init

Author: scivision

file_or_console_output.f90

@@ -0,0 +1,28 @@
+program file_or_console
+use, intrinsic:: iso_fortran_env, only: stdout=>output_unit
+
+implicit none
+
+character(:), allocatable :: filename
+character(256) :: buf
+integer :: i, u
+
+call get_command_argument(1,buf,status=i)
+if (i==0) then
+  filename = trim(buf)  ! Fortran 2003 auto-allocate
+  print *, 'writing to ',filename
+  open(newunit=u, file=filename, form='formatted')
+else
+  u = stdout
+endif
+
+i = 3 ! test data
+
+write(u,*) i, i**2, i**3
+
+if (u /= stdout) close(u)   ! closing stdout can disable text console output
+ 
+print *,'goodbye'
+
+! end program implies closing all file units, but here we close in case you'd use in subprogram (procedure), where the file reference would persist.
+end program