Output of a fortran program into a variable

Question

I have an interactive FORTRAN program that requires various inputs from the user. Now, I want to store the output of this Fortran program into a variable and use this value in a shell script. I tried

 var=`./test` and var=$(./test)

but in both the cases, it does not prompt the user for input and stays idle. What should I do? A piece of example fortran code is like this

  test.f  

  program test
  character*1 resp1, resp3
  integer resp2, ans

  write(*,*) 'Think of a prime number less than 10'
  write(*,*) 'Say whether it is odd or even'
  write(*,*) 'Write o/e'
  read(*,*) resp1
  if ( resp1 .EQ. 'e' ) then
   ans=2
  else
   write(*,*) 'Is the number close to 4 or 8'
   read (*,*) resp2
   if ( resp2 == 8 ) then
    ans=7
   else
    write(*,*) 'Is the number greater than or less than 4'
    write(*,*) 'Write g or l'
    read (*,*) resp3
    if ( resp3 .EQ. 'l' ) then
     ans=3
    else
     ans=5
    end if
   end if
  end if
  write(*,*) ans
  end

  Compiled as gfortran test.f -o test

Then I used a script like this

 test.sh

 var=`./test`
 echo "The answer you are looking for is " $var

I believe there is something very trivial that I am not able to find. Please help me.

P.S. This is just an example code and script and my actual script and code is far different.

Prompt output and variable output are merged. Not sure if that is possible but could you prompt the user on standard error instead of standard output? That would work. — Jean-François Fabre, Oct 25 '16 at 12:05
I highly encourage you to write free-form Fortran instead. See: http://www.fortran90.org/src/best-practices.html — jlokimlin, Oct 25 '16 at 21:46
I am learning but I will definitely try to follow the conventions. — Himangshu Paul, Oct 25 '16 at 23:33

score 3 · Accepted Answer · answered Oct 25 '16 at 12:09

3

Jean-François Fabre is right.

program test 
character*1 resp1, resp3 
integer resp2, ans 

write(0,*) 'Think of a prime number less than 10' 
write(0,*) 'Say whether it is odd or even' 
write(0,*) 'Write o/e' 
read(5,*) resp1 
if ( resp1 .EQ. 'e' ) then 
 ans=2 
else 
 write(0,*) 'Is the number close to 4 or 8' 
 read (5,*) resp2 
 if ( resp2 == 8 ) then 
  ans=7 
 else 
  write(0,*) 'Is the number greater than or less than 4' 
  write(0,*) 'Write g or l' 
  read (5,*) resp3 
  if ( resp3 .EQ. 'l' ) then 
   ans=3 
  else 
   ans=5 
  end if 
 end if 
end if 
write(6,*) ans 
end

Questions are stderr (0), Answers are stdin (5), Result is stdout (6)

var=`./test`

works fine after that.

answered Oct 25 '16 at 12:09

Eric Duminil

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0, 5 and 6? Just out of curiosity, what are 1, 2, 3 and 4? – James Brown Oct 25 '16 at 12:10
1

Thanks so much. It works. I always used write(*,*). I realized today the importance of the numbers within. – Himangshu Paul Oct 25 '16 at 12:16
1

@JamesBrown : As far as I know, they can be defined to be files. 0,5 and 6 is just an old convention, pretty much like everything else in Fortran :D https://en.wikipedia.org/wiki/Standard_streams – Eric Duminil Oct 25 '16 at 12:17
1

Probably a card deck reader, and a chisel and tablet... And not a Samsung tablet, but a Flintstone's tablet. – Holmz Oct 25 '16 at 20:57
3

Use of the ERROR_UNIT, OUTPUT_UNIT and INPUT_UNIT named constants from the ISO_FORTRAN_ENV intrinsic module, rather than the integer literal values, will be more robust and portable, though there is no requirement that output to ERROR_UNIT be distinct from OUTPUT_UNIT. – IanH Oct 25 '16 at 21:40

Output of a fortran program into a variable

1 Answers1