File Input / Output

Here we will generate some data and write it to a file:

src/08_file_write.f90

! Program : Write output to a file

PROGRAM file_write
  IMPLICIT NONE

  INTEGER :: ii

  OPEN(unit=1, file='output.dat', status='new')
    DO ii = 1, 10
      WRITE(1, '(i4)') ii*ii
    ENDDO
  CLOSE(unit=1)
END PROGRAM file_write

info

Note that unit=0, 5, and 6 are reserved. Do not use them to identify files in your programs.

Reading from file: we will read the data from file that is generated in the above example.

src/09_file_read.f90

! Program : Read data from file

PROGRAM file_read
  IMPLICIT NONE

  INTEGER :: ii, data(10)

  OPEN(unit=1, file='output.dat', status='old')
    DO ii = 1, 10
      READ(1, '(i4)') data(ii)
    END DO
  CLOSE(unit=1)

  DO ii = 1, 10
    PRINT '(i3)', data(ii)
  END DO
END PROGRAM file_read