Smart printing of integers in fortran90

Question

I'm learning Fortran90 after a brief introduction to Fortran77 a few years ago. When printing integers in Fortran, you must specify how many spaces you want to reserve for printing the integer. Consider this program...

implicit none

integer :: i
i = 123

write(*, '(A, I3, A)')  "'", i, "'"  !3 spaces for output = no padding
write(*, '(A, I5, A)')  "'", i, "'"  !5 is too many, so output is padded
write(*, '(A, I2, A)')  "'", i, "'"  !2 is too few, so output is jibberish
write(*, '(A, I:, A)')  "'", i, "'"  !Default behavior

end program

...which generates the following output.

'123'
'  123'
'**'
'         123'

How do I allocate the correct amount of space for integer printing when I do not know how many digits are in the integer?

Update: If your compiler is F95-compliant, you can use the I0 edit descriptor (i.e., put '(A, I0, A)' for the second argument of the write function in my example above. Thanks @janneb!

Answer 1

Use the I0 edit descriptor. Well, to be pedantic IIRC that is Fortran 95, so if you're really strict about no more than F90, then I suppose this won't work.