How can I read the number of lines in Fortran 90 from a text file?

Question

How can I read the number of lines present in a text file?

My text file seems to be like:

1
2
3
.
.
.
n

Answer 1

Use:

nlines = 0
OPEN (1, file = 'file.txt')
DO
    READ (1,*, END=10)
    nlines = nlines + 1
END DO
10 CLOSE (1)

print*, nlines

end

Or:

nlines = 0
OPEN (1, file = 'file.txt')
DO
  READ(1,*,iostat=io)
  IF (io/=0) EXIT
  nlines = nlines + 1
END DO
CLOSE (1)

print*, nlines