
   !<    allocate(a(1:n,1:n,1:n))
   !< else
   !<    print*, .true.
   !<    stop
   !< endif
   !< a = 1._R8P
   !< do k=2, n
   !< do j=2, n
   !< do i=2, n
   !<    a(i,j,k) = 1._R8P / 2._R8P * exp(a(i-1,j,k)) - a(i-1,j,k)
   !< enddo
   !< enddo
   !< enddo
   !< call get_memory_info(mem_free_2, mem_total)
   !< print*, mem_free_1 > mem_free_2
   !<```
   !=> T <<<
   integer(I8P), intent(out) :: mem_free   !< Free memory.
   integer(I8P), intent(out) :: mem_total  !< Total memory.
   logical                   :: is_present !< Logical flag to check the presence of '/proc/meminfo' system file.
   integer(I4P)              :: file_unit  !< File unit.
   character(999)            :: line       !< Line buffer.

   mem_free  = -1_I8P
   mem_total = -1_I8P
   inquire(file='/proc/meminfo', exist=is_present)
   if (is_present) then
      open(newunit=file_unit, file='/proc/meminfo', status='old')
      read(file_unit, '(A)') line ! total memory
      call parse_line(l=line, v=mem_total)
      read(file_unit, '(A)') line ! free memory
      call parse_line(l=line, v=mem_free)
      close(file_unit)
   endif
   contains
      subroutine parse_line(l,v)
      !< Parse input line and return memory value.
      character(*), intent(in)  :: l      !< Input line.
      integer(I8P), intent(out) :: v      !< Memory value.
      integer(I4P)              :: colon  !< Index of colon (name/value separator) char in line.
      character(:), allocatable :: memval !< Memory value, string.

      colon = index(l, ':')                 ! find name/value separator position
      memval = trim(adjustl(l(colon+1:)))   ! get memory value, string
      memval = trim(memval(:len(memval)-2)) ! remove memory unit, e.g. kb
      v = cton(str=memval, knd=1_I8P)       ! cast to string to integer
      endsubroutine parse_line
   endsubroutine get_memory_info